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BOOK 160.J639 V JOHNSON # LOGIC

3

2

c.

1

T153 OOOOMTDS

fi

LOGIC PART

II

CAMBRIDGE UNIVERSITY PRESS CLAY, Manager

C. F.

LONDON

:

FETTER LANE,

E.C. 4

NEW YORK THE MACMILLAN :

CO.

BOMBAY CALCUTTA I MACMILLAN AND CO., Ltd. MADRAS ] TORONTO THE MACMILLAN CO. OF \

:

CANADA,

Ltd.

TOKYO MARUZEN-KABUSHIKI-KAISHA :

ALL RIGHTS RESERVED

Be

LOGIC PART

II

DEMONSTRATIVE INFERENCE DEDUCTIVE AND INDUCTIVE

BY

W.

E.

JOHNSON, M.A.

FELLOVl^ OF king's COLLEGE, CAMBRIDGE, SIDGWICK LECTURER IN MORAL SCIENCE IN THE

UNIVERSITY OF CAMBRIDGE

CAMBRIDGE AT THE UNIVERSITY PRESS 1922

'^\

.0-

CONTENTS INTRODUCTION PAGE §

I.

Application of the term

'

substantive

§

2.

Application of the term

'

adjective

§ 3.

Terms '

'

and

'

adjective

Epistemic character of assertive

§ 5.

The given presented under The paradox of implication '

*

.

'

.

.

.

.

.

.

'........... ...... .... ........ ......

' substantive universal

§ 4.

§ 6.

xi

'

'

contrasted with

'

particular

'

and

tie

.

certain determinables

§ 7. Defence of Mill's analysis of the syllogism

CHAPTER

xii

xiii

xiv xiv

xv xvii

I

INFERENCE IN GENERAL §

I.

...... .......

Implication defined as potential inference

% 2. Inferences involved in the processes of perception

and epistemic conditions for valid of the 'paradox of inference'

§ 3. Constitutive § 4.

The

and association inference. Examination .

Applicative and Implicative principles of inference

§ 5. Joint

employment of these

principles in the syllogism

§ 6.

Distinction between applicational and implicational universals. structural proposition redundant as minor premiss

§ 7.

Definition of a logical category in terms of adjectival determinables

§ 8. Analysis of the syllogism in terms of assigned determinables. illustrations of applicational universals . .

§ 9. § 10.

i

2

How

identity

The

may be

said to

be involved

in

.

.

every proposition

The

Further .

.

.17

.

20

formal principle of inference to be considered redundant as major premiss. Illustrations from syllogism, induction, and mathematical equality

............ ............

20

§11. Criticism of the alleged subordination of induction under the syllogistic principle

24

CONTENTS

vi

CHAPTER

II

THE RELATIONS OF SUB-ORDINATION AND CO-ORDINATION AMONGST PROPOSITIONS OF DIFFERENT TYPES §

I.

The

Counter-applicative and Counter-implicative principles required axioms of Logic and Mathematics . .

.... ....

27

in the philosophy of thought

31

for the establishment of the

§

z.

Explanation of the Counter-applicative principle

§3. Explanation of the Counter-implicative principle § 4.

§

5.

Significance of the

two inverse principles

........... .......

of super-ordination, sub-ordination and co-ordination amongst propositions

Scheme

scheme

§ 6. Further elucidation of the

CHAPTER

28

29

32

38

III

SYMBOLISM AND FUNCTIONS §1.

The

§ 2.

The

value of symbolism. Illustrative and shorthand symbols. Classification of formal constants. Their distinction from material constants .

system § 3.

§ 4.

....

41

nature of the intelligence required in the construction of a symbolic

44

The range

of variation of illustrative symbols restricted within some logical category. Combinations of such symbols further to be interpreted as belonging to an understood logical category. Illustrations of intelligence required in working a symbolic system

Explanation of the term

'

function,'

and of the

'

....

46

for a function

48

variants

'

§ 5. Distinction between fvinctions for which all the material constituents are variable, and those for which only some are variable. Illustrations

from logic and arithmetic § 6.

§

7.

The

......... .... ...... .....

various kinds of elements ofform in a construct

Conjunctional and predicational functions

§ 8.

Connected and unconnected sub-constructs

§ 9.

The

use of apparent variables in symbolism for the representation of the distributives every and some. Distinction between apparent variables and class-names

..........

50 53 55 57

58

§ 10. Discussion of compound symbols which do and which do not represent genuine constructs . . . .

§ It. Illustrations of

§12. Criticism of functions

genuine and

Mr

.

.

.

fictitious constructs

Russell's view of the relation

and the functions of mathematics

......61 ..... .... .

.

64

between propositional

§13. Explanation of the notion of a descriptive function § 14. Further criticism of Mr Russell's account of propositional functions §15. Functions of two or more variants

66

69

.

71

73

CONTENTS

CHAPTER

vii

IV

THE CATEGORICAL SYLLOGISM

.......-77 .......

PAGE

§

r.

Technical terminology of syllogism

§

2.

Dubious propositions to

76

illustrate syllogism

§3. Relation of syllogism to antilogism

.

.

.

.

78

.....

§ 4.

Dicta for the first three figures derived from a single antilogistic dictum, showing the normal functioning of each figure

§ 5.

Illustration of philosophical

§ 6.

arguments expressed in

form

§ 7.

The

§ 8.

Special rules and valid

all

the propositions

propositions of restricted and unrestricted form in each figure

§ 9. Special rules

and

valid

moods moods

for the fourth figure

§11. Proof of the rules necessary for rejecting invalid syllogisms.

.

of quality

84

... ....

for the first three figures

.

Summary

83

.

§ lo. Justification for the inclusion of the fourth figure in logical doctrine

§ 12.

79 81

.

...........

Re-formulation of the dicta for syllogisms in which are general

syllogistic

.

............ .... .......... .... ........... .........

of above rules; and table of

moods unrejected by

85 87

88 89

the rules

92

§13. Rules and tables of unrejected moods for each figure § 1 4. Combination of the direct and indirect methods of establishing the valid moods of syllogism

93

96

§15. Diagram representing the valid moods of syllogism § 16.

The

§ 17. Reduction of irregularly formulated arguments to syllogistic form § 18.

97

Sorites

97 98

.

Enthymemes

§19. Importance of syllogism

roo 102

CHAPTER V FUNCTIONAL EXTENSION OF THE SYLLOGISM §

I.

§ 2.

Deduction goes beyond mere subsumptive inference, when the major . . 103 premiss assumes the form of a functional equation. Examples functional equation is a universal proposition of the second order, the . . .105 functional formula constituting a Law of Co- variation.

A

§ 3.

The solutions of mathematical equations which yield single-valued func. . tions correspond to the reversibility of cause and effect

§ 4.

Significance of the

§

5.

§ 6.

.106

number of variables entering body falling in vacuo

into a functional formula

Example of a The logical characteristics of connectional equations illustrated by thermal .

.

.

.

.

.

.

108 1

10

. .111 and economic equilibria The method of Residues is based on reversibility and is purely deductive 1 16 . 119 §8. Reasons why the above method has been falsely termed inductive .

§

.

.

.

.

.

.

7.

§ 9.

Separation of the subsumptive from the functional elements in these . . . extensions of syllogism .

.

.

.

.

.120

vm

CONTENTS

CHAPTER

VI

FUNCTIONAL DEDUCTION §1. In the deduction of mathematical and logical formulae, new theorems are established for the different species of a genus, which do not hold for the genus . . .123

....... .........

.

.

§2. Explanation of the Aristotelean

.

.

.

.

.

.

tdiov

125

§3- In functional deduction, the equational formulae are non-limiting.

Elementary examples §4-

126

The range

of universality of a functional formula varies with the number of independent variables involved. Employment of brackets. Importance of distinguishing between connected and disconnected compounds

128

The

functional nature of the formulae of algebra accounts for the possibility of deducing new and even wider formulae from previously established and narrower formulae, the Applicative Principle alone being

employed

.

.

.

.

§6. Mathematical Induction

§7.

The

logic of

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

mathematics and the mathematics of logic

§8. Distinction between premathematical and mathematical logic

-130 -133 -135 .138

.

§9- Formal operators and formal relations represented by shorthand and not variable symbols. Classification of the main formal relations according to theis properties . . . .141 .

.

.

The material variables

§ Il-

.

.

...... ...... .....

of mathematical and logical symbolisation receive specific values only in concrete science

144

Discussion of the Principle of Abstraction

145

The

magnitude are not determinates of the single determinable Magnitude, but are incomparable ls-

specific kinds of

150

The

logical symbolic calculus establishes y^rwMto of implication which are to be contrasted with the principles of inference employed in the

procedure of building up the calculus

.

.

.

.

.

-151

.

CHAPTER Vn THE DIFFERENT KINDS OF MAGNITUDE §

I.

§ 2.

The terms

'greater' and 'less' predicated of magnitude, 'larger' 'smaller' of that which has magnitude

Integral

number

and

as predicable of classes or enumerations

§ 3. Psychological exposition of counting

.

§ 4. Logical principles underlying counting § 5. One-one correlations for finite integers

153

154 155 158

160

§ 6.

Definition of extensive magnitude

161

§

Adjectival stretches compared with substantival

163

7.

.... .......

§ 10.

Comparison between extensive and extensional wholes Discussion of distensive magnitudes Intensive magnitude

172

§ II.

Fundamental

173

§ 8. § 9.

distinction

between distensive and intensive magnitudes

166 168

CONTENTS

ix

PAGE §12. The problem of equality of extensive wholes

174

§ 13. Conterminus spatial and temporal wholes to be considered equal, quali tative stretches only comparable by causes or effects

175

.

....

Complex magnitudes derived by combination of simplex §15. The theory of algebraical dimensions § 16. The special case in which dividend and divisor are quantities same kind § 14.

.

.........

§

1

7.

Summary

of the above treatment of magnitude

CHAPTER

180 185 of the

186 187

.

VIII

INTUITIVE INDUCTION The general antithesis between induction and deduction The problem of abstraction §3. The principle of abstractive or intuitive induction

§

t.

§ 2.

.

.

.

.

.

.

.

.

.

.189 .

.

.

§4. Experiential and formal types of intuitive induction §5. Intuitive induction involved in introspective and ethical judgments § 6. Intuitive inductions upon sense-data and elementary algebraical and .

logical relations

.

.

.

.

.

§7. Educational importance of intuitive induction

CHAPTER

.

.

.

.

.

.

.

.

1

90

.191

.... .

192

193

'194 .196

IX

SUMMARY INCLUDING GEOMETRICAL INDUCTION Summary Summary

induction reduced to

§ 2.

§ 3.

Summary

induction involved in geometrical proofs

§ 4.

Explanation of the above process

§ 5.

Function of the figure

§.6.

Abuse of

§

I

first

figure syllogism

197

.

..... ...... .... ..... .....

induction as establishing the premiss for induction proper. Criticism of Mill's and Whewell's views

1

98

200 201

in geometrical proofs

203

the figure in geometrical proofs

205

208

§7. Criticism of Mill's 'parity of reasoning'

CHAPTER X DEMONSTRATIVE INDUCTION §

I.

Demonstrative induction uses a composite along with an instantial premiss . . .210 .

.

.

.

.

.

.

.

arguments leading up

.

§ 2.

Illustrations of demonstrative

§ 3.

Conclusions reached by the conjunction of an alternative with a junctive premiss . . . . .

induction

.

.

.

.

.

.

.

.

.

.

to demonstrative .

.

.

.

.210 dis-

.214 as

CONTENTS

X

PAGE §4.

The formula

of direct univcrsalisation

§5. Scientific illustration of the above

....... .

.

.

.

.

.215

§

7.

§8.

217

of others

csiS

The

.

.

.

.

.

.

.

Figure of Agreement

.

.

.

.

.

.......... .......... ......... ......... .....

four figures of demonstrative induction

§ 9. Figure of Difference § 10.

216

methods of induction The major premiss for demonstrative induction as an expression of the dependence in the variations of one phenomenal character upon those

§ 6. Proposed modification of Mill's exposition of the

.

.

.

.

.221 222

223

§11. Figure of Composition

224

§12. Figure of Resolution

226

.

......

§13. The Antilogism of Demonstrative Induction §14. Illustration of the Figure of Difference §15. Illustration of the Figure of Agreement § 16.

.

.

.

.

.

.

.

.

§ 17. Modification of symbolic notation in the figures where different cause. factors represent determinates under the same determinable .

§ 18. § 19.

228

•'^31

Principle for dealing with cases in which a number both of cause-factors effect-factors are considered, with a symbolic example

and

226

232

234

between the two last and the two first figures Explanation of the distinction between composition and combination

235

of cause-factors

235

The

striking distinction

.

.

..........

§20. Illustrations of the figures of Composition and Resolution

CHAPTER

.

.

.

237

XI

THE FUNCTIONAL EXTENSION OF DEMONSTRATIVE INDUCTION

....... '............ ..........

The major

premiss for Demonstrative Induction must have been estabby Problematic Induction 240 .241 §2. Contrast between my exposition and Mill's .242 § 3. The different uses of the term hypothesis in logic §4. Jevons's confusion between the notions 'problematic' and 'hypothetical 244 §

I.

lished

.

'

§ 5.

The

'

.

.

.

.

.

.

establishment of a functional formula for the figures of Difference

and of Composition § 6.

The

formula §

7.

A

............ ............

criteria of simplicity

comparison of

these

and analogy

criteria

with similar criteria proposed

formula

INDEX

methods

for

249

by

Whewell and Mill

§ 8. Technical mathematical

246

for selection of the functional

251

determining the most probable 252

254

INTRODUCTION TO PART §

in

Before introducing the

I.

Part II,

I

topics to be

II

examined

propose to recapitulate the substance of

Part I, and in so doing to bring into connection with one another certain problems which were there treated I hope thus to lay different emsome of the theories that have been mainand to remove any possible misunderstandings

in different chapters.

phasis upon tained,

where the treatment was unavoidably condensed. In my analysis of the proposition I have distinguished the natures of substantive and adjective in a form intended to accord in essentials with the doctrine of the large majority of logicians, is

new its

and as

far as

my terminology

novelty consists in giving wider scope to each

of these two fundamental terms. Prima facie it might be supposed that the connection of substantive with adjective in the construction of a proposition

mount

is

tanta-

to the metaphysical notions of substance

inherence.

But

my

notion of substantive

and

intended

is

to include, besides the metaphysical notion of substance

— so

far as this

can be philosophically justified

tion of occurrences or events to

—the no-

which some philosophers

of the present day wish to restrict the realm of reality.

Thus by

a substantive /r^/^r

the category of the existent

I

is

mean an

and divided into the two existent;

subcategories: what continues to exist, or the continuant;

and what ceases

to exist, or the occurrent,

rent being referrible to a continuant.

To

every occurexist

is

to be

INTRODUCTION

xii

in

temporal or spatio-temporal relations to other exis-

and these relations between existents are the

tents;

A

fundamentally external relations. cannot characterise, but

is

substantive proper

necessarily characterised

;

on

other hand, entities belonging to any category whatever (substantive proper, adjective, proposition,

the

etc.)

may be

characterised by adjectives or relations

belonging to a special adjectival sub-category corresponding, in each case, to the category of the object

which

it

characterises.

Entities, other than substantives

proper, of which appropriate adjectives can be predicated, function as quasi-substantives.

The term

§ 2.

a wider range than usual, for that

it

my

adjective, in it is

application, covers

essential to

my system

There are two

should include relations.

distinct

points of view from which the treatment of a relation as of the

same

defended.

logical nature as an adjective

In the

first

a relational proposition

may be

place the complete predicate in is,

in

my

view, relatively to the

subject of such proposition, equivalent to an adjective in the '

He

is

ordinary sense.

For example,

in

afraid of ghosts,' the relational

pressed by the phrase 'afraid

of

;

the proposition,

component

is

ex-

but the complete

predicate 'afraid of ghosts' (which includes this relation)

has

all

the logical properties of an ordinary adjective,

so that for logical purposes there tinction

between such a

tional predicate.

component it

in

is

no fundamental

relational predicate

In the second place,

such a proposition

is

if

and an

disirra-

the relational

separated,

I

hold that

can be treated as an adjective predicated of the sub-

stantive-couple 'he' and 'ghosts'. In other words, a relation cannot be identified with a class of couples,

i.e.

be

INTRODUCTION conceived extensionally

;

xiU

but must be understood to

be conceived intensionally. It no controvertible problem thus to include relations under the wide genus adjectives. It is compatible, for example, with almost the whole of Mr characterise couples,

seems

to

me

i.e.

to raise

Russell's treatment of the proposition in his Principles of

Mathematics-, and, without necessarily entering into the

emerge in such philosophical discussions, I hold that some preliminary account of relations is required even in elementary logic. My distinction between substantive and adjec§ 3. tive is roughly equivalent to the more popular philosophical antithesis between particular and universal; the Thus I notions, however, do not exactly coincide. controvertible issues that

understand the philosophical term particular not to apply to quasi-substantives, but to be restricted to substantives

even more narrowly to occurrents. On the other hand, I find a fairly unanimous opinion in favour of calling an adjective predicated of proper,

existents, or

i.e.

a particular subject, a particular

—the

name

universal

being confined to the abstract conception of the adjective. Thus red or redness, abstracted from any specific

judgment,

is

manifested

in

held to be universal;

a particular object of perception, to be

Furthermore, qua particular, the ad-

itself particular.

jective

is

but the redness,

said to be an existent, apparently in the

sense as the object presented to perception tent.

To me

it is

difficult to

a factor

I

regard

in the real

jectively real

is

it ;

an

same exis-

argue this matter because,

while acknowledging that an adjective universal,

is

may be

called a

not as a mere abstraction, but as

and hence,

in

holding that the ob-

properly construed into an adjective

INTRODUCTION

xiv

characterising a substantive, the antithesis between the

and the universal (i.e. in my terminology between the substantive and the adjective) does not

particular

involve separation within the

for thought,

in the

real,

but solely a separation

sense that the conception of the

substantive apart from the adjective, as well as the

conception of the adjective apart from the substantive, equally entail abstraction. § 4.

Again, taking the whole proposition constituted

by the connecting of substantive with maintained that tion

is

to

adjective,

have

I

in a virtually similar

sense the proposi-

be conceived as abstract.

But, whereas the

characterising

may be

tie

called constitutive in

its

func-

tion of connecting substantive with adjective to construct the proposition, tie

I

have spoken of the assertive

as epistemic, in the sense that

it

connects the thinker

with the proposition in constituting the unity which

may

be called an act of judgment or of assertion. When, however, this act of assertion becomes in its turn an object of thought,

the existent

for

;

it is

conceived under the category of

such an act has temporal relations to

other existents, and

is

necessarily referrible to a thinker

Though, relatively to the primary proposition, the assertive tie must be conceived conceived as a continuant. as epistemic

;

yet, relatively to the

secondary proposition

which predicates of the primary that

by A, the

it

has been asserted

assertive tie functions constitutively.

In view of a certain logical condition presup§ 5. posed throughout this Part of my work, I wish to re-

mind the reader of

that aspect of

proposition, according to which

that which

is

I

my

analysis of the

regard the subject as

given to be determinately characterised

INTRODUCTION

Now

by thought.

characterised by

I

some

xv

hold that for a subject to be

it must have been presented as characterised by the corresponding adjectival determinable. The fact that what is given is characterised by an adjectival determinable

adjectival determinate,

first

is

constitutive

characterised

;

but the fact that

is

it is presented as thus Thus, for a surface to be

epistemic.

characterised as red or as square,

been constructed

it

must

first

have

thought as being the kind of thing that has colour or shape for an experience to be in

;

characterised as pleasant or unpleasant,

have been constructed that has hedonic tone.

in

it

must

first

thought as the kind of thing

Actually what

is given, is to be determined with respect to a conjunction of several specific aspects or determinates and these determine the category to which the given belongs. For example, ;

'

'

on the dualistic view of reality, the physical has to be determined under spatio-temporal determinables, and the psychical under the determinable consciousness or

same being can be characterised as two-legged and as rational, he must be put into the experience.

If the

category of the physico-psychical.

The passage from

§ 6.

those in Part

II, is

tion to inference.

Part

I,

as

was

it

tion.

topics treated in Part

I

to

equivalent to the step from implica-

The term

inference, as introduced in

did not require technical definition or analysis,

It

sufficiently well

understood without explana-

was, however, necessary in Chapter III to in-

dicate in outline one technical difficulty connected with

the paradox of implication and there I what will be comprehensively discussed ;

chapter of this Part, that implication

is

first

in

hinted,

the

first

best conceived

INTRODUCTION

xvi

While

as potential inference.

implication and inference

for

elementary purposes

may be regarded as

practically

was pointed out in Chapter III that there is nevertheless one type of limiting condition upon which depends the possibility of using the relation of implica-

equivalent,

it

tion for the purposes of inference.

Thus

reference to

the specific problem of the paradox of implication

was

unavoidable

in Part I, inasmuch as a comprehensive account of symbolic and mechanical processes necessarily

included reference to

all

possible limiting cases; but,

apart from such a purely abstract treatment, no special logical

importance was attached to the paradox.

The

was that of the permissible employment of the compound proposition 'If/> then ^,'in the limiting case referred to

unusual circumstance where knowledge of the truth or the falsity oi p or of ^ was already present

when

the com-

pound proposition was asserted. This limiting case will not recur in the more important developments of inferwill be treated in the present part of my logic. might have conduced to greater clearness if, in Chapters III and IV, I had distinguished when using the phrase implicative proposition between the primary and secondary interpretations of this form of proposition. Thus, when the compound proposition Tf/ then q' is rendered, as Mr Russell proposes, in the form 'Either not-/ or q^ the compound is being treated as a primary proposition of the same type as its components / and q. When on the other hand we substitute for Tf / then q' the phrase 'p implies q^ or preferably 'p would imply q^ the proposition is no longer primary, inasmuch

ence that It

—

as

it

—

predicates about the proposition q the adjective

'implied

by/' which renders

the

compound

a secondary

INTRODUCTION

xvu

proposition, in the sense explained in Chapter

V\ Now

I

whichever of these two interpretations is adopted, the is legitimate under certain limiting conditions is the same. Thus given the compound Either inference which

'

not-/ or q' conjoined with the assertion of infer

'

q

we

'/,'

could

just as given 'p implies q' conjoined with the

\

assertion of

'/,'

we

infer ^q!

reason that

It is for this

become merged into one the ordinary symbolic treatment of compound pro-

the two interpretations have in

and

positions;

normal cases no distinction

in

is

made

regard to the possibility of using the primary or secondary interpretation for purposes of inference. The in

normal

case,

however, presupposes that

entertained hypothetically;

when

this

the danger of petitio principii enters.

Part

it

was only a very

I

which

this fallacy

will

special

p

does not obtain,

The problem

and technical case

has to be guarded against

be dealt with

in its

and q are

;

in

more concrete and

Part

in

in II,

philoso-

phically important applications. § 7.

The mention

of this fallacy immediately sug-

gests Mill's treatment of the functions and value of the

syllogism; but, before discussing his views, to consider

what

charge of petitio

I

propose

main purpose was in tackling the principii that had been brought against his

the whole of formal argument, including in particular the syllogism.

In the

first

section of his chapter, Mill

—

two opposed

classes of philosophers the one regarded syllogism as the universal type of all logical reasoning, the other of whom regarded syllogism refers to

of

whom ^

The

secondary

interpretation of the impHcative form '/ implies q' as is

developed in Chapter

III, § 9,

where the modal adjectives

necessary, possible, impossible, are introduced.

INTRODUCTION

xviii

as useless on the

ground that

involve petitio principii.

all

He

such forms of inference

then proceeds:

believe

'I

both these opinions to be fundamentally erroneous,' and this would seem to imply that he proposed to relieve the syllogism from the charge.

I

believe, however, that

—

all logicians who have referred to Mill's theory group which includes almost everyone who has written on the subject since his time have assumed that the purport of the chapter was to maintain the charge of petitio principii, an interpretation which his opening reference to previous logicians would certainly not seem to bear. His subsequent discussion of the subject is, verbally at least, undoubtedly confusing, if not self-contradictory; but my personal attitude is that, whatever may have been Mill's general purpose, it is from his own

—

exposition that

I,

in

common

with almost

his con-

all

temporaries, have been led to discover the principle

according to which the syllogism can be relieved from the incubus to which In

of Aristotle.

my

it

had been subject since the time

view, therefore, Mill's account of

the philosophical character of the syllogism trovertible

;

I

would only ask readers

is

incon-

to disregard

from

the outset any passage in his chapter in which he

appears to be contending for the annihilation of the syllogism as expressive of any actual Briefly his position

may be

mode

of inference.

thus epitomised.

Taking

a typical syllogism with the familiar major 'All

men

are mortal,' he substituted for 'Socrates' or 'Plato' the

minor term 'the Duke of Wellington' who was then living. He then maintained that, going behind the syllogism, certain instantial evidence

tablishing the major;

is

required for es-

and furthermore that the

validity

INTRODUCTION of the conclusion that the

Duke

of

xix

WelHngton would

die depends ultimately on this instantial evidence. interpolation of the universal major

'

All

men

The

will die

has undoubted value, to which Mill on the whole did justice; but he pointed out that the formulation of this

universal adds nothing to the positive or factual data

upon which the conclusion depends. It follows from his exposition that a syllogism whose major is admittedly established by induction from instances can be relieved from the reproach of begging the question or circularity if, and only if, the minor term is not included in the

The Duke of Wellington being have formed part of the evidence upon which the universal major depended. It was thereultimate evidential data. still

living could not

fore part of Mill's logical standpoint to maintain that

there were principles of induction by which, from a limited

number

of instances, a universal going

these could be logically justified.

beyond

This contention may

be said to confer constitutive validity upon the inductive process.

It is directly

associated with the further con-

sideration that an instance, not previously examined,

may

be adduced to serve as minor premiss for a syllogism,

and

that such an instance will always preclude circularity

in the formal process.

Now the

charge of circularity or

is epistemic; and the whole of Mill's argument may therefore be summed up in the statement that the epistemic validity of syllogism and the constitutive validity of induction, both of which had been disputed by earlier logicians, stand or fall together.

petitio principii

In order to prevent misapprehension in regard to Mill's

view of the syllogism,

it

must be pointed out that

he virtually limited the topic of his chapter to cases

in

INTRODUCTION

XX

which the major premiss would be admitted by all logicians to have been established by means of induction in the ordinary sense, i.e. by the simple enumeration of instances; although many of them would have contended that such instantial evidence was not by itself sufficient. Thus all those cases in which the major was otherwise established, such as those based on authority, intuition or demonstration, do not

Unfortunately

solution.

have confused

his

fall

all

within the scope of Mill's the commentators of Mill

view that universals cannot be

in-

tuitively but only empirically established, with his specific is

contention in Chapter IV.

I

admit that he himself

largely responsible for this confusion,

and

therefore,

while supporting his view on the functions of the syllogism,

I

must deliberately express

my

opposition to

his doctrine that universals can only ultimately

be estab-

and limit my defence to his analysis of those syllogisms in which it is acknowledged that the major is thus established. Even here his doctrine that all inference is from particulars to particulars is open to lished empirically,

fundamental criticism

;

my

and, in

treatment of the

principles of inductive inference which will be developed in Part III,

shall substitute

I

an analysis which

will

take account of such objections as have been rightly

urged against

Mill's exposition.

[Note. There are two cases

employed

in Part II differs

in

from that

which the technical terminology in Part I.

Part

Part

11, logically as

equivalent to axiom.

Part

I,

I,

is

applies to the form of a

a principle of inference.]

(i)

The

phrase /nW-

to be understood psychologically; in

tive proposition, in

compound

(2)

Counter-impiicative, in

proposition; in Part II, to

CHAPTER

I

INFERENCE IN GENERAL Inference

§ I.

is

a mental process which, as such,

has to be contrasted with impHcation.

The

connection

between the mental act of inference and the relation is analogous to that between assertion and

of implication

the proposition. Just as a proposition tially assertible,

two propositions bility

is

what

is

poten-

so the relation of implication between is

an essential condition for the possi-

of inferring one from the other; and, as

it

is

impossible to define a proposition ultimately except in

terms of the notion of asserting, so the relation of implication can only be defined

in

terms of inference.

This consideration explains the importance which

I

attach to the recognition of the mental attitude involved in inference

and assertion afterwhich the ;

strictly logical

question as to the distinction between valid and invalid inference can be discussed.

To distinguish

the formula

of implication from that of inference, the former

may

be symbolised *If/ then q^ and the latter 'p therefore q,' where the symbol q stands for the conclusion and^ for the

premiss or conjunction of premisses.

The ference

proposition or propositions from which an inis

made being

position inferred being

commonly supposed

called premisses,

called

the

and the pro-

conclusion,

it

first presented in thought, and that the transifrom these to the thought of the conclusion is the

positions tion J.

is

that the premisses are the pro-

L. II

I

CHAPTER

2

step in the process.

last

usually the case

;

that

is

But

I

fact the reverse

in

to say,

we

first

is

entertain in

thought the proposition that is technically called the conclusion, and then proceed to seek for other propositions which would justify us in asserting

conclusion may, on the one hand,

first

it.

present

The

itself to

us as potentially assertible, in which case the mental

process of inference consists in transforming what was potentially assertible into a proposition actually asserted.

On

we may have already

the other hand,

satisfied

ourselves that the conclusion can be validly asserted apart from the particular inferential process, in which

case

we may

yet seek for other propositions which,

functioning as premisses, would give an independent or additional justification for our original assertion.

In

every case, the process of inference involves three distinct assertions

tion q.'

oV ql and It

:

first

the assertion of

*/,'

next the asser-

would imply would imply q^ which is

thirdly the assertion that ^p

must be noted that

'/

the proper equivalent of 'if/ then

^,' is

the

more

correct

expression for the relation of implication, and not 'p

—

which rather expresses the completed inThis shows that inference cannot be defined in terms of implication, but that implication must be defined in terms of inference, namely as equivalent to potential inference. Thus, in inferring, we are not

implies q' ference.

merely passing from the assertion of the premiss to the assertion of the conclusion, but

we

are also implicitly

asserting that the assertion of the premiss

is

used to

justify the assertion of the conclusion. § 2.

Some

importance

in

difficult

problems, which are of special

psychology, arise

in

determining quite

INFERENCE IN GENERAL

3

precisely the range of those mental processes which

may be

called inference: in particular,

tion or inference

is

involved

in

how

far asser-

the processes of asso-

and of perception. These difficulties have been aggravated rather than removed by the quite false antithesis which some logicians have drawn between logical and psychological inference. Every inference is a mental process, and therefore a proper topic for psychological analysis on the other hand, to infer is to think, and to think is virtually to adopt a logical attitude; for everyone who infers, who asserts, who thinks, intends to assert truly and to infer validly, and this is what conciation

;

stitutes assertion or inference into a logical process. is

It

the concern of the science of logic, as contrasted with

psychology, to

criticise

such assertions and inferences

from the point of view of their validity or invalidity. Let us then consider certain mental processes particular processes

of association

— which

—

in

have the

semblance of inference. In the many unmistakeable cases of association in which no inference whatever is even apparently involved. Any first

place, there are

familiar illustration, either of contiguity or of similarity, will

prove that association in itself does not entail inIf a cloudy sky raises memory-images of a

ference.

storm, or leads to the mental rehearsal of a poem, or

suggests the appearance of a slate roof, in none of these revivals

by association

is

there involved anything in the

remotest degree resembling inference. that which

tiguity

is

involve

some sort

is

is

The case

of con-

most commonly supposed

to

of inference; but in this supposal there

a confusion between recollection and expectation.

Our

recollection of storms that

we have experienced

in

CHAPTER

4 the past

a storm

is is

I

obviously distinct from our expectation that

coming on

in the

immediate

this latter process of expectation,

future.

and not

or less properly applied

;

but even here

We

we

storm when at in

to

to the former

process of recollection, that the term inference a careful psychological distinction.

It is

more

is

we must make may expect a

notice the darkness of the sky, without

having actually recalled past experiences of storms; this case no inference is involved, since there has

all

been only one

what would constitute the conclusion without any other assertion that would assertion, namely,

In order to speak properly of

constitute a premiss.

inference in such cases, the assertion that the sky will

be a storm.

is

minimum

required

is

the

cloudy and that therefore there

Here we have two

explicit assertions,

together with the inference involved in the word 'therefore.'

It is

of course a subtle question for introspection

as to whether this threefold assertion really takes place.

This

difficulty

inference;

it

does not at

would only

all affect

our definition of

affect the question

whether

in

any given case inference had actually occurred. It has been suggested that, where there has been nothing that logic could recognise as an inference, there has yet been inference in a psychological sense; but this contention is absurd, since it is entirely upon psychological grounds that we have denied the existence of inference in

such cases.

Let us consider further the logical aspects of a genuine inference, following upon such a process of association as

we have

illustrated.

The

hold that the appearance of the sky

is

scientist

may

not such as to

warrant the expectation of an on-coming storm.

He

INFERENCE IN GENERAL

5

may, therefore, criticise the inference as invalid. Thus, assuming the actuaHty of the inference from the psychological point of view, it may yet be criticised as invalid from the logical point of view. So far we have taken the simplest case, where the single premiss 'The sky is

cloudy'

is

But,

asserted.

when an

additional premiss

such as 'In the past cloudy skies have been followed

by storm'

is

then the inference

asserted,

further

is

two premisses taken together more complete ground for the conclusion

rationalised, since the

constitute a

This additional premiss

than the single premiss. technically

thinker

is

known

as

2.

particular proposition.

pressed to find

for his conclusion,

he

assert that in all his expe-

riences cloudy skies have been followed limited universal).

The

final

by storm

stage of rationalisation

reached when the universal limited to cases

If the

stronger logical warrant

still

may

is

all

(a is

remembered

used as the ground for asserting the unlimited

is

But even now the critic may press for further justification. To pursue this topic would obviously require a complete treatment of induction, syllogism, etc., from the logical point of view. Enough has been said to show that, however inadequate may be the grounds offered in justification of a conclusion, this has no bearing upon the nature or upon universal for

all

cases.

the fact of inference as such, but only upon the criticism of

it

as valid or invalid.

As logical

in association, so also in perception, a

problem presents

itself.

There appear

psychoto

be at

least three questions in dispute regarding the nature of

perception, which have close connection with logical analysis: First,

how much

is

contained

in the

percept

CHAPTER

6

I

besides the immediate sense experience?

does perception involve assertion? involve inference?

problem,

let

To

illustrate the

us consider what

perception of a match-box.

is

This

Secondly,

does

Thirdly,

nature of the

meant by the is

it

first

visual

generally supposed

to include the representation of its tactual qualities

which case, the content of the percept includes

;

in

qualities

other than those sensationally experienced.

On

the

other hand, supposing that an object touched in the

dark

is

recognised as a match-box, through the special

character of the tactual sensations, would the represen-

match-box from other objects be included in the tactual perception of it as a match-box ? The same problem arises when we recognise a rumbling noise as indicating a cart in

tation of such visual qualities as distinguish a

the road:

i.e.

should

we

say,

in

this case, that the

auditory percept of the cart includes visual or other distinguishing characteristics of the cart not sensationally

experienced? In

my view it is

inconsistent to include in

the content of the visual percept tactual qualities not sensationally experienced, unless

we

also include in the

content of a tactual or auditory percept visual or similar qualities not sensationally experienced

in

This leads up to our second question, namely whether such perceptions there is an assertion {a) predicating

of the experienced sensation certain specific qualities; or an assertion {B) of having experienced in the past similar sensations simultaneously with the perception of ^

In speaking here of the mental representation of qualities not

sensationally experienced, I

portant psychological

am

putting entirely aside the very im-

question as to whether such mental repre-

sentations are in the form of 'sense-imagery' or of 'ideas.'

INFERENCE IN GENERAL a certain object.

we may

first

7

Employing our previous

illustration,

question whether the assertion 'There

is

a cart in the road' following upon a particular auditory sensation,

involves

of that sensation.

the

(a)

Now

if

explicit

characterisation

the specific character of the

noise as a sensation merely caused 2. visual image which in its turn

caused the assertion 'There

road,' then in the explicit inference.

is

absence of assertion In order to

a cart in the

{a) there is

become

no

inference, the

character operating (through association) as cause would

have to be predicated (in a connective judgment) as ground. On the other hand, any experience that could be described as hearing a noise of a certain more or less determinate character would involve,

in

my

opinion,

besides assimilation, a judgment or assertion {a) expres-

some such words

sible in

The is

as 'There

further assertion that there

is

is

a rumbling noise.'

a cart in the road

accounted for (through association) by previous ex-

periences of hearing such a noise simultaneously with

Assuming that association operates by arousing memory-images of these previous experiences, it is only when by their vividness or obtrusiveness these memory-images give rise to a memory -judgment, that the assertion (^) occurs. We are now in a position to seeing a

cart.

answer the third question as for, if

to the nature of perception

either the assertion of [a) alone or of {b) with (a)

occurs along with the assertion that there the road, then inference

is

is

involved; otherwise

a cart in it is

not.

Passing from the psychological to the strictly logical problem, we have to considei; in further detail § 3.

the conditions for the validity of an inference symbolised as 'p

.'

.

qJ

These conditions are

twofold,

and may be

CHAPTER

8

conveniently distinguished

in

I

accordance with

nology as constitutive and epistemic.

my termi-

They may be

briefly formulated as follows:

Conditions for Validity of the Inference 'p

(ii)

.'.

q'

Constitutive Conditions: (i) the proposition '/' and the proposition 'p would imply q^ must both be true. Epistemic Conditions: (i) the asserting of '/' and

(ii) the asserting of '/ would imply q' must both be permissible without reference to the asserting of q.

be noted that the constitutive condition exthe dependence of inferential validity upon a

It will

hibits

between the contents of premiss and of conclusion the epistemic condition, upon a certain relation between the asserting of the premiss and the asserting of the conclusion. Taking the constitutive condition first, we observe that the distinction between inference and implication is sometimes expressed by certain relation ;

calling implication 'hypothetical inference'

ing of which

is that,

must be categorically asserted implication, this premiss thetically.

— the mean-

in the act of inference, the

is

;

premiss

while, in the relation of

put forward merely hypo-

This was anticipated above by rendering

the relation of implication in the subjunctive

mood

(/ would imply ^) and the relation of inference

in the

indicative

mood

[p implies q\

Further to bring out the connection between the epistemic and the constitutive conditions,

it

must be

pointed out that an odd confusion attaches to the use of the word 'imply' in these problems. The almost universal application of the relation of implication in logic

is

as a relation

between two propositions; but, in term 'imply' is used as a relation

familiar language, the

INFERENCE IN GENERAL between two

9

Consider for instance

assertions.

(a) 'B's

asserting that there will be a thunderstorm would imply

having noticed the closeness of the atmosphere,' and (S) 'the closeness of the atmosphere would imply that there will be a thunderstorm.' The first of these relates his

two mental acts of the general nature of assertion, and is an instance of 'the asserting of ^ would imply having asserted/'; the second is a relation between two propositions, and is an instance of 'the proposition/ would imply the proposition ^.' Comparing (a) with (d) we find that implicans and implicate have changed places. Indeed the sole reason why the asserting of the thunderstorm was supposed to imply having asserted the closeness of the atmosphere was that, in the speaker's judgment, the closeness of the atmosphere would imply that there will be a thunderstorm.

Recognising, then, this double and sometimes am-

biguous use of the word 'imply,'

we may

restate the

of the two epistemic conditions and the second of

first

the two constitutive conditions for the validity of the inference

'/>

.'.

q' as follows:

Epistemic condition sition '/' should not

proposition

(i)

Constitutive condition

former

the asserting of the propo-

'^.'

imply the proposition

The

:

have implied the asserting of the

is

(ii)

:

the proposition '/' should

'^.'

merely a condensed equivalent of our

original formulation, viz. that 'the asserting of the pro-

position

'/'

must be permissible without reference

asserting of the proposition

Now

to

the

'q.'

the fact that there

is

this

double use of the

term 'imply' accounts for the paradox long

felt

as

CHAPTER

10

regards the nature of inference

I

:

for

may be

order that an inference

it is

urged

that, in

formally valid,

it

is

required that the conclusion should be contained in the

premiss or premisses; while, on the other hand,

if

there

any genuine advance in thought, the conclusion must not be contained in the premiss. This word 'contained' is doubly ambiguous: for, in order to secure formal validity, the premisses regarded as propositions must is

imply the conclusion regarded as a proposition

;

but, in

order that there shall be some real advance and not a

mere

petitio principii,

it is

required that the asserting

of the premisses should not have implied the previous

These two horns of the dilemma are exactly expressed in the constitutive and asserting of the conclusion.

epistemic conditions above formulated. § 4.

We

shall

now

explain

how

the constitutive

conditions for the validity of inference, which have been

expressed

most general form, are realised

in their

familiar cases.

would imply

The

in

general constitutive condition 'p

q' is yi?r?;^^//)/ satisfied

logical relation holds of

/

to

q-,

when some

and

it

is

specific

upon such a

relation that the formal truth of the assertion that 'p

would imply q' relations which

is

based.

will

There are two fundamental

render the inference from

/

to q,

and these relations will be expressed in formulae exhibiting what will be called the Applicative and the Implicative Principles of Inference. The former may be said to formulate what is involved in the intelligent use of the word 'every'; the latter what is involved in the intelligent use of the word 'if.' not only valid, but formally valid

;

In formulating the Applicative principle,

we

take

p

INFERENCE IN GENERAL

ii

to stand for a proposition universal in form,

and q

for

a singular proposition which predicates of

some

single

case what

The

Appli-

predicated universally in p.

is

cative principle will then be formulated as follows:

a predication about 'every'

we may

same predication about 'any

given.'

From infer the

In formulating the Implicative principle,

compound

to stand for a ''x implies

'y'

The

and q

J)/'"

formally

we take/

proposition of the form 'x and

to stand for the simple proposition

Implicative principle will then be formulated

as follows:

y

From the compound proposition we may formally infer

'x

and

''x implies

'jj/.'

We find two different forms of proposition,

§ 5.

or other of which inference;

the

is

used as a premiss

distinction

logicians.

is

funda-

controversy

In familiar logic the two kinds of

proposition to which tively as universal

much

one

every formal

between which

mental, but has been a matter of

among

in

I

known respecAs an example of

shall refer are

and hypothetical.

the former, take 'Every proposition can be subjected

from this universal proposition we 'That ''matter exists'' can be submay directly infer jected to logical criticism.' This inference illustrates to logical criticism';

what

have

I

premiss

will

called the Applicative Principle,

be called an Applicational universal.

next the example 'If this can swim

it

breathes,'

and and

can swim'; from this conjunction of propositions

'it

we

breathes'; here, the hypothetical premiss

infer that

'it

being

our terminology called implicative, the

in

its

Take

in-

ference in question illustrates the use of the Implica-

CHAPTER

12

tive Principle.

ciples that

It is

I

the combination of these two prin-

marks the advance made

in

passing from

the most elementary forms of inference to the syllogism.

For example: swim' we can

From 'Everything

breathes

infer 'This breathes

where the applicative principle only

is

if

if

able to

able to swim,'

employed. Con-

joining the conclusion thus obtained with the further

premiss 'This can swim,'

we can

infer 'this breathes,'

where the implicative principle only is employed. In which involves the interpolation of an additional proposition, we have shown how the two principles of inference are successively this analysis of the syllogism

employed.

The

would read as

ordinary formulation of the syllogism follows:

'Everything that can swim

breathes; this can swim; therefore this breathes.' place of the usual expression of the major premiss,

In I

have substituted 'Everything breathes if able to swim,' in order to show how the major premiss prepares the

way

for the inferential

employment successively of the

and of the implicative principles. the two propositions Every proposition can be subjected to logical criticism' and 'everything that is able to swim breathes' must be carefully contrasted. Both of them are universal in form; but in the

applicative § 6.

Now

latter the subject

'

term contains an

explicit characterising

The

presence of a charac-

adjective, viz. able to swim.

terising adjective in the subject anticipates the occasion

on which the question would arise whether this adjecIn the tive is to be predicated of a given object. syllogism, completed as in the preceding section, the universal major premiss is combined with an affirmative

minor premiss, where the adjective entertained

cate-

INFERENCE IN GENERAL gorically

2.?,

predicate of the minor

is

13

same

the

as that

which was entertained hypothetically as subject of the major. This double functioning of an adjective is the one fundamental characteristic of all syllogism where it will be found that one (or, in the fourth figure, every) term occurs once in the subject of a proposition, where ;

it

is

entertained hypothetically, and again in the pre-

dicate of another proposition

where

is

it

entertained

categorically.

The

between the two contrasted universals (applicational and implicational) lies in the fact that an inference can be drawn from the former on the applicative principle alone, which dispenses with the minor premiss. We have to note the nature of the essential distinction

substantive that occurs in the applicational universal as distinguished from that which occurs in the implicational universal.

position

'

The example

already given contained 'pro-

as the subject term,

and a few other examples

are necessary to establish the distinction in question.

'Every individual of the Republic of predications

is

is self-identical,'

therefore 'the author

self-identical';

'Every conjunction

is

commutative,' therefore 'the conjunc-

tion lightning before '

Every

adjective

is

and thunder after

is

commutative'

a relatively determinate specifica-

tion of a relatively indeterminate adjective,' therefore

'red

is

tively

a relatively determinate specification of a relaindeterminate

adjective.'

These

could be endlessly multiplied, in which

illustrations

we

directly

apply a universal proposition to a certain given instance. In such cases the implicative as well as the applicative principle

would have been involved

if

it

had been

necessary or possible to interpolate, as an additional

CHAPTER

14

I

datum, a categorical proposition requiring certification, to serve as minor premiss. Let us turn to our original

and examine what would have been involved if we had treated the inference as a syllogism; it would have read as follows: 'Every proposition can be subjected to logical criticism'; 'That matter exists is a proposition'; therefore 'That matter exists can be subillustration

jected to logical criticism.'

word proposition occurs premiss, and as predicate I

have to maintain

premiss

is

In this form, the substantive as subject

the universal

in

minor

that this introduction of a

is

superfluous and even misleading.

be observed

What

in the singular premiss.

that, in all the illustrations

It

should

given above of

the purely applicative principle, the subject-term in the universal premiss denotes a general category.

It

follows

from this that the proposed statement 'That matter exists is

is

a proposition

'

is

redundant as a premiss

for

it

impossible for us to understand the meaning of the

phrase 'matter exists' except so far as it

;

to denote a proposition.

In the

we understand

same way,

would

it

be impossible to understand the word 'red' without understanding it to denote an adjective and so in all other cases of the pure employment of the applicative principle. In all these cases, the minor premiss which ;

—

might be constructed is not a genuine proposition the truth of which could come up for consideration because the understanding of the subject-term of the minor demands a reference of it to the general category there predicated of it. This proposed minor premiss, therefore, is a peculiar kind of proposition which is not exactly what Mill calls 'verbal,' but rather what

meant by

'analytic,'

and which

I

propose to

call

'

Kant struc-

INFERENCE IN GENERAL

All structural statements contain as their pre-

tural.'

dicate

15

some wide logical

category, and their fundamental

impossible

to realise the

meaning of the subject-term without

implicitly con-

characteristic

is

that

it

is

under that category. The structural proposition can hardly be called verbal, because it does not depend upon any arbitrary assignment of meaning to ceiving

it

a word;

—

examples.

this point

For

being best illustrated by giving

instance, taking as subject-term

'the

'The author of the Republic wrote something,' would be verbal, while The author of the Republic is an individual,' would

author of the Republic,' then

'

be

structural.

In reality the subject of a verbal pro-

and the subject of a structural proposition are not the same; the one has for its subject the phrase 'the author of the Republic,' and the other the object denoted by the phrase. This is the true and final principle for position,

distinguishing a structural (as well as a genuinely real

or synthetic statement) from a verbal statement. § 7.

Since a category

expressed always by a

is

general substantive name, the important question arises as to whether or

how

the

'existent' or 'proposition'

name is

ordinary general substantive

to

of a category such as

name

is

be

but, so far as a category can

;

in

the

defined in terms

of determinate adjectives which constitute tion

Now

be defined.

connota-

its

be defined,

terms of adjectival determinables\

e.g.

it

ihust

an existent

what occupies some region of space or period of time the determinates corresponding to which would be, occupying some specific region of space or period of is

:

time.

Similarly,

the category

'proposition'

could be

defined by the adjectival determinable 'that to which

CHAPTER

i6

some

I

assertive attitude can be adopted,' under

which

the relative determinates would be affirmed, denied, doubted, etc.

We

may

indicate the nature of a given

category by assigning the determinables involved construction.

Using

in its

capital letters for determinables

and corresponding small letters for their determinates (distinguished amongst themselves by dashes), the major premiss of the syllogism would assume the following form Every \s p \{ m; where the determinables and serve to define the category so far as required

M

MP

:

P

for the syllogism in question.

the vague

word

Here we

'thing' previously

substitute for

employed, the symbol

MP to indicate the category of reference

;

namely, that

comprising substantives of which some determinate character under the determinables dicated.

The

Til/

and P can be pre-

statement that the given thing

redundant where

M and P

is

MP

is

are determinables to which

the given thing belongs for the thing could not be given ;

an act of construction except so far as it was given under the category defined by these determinables. Hence any genuine act of characterisation of the thing so given would consist in giving to either immediately or in

these mere determinables a comparatively determinate

For example,

value.

thing

is

it

MP, we may

being assumed that the given characterise

it

in

such determi-

nate forms as 'm and/*,' 'm or/,' 'p \i m,' 'not both/> and m' where the predication of the relative determinates m and / would presuppose that the object had been constructed under MP. In defining the function of a proposition to be to characterise relatively determinately what is given to be characterised, we now see that what is 'given is not given in a merely abstract

INFERENCE IN GENERAL sense, but

—

in

being given

17

—the determinables which

have to be determined are already presupposed. § 8.

We

may now show more

clearly

why

the force

from that of the term if and how, in the syllogism, the two corresponding principles of inference are both involved. The major

of the term 'every'

distinct

is

*

;

premiss having been formulated

minables

M and P,

in

terms of the deter-

the whole argument will assume

the following form

Every

{a)

from which we

MP is/ infer,

The given

[b)

m,

if

by the applicative principle alone is/ if m.

MP

Next we introduce the minor,

The given

{c)

and

finally infer,

{d)

Now

if

MP

viz.

is m,,

by the implicative principle alone:

The given MP'isp. we held that the inference from

{a) to {b) re-

quired the implicative principle as well as the applicative,

'The given thing is MP' the syllogism would assume the

so that a minor premiss

must be interpolated, following [a)

more complicated form:

Everything

is

/

\{

m

if

is

/

MP (the

reformulated

major). .'.

{b)

The

given thing

if

;^

if

MP

(by the

applicative principle alone).

Next we introduce {c) .'.

{d)

The The

as minor

given thing given thing

is is

MP. / if w

(by the implicative

principle alone); finally, (e) .'.

(/)

introducing the original minor,

The given The given

thing thing

is is

viz.

m.

/

(by the implicative prin-

ciple alone). J. L. II

2

CHAPTER

i8

Now

this

I

lengthened analysis of the syllogism, while

involving the implicative principle twice, involves as well as the applicative principle the introduction of a

new

MP,

which hints at the doubt whether what is given is given as MP. But if this were a reasonable matter of doubt requiring explicit affirmation, on the same principle we might doubt whether what is given is a 'thing,' in some more minor, viz, that the given thing

generic sense of the word 'thing.' mitted, the syllogism

is

is

If this

doubt be ad-

resolved into three uses of the

implicative principle, with two extra minor premisses.

Such a resolution would in fact lead by an infinite regress to an infinite number of employments of the implicative principle. To avoid the infinite regress we must establish some principle for determining the point at which an additional minor is not required. The view then that I hold is not merely that what is given is a 'thing' in the widest sense of the term thing, but that

what

is

given

is

always given as demanding to be

characterised in certain definite respects size,

—

e.g. colour,

MP'

—

and that 'The given thing is

weight; or cognition, feeling, conation

therefore such a proposition as

presupposed in its being given, i.e. in being given as requiring determination with respect and P. The above to these definite determinables syllogism which the is resolved formulation, therefore, in is

given,

it is

M

into a process involving the applicative

cative principles each only once, for

it

is

and the impli-

logically justified;

brings out the distinction between the function of

employment of the and the function of if as

the term every as leading to the applicative principle alone,

leading to the employment of the implicative principle

INFERENCE IN GENERAL

19

and furthermore it distinguishes between the process in inference which requires the applicative principle alone from that which requires the implicative as alone;

well as the applicative principle.

The

between the cases

distinction

in

which the im-

or cannot be dispensed with whether depends, so upon the subject-term of the universal stands for a logical category or not. But we may go further and say that, even if the subject of the plicative principle can far,

universal

is

not a logical category, provided that

it

is

definable by certain determinates, and that the subject

of the conclusion

is

only apprehensible under those

determinables, then again the use of the implicative principle

may be

For example:

dispensed with.

'All

material bodies attract; therefore, the earth attracts.'

Here the term

'material body'

category in that

it

is

of the nature of a

can only be defined under such de-

terminables as 'continuing to exist' and 'occupying some region of space'

;

furthermore the earth

is

constructively

given under these determinables: hence a proposed

minor premiss to the

body

is

superfluous,

effect that the earth is

a material

and the above inference involves

only the applicative principle. Again 'All volitional acts are causally determined; therefore, Socrates' drinking

of hemlock was causally determined.'

of the conclusion

is

Here the

subject

constructively given under the de-

terminables involved in the definition of volitional

which again alone.

gate

is

justifies the

use of the applicative principle

As a third example less

act,

' :

Every denumerable aggre-

than some other aggregate: therefore, an

aggregate whose number

is

5resup/>oses it, in same way as a proposition presupposes the understanding of the meaning of the terms involved identity,

just the

without asserting such meaning. 8

10.

We

have discussed the case

in

which a minor

INFERENCE IN GENERAL

21

may be dispensed with, namely that in which a certain mode of using the applicative principle is premiss

without the employment of the implicative.

sufficient

We

now

will

turn to a complementary discussion of the

case in which there

is

unnecessary employment of the

by the insertion of what may be called a redundant major premiss. It will be convenient to call the redundant minor premiss a subminor, and the redundant major premiss to which we applicative principle, entailed

shall

now

turn

—a

—

super-major.

In this connection

I

shall introduce the notion of a formal principle of in-

ference,

which

will apply, not

strictly formal,

only to inferences that are

but also to inferences of an inductive

nature, for which the principle has not at present been finally

formulated and must therefore be here expressed

without qualifying

detail.

The

discussion will deal with

cases in which the relation of premiss or premisses to

conclusion

is

such that the inference exhibits a formal

principle.

We

the point first by taking the and next, the ultimate (but as yet

shall illustrate

principle of syllogism,

unformulated) principle of induction. syllogism, taking

/

and q

As

to represent

regards the

the premisses

and r the conclusion, we may say that the

syllogistic

principle asserts that provided a certain relation holds

between the three propositions p, q, and r, inference from the premisses p and q alone will formally justify the conclusion r. Now it might be supposed that this syllogistic principle constitutes in a sense an additional premiss which, when joined with p and q, will yield a more complete analysis of the syllogistic procedure. But on consideration it will be seen that there is a sort

CHAPTER

22

I

of contradiction in taking this view: for the syllogistic principle asserts that the premisses

/

and q are alone

sufficient for the formal validity of the inference, so that, if

the principle

is

inserted as an additional premiss co-

ordinate with

/

contradicted.

In illustration

and

q,

the principle itself

we

will

is

virtually

formulate the syllo-

gistic principle:

to

'What can be predicated of every member of a class, which a given object is known to belong, can be pre-

dicated of that object.'

Now, taking a

specific syllogism:

'Every labiate .'.

if

we

The The

is

dead-nettle dead-nettle

square-stalked, a labiate, is square-stalked,'

is

inserted the above-formulated principle as a pre-

miss, co-ordinate with the

two given premisses, with a

view to strengthening the validity of the conclusion, this would entail a contradiction because the principle ;

claims that the two premisses are alone sufficient to justify the conclusion

Now

the

same

'The dead-nettle

is

square-stalked.'

holds, mutatis mutandis, of

any pro-

posed ultimate inductive principle. Here the premisses but as many, and summed up not as two

are counted in

—

—

the single proposition 'All examined instances charac-

by a certain adjective are characterised by a certain other adjective'; and the conclusion asserted terised

(with a higher or lower degree of probability) predicates of all

what was predicated

all exam,ined.

Now, in accordance with the inductive summary premiss is sufficient for asserting

principle, the

in

the premiss of

the unlimited universal (with a higher or lower degree

of probability).

To

insert this principle, as

an additional

INFERENCE IN GENERAL

23

premiss co-ordinate with the summary premiss, would, therefore, virtually involve a contradiction. tion,

we

will

In illustra-

roughly formulate the inductive principle

'What can be predicated of all examined members of a class can be predicated, with a higher or lower degree of probability, of all members of the class.'

Now, taking a

specific inductive inference:

'All examined swans are white. .'. With a hig-her or lower degree of probability, all swans are white,' if

we

inserted the above-formulated inductive principle

as a premiss, co-ordinate with the

summary premiss

examined swans are

view to strengthening

white,' with a

'All

the validity of the conclusion, this would entail a contradiction

premiss

because the principle claims thatthis summary

;

alone

is

sufificient to justify

the conclusion that

'With a higher or lower degree of probability,

all

swans

are white.'

We

may

principle

shortly express the distinction between a and a premiss by saying that we draw the

conclusion

from

the premisses in accordance with (or

through) the principle.

In other words,

we immediately

see that the relation amongst the premisses and conclusion

is

principle,

a specific case of the relation expressed in the

and hence the function of the

principle

is

stand as a universal to the specific inference as an stance of that universal to

:

where the

be inferred from the former

(if

latter

there

is

may be

to in-

said

any genuine

Supreme Applicative from x =y and y = z, we may

inference) in accordance with the principle. infer

x = z.

For example

:

This form of inference

is

expressed, in

general terms, in the Principle: 'Things that are equal to the

same thing are equal

to

one another.' Now, here,

CHAPTER

24

x^y 2indy = 2—are alone

the two premisses for the conclusion

/rom

I

x = 2;

sufficient

the conclusion being

drawn

the two premisses through or in accordance with

the principle which states that the two premisses are

a/one sufficient to secure validity for the conclusion.

The

principle cannot therefore be

added co-ordinately Moreover the

to the premisses without contradiction.

above-formulated principle (which expresses the transitive

property of the relation of equality) cannot be

subsumed under the

way

syllogistic principle.

In the

same

the syllogistic or inductive principle

may be

called

a redundant or super-major, because

it

introduces a mis-

leading or dispensable employment of the applicative principle. § II.

There

is

a special purpose in taking the in-

ductive and syllogistic principles in illustration of super-

many

have maintained that any does not rest on an independent principle, but upon the syllogistic principle itself; in other words, they have taken syllogism to exhibit the sole form of valid inference, to which any majors, for

logicians

specific inductive inference

other inferential processes are subordinate.

Now

it

is

true that the inductive principle could be put at the

head of any

specific inductive inference,

and thus be

related to the specific conclusion as the major premiss

of a syllogism

is

related to

its

conclusion

could be said of the syllogistic principle

:

;

but the same

namely that

it

could be put at the head of any specific syllogistic inference to which

it

is

related in the

major premiss of a syllogism But,

if

we

is

same way

related to

its

as the

conclusion.

are further to justify the specific inductive

inference by introducing the inductive principle, then,

INFERENCE IN GENERAL by

parity of reasoning,

we should have

25

to introduce the

syllogistic principle further to justify the specific syllogistic inference.

would lead tration

will

But

in the case of the

syllogism this

to an infinite regress as the following illus-

show.

Thus, taking again as a specific

syllogism, that

from (/) 'All labiates are square-stalked'

and

we may

(^)

infer (r)

adding to principle, namely and,

'The dead-nettle 'The dead-nettle this

as

is is

a labiate' square-stalked,'

super-major the syllogistic

(a), we have the following argument For every case o( Af, of 6" and ofP: the inference 'every Jkf is P, and kS" is Af, .-. S is P' is valid. (d) The above specific syllogism is a case of (a).

(a)

(c)

.'.

The

specific syllogism

is

valid.

But here, in inferring from (a) and (d) together to (c), we are employing the syllogistic principle, which must stand therefore as a super-major to the inference from (a) and (d) together to (c), and therefore as super-supermajor to the specific inference from/ and ^ to r. This would obviously lead to an infinite regress. We may show that a similar infinite regress would be involved if we introduced, as super-major, the inductive principle, by the following illustration. Taking again as a specific inductive inference that from 'All examined swans are white' we may infer with a higher All swans are or lower degree of probability that white'; and adding to this as super-major the inductive principle, namely (a), we have the following '

arg-ument: (a) For every case of Af and of P: from 'e veryexamined Af Is P,' we may infer, with a higher or lower degree of probability, that 'every Af is P';

CHAPTER

26

I

The above specific induction is a case of (a), .'. The specific induction is valid. here we may argue in regard to this (a), (d), {c)

{b) (c)

But,

as

Thus, by introducing the inductive principle as a redundant major premiss, we shall be led as before, by an infinite regress, in the case of the

to a repeated

previous

employment

(a), (d),

(c).

of the syllogistic principle.

This whole discussion forces us to regard the inductive and syllogistic principles as independent of one another, the former not being capable of subordination to the latter; for

we cannot

in

any way deduce the

ductive principle from the syllogistic principle.

who have regarded

in-

Those

the syllogistic principle as ultimately

in fact arrived at this conclusion by noting shown above, the inductive principle could be introduced as a major for any specific inductive inference, in which case the inference would assume the syllogistic form {a\ (d), (c). But this in no way affects the supremacy

supreme, have that, as

of the inductive principle as independent of the syllogistic.

CHAPTER

II

THE RELATIONS OF SUB-ORDINATION AND CO-ORDINATION AMONGST PROPOSITIONS OF DIFFERENT TYPES § I.

In the previous chapter

we have shown

that the

syllogism which establishes material conclusions from material premisses involves the alternate use of the

Applicative and Implicative principles. principles, its

Now these

two

which control the procedure of deduction

in

widest application, are required not only for material

inferences, but also for the process of establishing the

formulae that constitute the body of logically certified theorems.

All these formulae are derived from certain

intuitively

evident axioms which

may be

explicitly

be found that the procedure of deducing further formulae from these axioms requires enumerated.

It

will

only the use of the Applicative and Implicative principles

;

these, therefore, cover a wider range than that

But a final question remains, as to how the formal axioms are themselves established in their universal form. By most formal logicians it is assumed that these axioms are presented immediately as self-evident in their absolutely universal form but such a process of intuition as is thereby assumed is really the result of a certain development of the reasoning of mere syllogism.

;

powers. is

Prior to such development,

I

hold that there

a species of induction involved in grasping axioms in

their absolute generality

and

in

conceiving of form as

CHAPTER

28

II

constant in the infinite multiplicity of cations.

We

its

possible appli-

therefore conclude that behind the axioms

there are involved certain supreme principles which bear to the Applicative

and Implicative principles the same

relation as induction in general bears to deduction

;

and,

even more precisely, that these two new principles may be regarded as inverse to the Applicative and Implicative principles respectively. This being so, it will be convenient to denominate them respectively. Counterapplicative andCounter-implicative. It should bepointed

out that whereas the Applicative and Implicative principles hold for material as well as formal

procedure,

Counter-principles

the

are

inferential

used for the

establishment of the primitive axioms themselves upon

which the formal system

is

based.

We

will

then pro-

ceed to formulate the Counter-principles, each in immediate connection with § 2.

The

its

corresponding direct principle.

Applicative principle

is

that which justifies

the procedure of passing from the asserting of a predication about

'

every

'

to the asserting of the

predication about 'any given.'

same

Corresponding to this, may be formulated:

the Counter-applicative principle

'When we are justified in passing from the asserting of a predication about some one given to the asserting of the same predication about some other, then we are also justified in asserting the same predication about every.

Roughly the Applicative from

justifies

principle justifies

inference

and the Counter-applicative inference from 'any' to 'every'; but whereas

'every'

to

'any,'

the former principle can be applied universally, the latter holds only in certain

narrowly limited cases; and.

SUB-ORDINATION AMONGST PROPOSITIONS in

particular,

for the

formulae of Logic. those in which

and

we

establishment of the primitive

These cases may be described as see the universal in the particular,

kind of inference

this

duction,' because

which we

29

it is

will

be called 'intuitive

in-

that species of generalisation in

intuite the truth of a universal proposition in

the very act of intuiting the truth of a single instanced

Since intuitive induction

is

of course not possible in

every case of generalisation,

we have

implied in our

formulation of the principle that the passing from 'any' to 'every'

is

justified only

one' to 'any other'

when

the passing from 'any

Now there

is justified.

are forms of

we can pass immediately from any one given case to any other if it were not so, the principle would be empty. For instance, we may illustrate the Applicative principle by taking the formula: 'For every value of/ and of ^, "/ and q' would imply "/",' from which we should infer that 'thunder and lightning' would imply 'thunder.' If now we enquire inference in which

;

how we oi

p

will

are justified in asserting that for every value

and of

q,

'p

and

q'

would imply

'/,'

the answer

supply an illustration of the Counter-applicative

principle.

Thus,

in asserting that

ning" would imply "thunder"'

'"thunder and light-

we

see that

we could

proceed to assert that '"blue and hard" would imply

and in the same act, that "/ and (7" would imply "/" for all values of/ and of ^.' The second inverse principle to be considered is § 3. "blue",'

'

Before discussing this inverse

the Counter-implicative. principle, ^

This

is

it

will

be necessary to examine closely the

a special case of

'

intuitive induction,' the

uses of which will be examined in Chapter VIII.

more general

CHAPTER

30

Implicative principle

formulated:

'Given

itself,

II

which may be provisionally

that a certain proposition

would

we can

validly

formally imply a certain other proposition,

latter from the former.' Now we one positive element in the notion of

proceed to infer the find that the

formal implication inference,

is its

equivalence to potentially valid

and that there

is

no single relation properly

called the relation of implication.

We

must therefore

bring out the precise significance of the Implicative

by the following reformulation: 'There are relations such that, when one or other of these subsists between two propositions, we may validly infer the one from the other.' From the principle

certain specifiable

enunciation of this principle

we can

to the enunciation of its inverse

pass immediately

— the Counter-implica-

tive principle

'When we have

inferred, with a consciousness of

some proposition from some given premiss or premisses, then we are in a position to realise the specific validity,

form of relation that subsists between premiss and conclusion upon which the felt validity of the inference depends.'

Here, as

in the case of the Counter-applicative principle,

we must

point out that there are cases in which

tuitively recognise the validity of inferring

we

in-

some con-

crete conclusion from a concrete premiss, before having

recognised the special type of relation of premiss to conclusion which renders the specific inference valid

otherwise the Counter-implicative principle would be

empty.

In illustration,

we will

trace back

some accepted

relation of premiss to conclusion, upon which the validity

of inferring the one from the other depends; and this

SUB-ORDINATION AMONGST PROPOSITIONS will entail reference to a preliminary

procedure

31

in ac-

cordance with the Counter-applicative principle;

for

every logical formula is implicitly universal. Thus we might infer, with a sense of validity from the information

'Some Mongols

are Europeans' and from this

alone, the conclusion

We

'Some Europeans

datum

are Mongols.'

proceed next in accordance with the Counter-appli-

cative principle to the generalisation that the inference

M

from 'Some

we

Finally

\s

P'

'Some

to

P

is

M'

is

always

valid.

are led, in accordance with the Counter-

implicative principle, to the conclusion that

it is

the re-

lation of 'converse particular affirmatives' that renders

the inference from

'Some

M

P'

is

to

'Some

P

is

M'

valid,

We

§ 4.

have regarded the

intuition underlying the

Counter-applicative principle as an instance of 'seeing

the universal in the particular'; and correspondingly the intuition underlying the Counter-implicative principle

may be regarded as an instance of 'abstracting a common But the dii'ect types of intuition operate over a much wider field than the Counter-applicative and Counter-implicative principles for, whereas form

in

diverse matter.'

:

the twin inverse principles operate only in the estab-

lishment

of

axioms,

the

form. plicitly

These

types

direct

are involved wherever there

is

of

intuition

either universality or

have been exstill more nature of the procedure conducted in

direct types of intuition

recognised by philosophers

purely intuitive

;

but the

accordance with the twin inverse principles accounts for the fact that these principles have hitherto not been

formulated by logicians.

Moreover the point of view

from which the inverse principles have been described

CHAPTER

32

and analysed

II

purely epistemic,

is

and the epistemic

aspect of logical problems has generally been ignored or explicitly rejected by logicians.

It

follows also from

their epistemic character that these principles, unlike

the Applicative and Implicative principles of inference,

cannot be formulated with the precision required for a purely mechanical or blind application. § 5. is

The

operation of these four supreme principles

best exhibited

by means of a scheme which comprises

propositions of every type in their relations of super-, or co-ordination to one another.

sub-,

We

propose,

therefore, to devote the remainder of this chapter to

the construction and elucidation of such a scheme. I.

Superordinate Principles of Inference. la. The Counter-applicative and Counter-implicative.

The

Id.

Applicative and Implicative.

Forrmdae:

i.e. formally certified propositions expressible in terms of variables having general

II.

application.

11^.

\\b.

III.

formulae (or axioms) derived from II I ^ in accordance with \a.

Primitive directly

Formulae successively derived from means of I b.

1 1

^ by

Formally Certified Propositions expressed in

terms having fixed application. \\\a. Those from which \\a are derived by use of the principles \a. \\\b.

Those which are derived from of the Applicative principle

I

V.

IId, (f>c, where (fya, x is not due to the nature of (^ as a function, but to the nature of the symbol x itself; that is to say, (ftx am-

—

—

biguously denotes

cjya,

biguously denotes

a, b, c, etc.

(j>b,

(f)C,

etc.,

only because

x am-

In short a propositional

function has ambiguous denotation,

if it

contains a term

having ambiguous denotation; whereas a propositional

unambiguous denotation, term having ambiguous denotation. function has

§

15.

if it

contains no

Hitherto, in illustrating Russell's account,

we

have taken the propositional function to be a function of a single variable, viz., of the symbol for the subject of the proposition, the predicate standing for a constant. It is obvious, however, that no proposition can be regarded as a function of a single variant unless the proposition is represented by a simple letter; and we will therefore take the specific propositional form 'x \s p' to illustrate a function of two variables. The variants of which this is a function would naturally be taken as the

CHAPfER

74

symbols

x and p

themselves

III

but, since Russell refuses

;

by

to allow a predicate or adjective to stand

takes as the two variables the subject term

with the symbolic variable 'x pression 'x is/'

may be

read

is

meant that instead of the

is

p,'

we suppose

leaving a blank.

if

we ought

subject-term,

we

in

together

symbolic ex-

';i:-blank is

/'; by which

full

propositional form 'x

x

is

omitted,

use a blank symbol for the

consistency to be allowed to

use a similar blank symbol for the predicate term.

would give the

same

nine combinations

rise to

propositional form: 'this

'this is/,' '^is hurt,' 'this

and

finally 'x is p.'

only 'this

is hurt,'

Of 'x

is

he

The

p.'

vs,

that the subject-term

But,

x

itself,

isjzJ*,'

all

This

of which are of

is hurt,'

'x

is

hurt,'

'^is/,' ^x is/,' 'x is/,'

these nine phrases, Russell uses

and 'x is hurt'; of which the two admittedly different

hurt'

the two latter illustrate meanings or applications of the general notion of the propositional function. Now, though

CHAPTER

82

some and denied by other

IV

philosophers,

the

together constitute an antilogism having the same

three illus-

trative value as our previous example.

Taking,

P

first,

and

Q

as asserted premisses

not-^ as conclusion, we obtain the

.*.

and

syllogistic inference

P.

All possible objects of thought have been sensationally impressed upon us;

Q.

Substance

not-i?.

is

a possible object of thought;

Substance has been sensationally impressed

upon

us.

With some explanations and

modifications this syllo-

gism represents roughly one aspect of the new

realistic

philosophy.

P

R

Taking, next, and as asserted premisses and not-^ as conclusion, we have P.

R.

All possible objects of thought have been sensationally impressed upon us;

Substance has not been sensationally impressed

upon .

•.

not-^.

us;

Substance

is

not a possible object of thought.

This syllogism represents very

fairly

the position of

Hume. Taking,

lastly,

R and Q as

not-/* as conclusion,

asserted premisses

and

we have

R. Substance has not been sensationally impressed upon us; Q. .

'.

Substance

is

a possible object of thought;

Not every possible object of thought has been sensationally impressed upon us.

not-/*.

This syllogism represents almost precisely the wellknown position of Kant.

THE CATEGORICAL SYLLOGISM As

83

our previous example these three syllogisms

in

are respectively in figures

i, 2,

and

3; and,

moreover,

Kant's argument in figure 3 has both a destructive function in upsetting Hume's position; and a constructive

function in suggesting

replacement of the

the

by a limited universal which would

particular conclusion

assign the further characteristic required for discrimi-

nating those objects of thought which have not been

obtained by experience from those which have been thus obtained. §

6.

Since the

dicta,

as formulated above, apply

only where two of the propositions are singular or instantial, they must be reformulated so as to apply also where all the propositions are general, i.e. universal or

particular.

Furthermore, they

determine directly figure.

As

all

will

be adapted so as to

the possible variations for each

follows:

Dictum for Fig. i if Every one of a

C

certain class possesses (or lacks) a certain property and Certain objects S are included in that class C, then These objects S must possess (or lack) that property P.

P

Dictum for Fig. 2 if Every one of a

certain class C possesses (or lacks) a certain property and Certain objects 6" lack (or possess) that property/*, then These objects 6" must be excluded from the

P

class C.

Dictum, for Fig. 3 if Certain objects perty

.S

possess (or lack) a certain pro-

P

6—2

CHAPTER

84

IV

and These objects ^ are included in a certain class C Not every one of the class C lacks (or possesses)

then

i.e.

that property P. Some of the class

C

possess (or lack) that pro-

perty P. In each of these dicta the word 'objects,' symbolised as S, represents the term that stands as subject in both its

occurrences; the word 'property' P, the term that

stands as predicate in both

word 'class' C, and again as

its

occurrences; and the

that term which occurs once as subject

Hence, using the symbols

predicate.

S, C, P, the first three figures are thus schematised I

Fig. 2

Fig. 3

C-P S-C S-P

C-P S-P S-C

S-P S-C C-P

Fig.

.-.

§ 7.

.-.

In order systematically to establish the

which are valid should be noted

S—P

.-.

is

in in

accordance with the above

moods dicta,

it

each figure (i) that the proposition

unrestricted

as

regards

both quality and

S—C

quantity; (2) that the proposition is independently fixed in quality, but determined in quantity by

the quantity of the unrestricted proposition the proposition

;

and

C — P\s, independently fixed in

(3) that

quantity,

but determined in quality by the quality of the unrestricted

proposition.

conclusion

is

Thus

unrestricted, the

in

Fig.

i,

minor premiss

while is

the

indepen-

dently fixed in quality but determined in quantity by the quantity of the conclusion; and the major premiss is

independently fixed

quality

in

quantity but determined in

by the quality of the conclusion.

while the minor premiss

is

In Fig.

2,

unrestricted, the conclusion

THE CATEGORICAL SYLLOGISM is

independently fixed

85

quality but determined in

in

quantity by the quantity of the minor premiss

;

and the

major premiss is independently fixed in quantity, but determined in quality by the quality of the minor preIn Fig.

miss.

3,

while the major premiss

the minor premiss

determined

is

is

unrestricted,

independently fixed in quality but

in quantity

by the quantity of the major

premiss, and the conclusion

is

independently fixed in

quantity but determined in quality by the quality of the

major premiss.

Having

in the

each case which

which or

is

/or

Fig.

2,

is

above dicta

is

phrase in

directly restrictive, the proposition

unrestricted,

O,

italicised the

may be

i.e.

of the form

seen to be: in Fig.

the minor premiss

or

B

the conclusion; in

1,

in Fig. 3, the

;

A

major premiss.

Hence each of these figures contains four fundamental moods derived respectively by giving to the unrestricted proposition the form A, E, I or O. Besides these four fundamental moods there are also supernumerary moods. These are obtained by substituting, in the conclusion, a particular for a universal;

or, in

a universal for a particular; universal for a particular.

or, in

the minor premiss, the major again, a

These supernumerary moods

be said respectively to contain a weakened conclusion, a strengthened minor, or a strengthened will

major; and, in the scheme given the propositions thus

the next section,

weakened or strengthened

be indicated by the raised

may

in

letters

w

or

.$•

will

as the case

be.

§ 8.

Adopting the method above explained, we may

now

formulate the special rules for determining the

valid

moods

in

each figure as follows

CHAPTER

86

Rules for Fig.

The quality

IV

i

conclusion being unrestricted in regard both to

and quantity,

The major

{a)

versal,

and

premiss must in quality agree

in quantity be uniwith the conclusion.

The minor premiss must be

{b)

tive,

and

in

in quality affirma-

quantity as wide as the conclusion.

Rules for Fig. 2. The minor premiss being unrestricted to quality (a)

The major versal,

[b)

The and

and

to quantity

premiss must be in quantity uniopposed to the minor.

conclusion must be in quality negative, narrow as the minor.

in quantity as

and

The and

[b)

in

regard both

quality,

conclusion must in quantity be particular, agree with the major,

in quality

The minor premiss must tive,

and

Italicising in

we may

regard both

in quality

Rules for Fig. 3. The major premiss being unrestricted

(a)

in

and quantity,

in

in quality be affirmaquantity overlap^ the major.

each case the unrestricted proposition,

moods

represent the valid

for the first three

figures in the following table:

Valid Moods for the

"

One-Class " Figures.

Fundamentals Fig.

AA^

Fig. 2

E^E

Fig. 3

AW

^

is

I

EA^

The minor and major

universal^ not otherwise.

AI/

will necessarily

overlap

if

one or the other

THE CATEGORICAL SYLLOGISM Having

§ 9.

d>7

moods of the first antilogism, we proceed to

established the valid

three figures from a single

construct those of the fourth figure also from a single

antilogism; thus:

Taking any three

classes,

it is

impossible that

The first should be wholly included in the second The second is wholly excluded from the third and The third is partly included in the first. The validity of this antilogism is most naturally

while

realised

by representing

a representation

is

classes as closed figures.

in fact valid,

Such

although the relation

of inclusion and exclusion of classes

with the logical relations expressed negative propositions respectively;

is

not identical

in affirmative for,

there

is

and

a true

analogy between the relations between classes and the

between closed

relations

between the

figures; in that the relations

relations of classes are identical with the

corresponding relations between the relations of closed

Thus adopting

figures.

as the

scheme of the fourth

figure

the above antilogism will be thus symbolised It is

impossible to conjoin the following three pro-

positions

:

P.

Every

C^

Q.

No

is

R.

Some

C2

C^

is C^,

C3, is C,.

This yields the three fundamental syllogisms (i)

If

/'and Q, then not-^?; i.e. if Every C^ is C^ and then

No No

C2

is C^,

C

is

C-

CHAPTER

88 If

(2)

Q

IV

and R, then not-P; if

No

C2

and Some C^

i.e.

C3

is

is C^,

then Not every C^ If 7?

(3)

and P, then not-^ if

Some

C^

Since the propositions

arranged

C

Some

Cj

C,

is is

of

C„.

i.e.

;

is

and Every C^ then

is

C3.

syllogisms

these

in canonical order, the valid

fourth figure can be at once written

down

moods

are

in the

ABE, B/0,

:

Moreover, since the conclusion of the first mood it may be weakened; since the minor of the second is particular, it may be strengthened; and since the major of the third is particular, it also may be

lAI. is

universal,

This yields:

strengthened.

Valid Moods of the Fourth Figure. Fundamentals

Supernumeraries \v

AEE

EIO

AEO

lAI

s

Here each supernumerary can only be one sense,

AAI

interpreted in

as containing respectively a

viz.,

s

EAO

weakened

conclusion, a strengthened minor, and a strengthened

major.

In contrast to

this,

the supernumeraries of the

first and second figures must be interpreted as containing either a weakened conclusion or a strengthened

and those of the third figure as containing either a strengthened major or a strengthened minor, minor;

§"10.

An

antiquated prejudice has long existed

against the inclusion of the fourth figure in logical doctrine,

and

in

support of this view the ground that

has been most frequently urged

is

as follows:

THE CATEGORICAL SYLLOGISM

Any argument worthy

89

of logical recognition must

be such as would occur in ordinary discourse. Now it will be found that no argument occurring in ordinary discourse is in the fourth figure. Hence, no argument in the fourth figure is worthy of logical recognition. This argument, being in the fourth figure, refutes itself; and therefore needs to be no further discussed. §

1

Having formulated

1.

certain intuitively evident

observance of which secures the validity of

dicta, the

the syllogisms established by their means,

we

will pro-

ceed to formulate equally intuitive rules the violation will render syllogisms invalid. These rules

of which will

be found to rest upon a single fundamental conour data or premisses refer to some no conclusion can be validly drawn to all members of that class. This is

sideration, viz.

only of a

which

if

class,

refers

technically expressed in the rule: (i)

'No term which

may be

undistributed in

is

its

premiss

distributed in the conclusion.'

This rule alone but from

validity,

is

not sufficient directly to secure

it

we can deduce

other directly

applicable rules which, taken in conjunction with the first, will

be sufficient to establish directly the invalidity

of any invalid form of syllogism.

we

deducinof these other rules

shall

In the course of

make

use of certain

from their emdeductive process, of which the follow-

logical intuitions that are obvious apart

ployment in this ing may be mentioned: {a) that if a term proposition,

proposition

it ;

will

distributed in any given

is

be undistributed

and conversely,

in a given proposition,

it

if

will

in

the contradictory

a term

is

undistributed

be distributed

in

the

CHAPTER

90

IV

That this

contradictory proposition.

is

so

is

directly seen

grounds that only when it has been accepted on universals distribute the subject term, and only negaproposition is tives the predicate term; and that an contradicted by an O, and an / proposition by an E. (3) That any syllogism can be expressed as an antilogism and conversely. This principle follows from the intuitive apprehension of the relation between imintuitive

A

and disjunction.

plication

That

{c)

tuition

is

formally possible for any three

is

it

terms to coincide

(This particular in-

in extension.

employed

the rejection of only one form of

in

syllogism.)

We

now

are

original principle,

{b\ and

{c),

a

in

position

from rule

i.e.

to

deduce from our

by means of {a)y application of which

(i),

other rules, the direct

exclude any invalid forms of syllogism.

will

(2)

'The middle term must be distributed

in

one or

other of the premisses.'

To

establish

which disjoins P,

this,

Q

to the syllogism 'If

the syllogism 'l[ first

of these,

if

P

us consider the antilogism

let

and

7?; this,

by

{b) is

equivalent

P and

Q, then not-7?' and also to and P, then not-^.' Taking the

a term

X

is

undistributed in the premiss

must be undistributed in the conclusion not-7?, must, by (a), be distributed in P. Applying this result to the second syllogism If P and P, then not-^,' we have shown that if the middle term is undistributed in the premiss P, it must be distributed in the premiss P. This then establishes rule (2). (3) 'If both premisses are negative, no conclusion

P,

it

i.e. it

'

X

can be syllogistically inferred.'

THE CATEGORICAL SYLLOGISM

91

For, taking any two universal negative premisses,

these can be converted

and

'

No 5

is

J/'

;

(if

necessary) into

*

No

/*

is

M'

which, by obversion, are respectively

equivalent to 'All

P

non-J/' and 'All

is

5

is

non-J/,'

which the new middle term non-J/ is undistributed But this breaks rule (2). What in both premisses. holds of two universals will hold a fortiori if one or other of the two negative premisses is particular. Thus in

rule (3)

is

established.

'A negative premiss requires a negative con-

(4)

clusion.'

For, taking again the antilogism which disjoins P, and R, this is equivalent both to the syllogism 'If/* and R, then not-^,' and to the syllogism '\{ P and Q, then not-/?.' Taking the first of these two syllogisms, by rule (3), if the premiss P is negative, the premiss R must be affirmative. Applying this result to the second

Q

syllogism,

we

have,

if

the premiss

P

conclusion not-/? must be negative.

is

negative, the

This establishes

rule (4). (5)

'A negative conclusion requires a negative

premiss.'

This

is

equivalent to the statement that two affirma-

tive premisses cannot yield a negative conclusion.

establish this rule,

we must

To

take the several different

figures of syllogism Fig.

Fig. 1

I

Fig. 3

Fig. 4

M-P S-M

P-M S-M

M-P M-S

P-M M-S

S-P

S-P

S-P

S-P

For the

first

or third figure, affirmative premisses

with negative conclusion would entail false distribution

CHAPTER

92

IV

which has been forbidden under our fundamental rule (i). Taking next the second figure, it would entail false distribution of the middle term, forbidden by rule (2), Finally taking the fourth figure,

of the major term

;

would either entail some false distribution forbidden by rules (i) and (2); or else yield the mood ^4^0 which would constitute a denial that three terms could coincide in extension, thus contravening (c). This establishes it

rule (5).

The five rules thus established may be resummed up into two rules of quality and

§ 12.

arranged and

two

rules of distribution, viz.

A. Rules of Quality. (^1)

(«o)

For an affirmative conclusion both premisses must be affirmative. For a negative conclusion the two premisses must be opposed in quality.

Rules of Distribution.

B.

{b^

The middle term must be least

(4)

distributed in at

one of the premisses.

No

term undistributed in its premiss distributed in the conclusion.

may be

These rules having been framed with the purpose of rejecting invalid syllogisms,

we may

first

point out that,

irrespective of validity, there are sixty-four abstractly

possible combinations of major, minor

The Rules

and conclusion.

of Quality enable us to reject en bloc

moods except those coming under the following heads, viz. those which contain (requiring

clusion

minor)

;

(ii)

affirmative

(i)

all

three

an affirmative con-

major and affirmative

a negative major (requiring affirmative

THE CATEGORICAL SYLLOGISM

93

minor and negative conclusion); (iii) a negative minor (requiring affirmative major and negative conclusion). This leads to the following table, which exhibits the 24 possibly valid moods unrejected by the Rules of Quality.

CHAPTER

94 /

Fig. clusion

Fig. ,

One

2.

must

premiss must be negative;

i.e.

con-

be negative.

One

3.

IV

or the other of the premisses

must be

universal.

2nd of the Major Term. Figs. I and 3. If the conclusion is negative, the major must be negative; i.e. (in either case) the minor mtist be affirmative.

Figs. 2 and 4. If the conclusion major must be universal.

is

negative, the

^rd of the Minor Term.

and 2. If the minor is particular, the conclusion must be particular. Figs. 3 and 4. If the minor is affirmative, the conclusion must be particular. Figs.

I

These rules have been grouped by reference to the term (middle, major or minor) which has to be correctly distributed. They will now be grouped by reference to the figure (ist, 2nd, 3rd or 4th) to which each applies. In this rearrangement we shall also simplify the formulations by replacing where possible a hypothetically formulated rule by one categorically formulated. As a basis of this reformulation

we

take the rules of quality

3, which have already been expressed categorically; viz. for Figs, i and 3: 'The minor premiss must be affirmative,' and for Fig. 2: 'The conclusion must be negative.' Conjoining the categorical

for Figs.

I,

2

and

rule (of quality) for Fig.

i

with

its

hypothetical rule,

minor is affirmative the major must be universal,' we deduce for this figure the categorical rule (of quantity), '

If the

'The major must be universal' Again, conjoining the

THE CATEGORICAL SYLLOGISM

•Lie (U

-^

1-

>-

«'5 ^ h

^

> 3

^

ei

.i^

S?-^-5=.°15§ (14

i.i°sli

^ o

c

l-cs

-s

rt

5

!£

.2

S~

rt

'35

ir

O c

Co

.28=2

< w

.H,

2

5 < w

^ •^

«o

w w

{A, B, C) for all values of A, B, C, where all the variables are variables

FUNCTIONAL DEDUCTION

127

and the equation therefore contains no such symbol as that can be exhibited as dependent upon the others. The distinction between these two typesof equation is familiarto mathematicians the former may be called a limiting, the latter a nonindependently variable,

P

The

limiting equation.

limiting equation

is

generally

used to determine one or other of the quantities P, A, B, or C, in terms of the remainder; so that here we associate the antithesis between dependent and independent with the antithesis between unknown and

known; whereas, in the non-limiting equation, no one of the variables can be regarded as unknown and as such expressible in terms of the others regarded as known. The distinctions that have been put forward between these two types of functional process are tanta-

mount

to defining the functional syllogism as that

which proves factual conclusions from factual premisses, and functional deduction as that which proves formal conclusions or formulae from formal premisses, i.e. from formulae previously established.

It will further be observed, from the simple illustrations which follow, that whereas the functional syllogism requires only the one

functional equation that serves as major premiss, the

process of functional deduction will necessarily involve

a conjunction of two or more functional equations, all of which are, as above explained, formal and not factual.

To

illustrate the

deduction,

/{a,

which

is

general formula used in functional

viz. b,

c,

...)

= (j){a,

b, c,

...)

understood to hold for every value of the

CHAPTER

128

A, B,

variables

C, ...,

VI

we may

instance the following

elementary examples: {a

and

+ d)x{a-d) = a'-d' axd = dxa,

both of which involve two variables; and again

=a + {d + c)

{a-{-d)-\-c

and

{a

+ d)xc

={axc)-\-(dxc),

The

both of which involve three variables. formulae are

known

last

three

respectively as the Commutative,

the Associative and the Distributive Law. § 4.

In the functional equations of mathematics

it

is

important to realise the range of universality covered by

any functional formula. This range depends upon the numberof independent variables involved in the formula, the range being wider or narrower according as the

num.ber of independent variables

For example, supposing 7, 5,

larger or smaller.

is

have respectively

that x, y, z

10 possible values; then the numberof applications

x

of the formula involving

involving

involving

number

x and y alone x and y and 2

alone

is 7,

that of a formula

and that of a formula

is

35,

is

350.

And

in general, the

of applications of a formula

is

equal to the

numbers of possible values for the variables involved. Now the number of possible values of any variable occurring in logical or mathe-

arithmetical product of the

matical formulae spectively of

I,

is 2,

infinite;

3...

hence, for the cases re-

variables, the

corresponding

00 \.., constiranges of application would be 00, 00 tuting a series of continually higher orders of infinity "^j

or rather, in accordance with Cantor's arithmetic, each of the ranges of application for

i,

2,

3

...

variables

is

a

FUNCTIONAL DEDUCTION proper part of that for cardinal

129

successor, although their

its

numbers are the same.

Now it will be found that,

in inferences of the

of functional deduction, the derived formula a range of application to or

Thus

— not narrower

the

answer

word deduction

may have

than but

even wider than that from which

it

nature

is

— equal

derived.

as here applied does not

to the usual definition of deduction (illustrated

especially in the syllogism) as inference from the generic to the specific;

although the only fundamental principle

employed in the process is the Applicative, according which we replace either a variable symbol by one of its determinates or one determinate variant by another. But here a distinction must be made according as the substituted symbol is simple or compound. If we merely replace any one of the simple symbols a, b, c by some other simple symbol we shall not obtain a really new to

formula, since the formula

is

for all substitutable values,

indifference whether

the symbols

a, b,

to be interpreted as holding and hence it is a matter of

we express

the formula in terms of

(say) or oi p, q,r.

c,

In order to deduce

new formulae, it is necessary to replace two or more simple symbols by connected compounds.

For those unfamiliar with mathematical methods, it when any compound symbol is substituted for a simple, the compound must be enclosed in a bracket or be shown by some device to

should be pointed out that,

constitute a single symbolic unit.

always replace

in

Though we may

a general formula a simple by a com-

pound symbol, the reverse does not by any means hold without exception. tion

is

The

cases in which such substitu-

permissible have been partially explained in the

J. L. II

9

CHAPTER

130

VI

chapter on Symbolism and Functions.

shown

that,

if

formula

a

involves

There

was

it

such compound

symbols or sub-constructs as f{a, b\ f{c, d) etc., and only such, where none of the simple symbols used in the one bracketed sub-construct occur in any of the others, then these bracketed functions are called dis-

connected.

It is in

the case of disconnected functions

that free substitutions of simple symbols for the

pound are

The

permissible.

reason for this

is

com-

that, for

the notion of a function of any given variants,

it

is

essential that these shall be variable independently of

one another.

Now, when

the different sub-constructs

or bracketed functions are connected with one another

through identity of some simple symbol, say clear that

these

we cannot contemplate

compounds without

its

a,

it

is

a variation of one of

involving a variation of the

other connected compounds.

Hence we should be

vio-

lating the fundamental principle of independent variability

of the variants,

if

we

freely substituted for such

connected compounds simple symbols which would have to

be understood as capable of independent variation.

Hence,

it is

only

when the various compounds involved

in a function are

unconnected, that for each of such

compounds a simple symbol may be § 5.

substituted.

Returning to the problem under immediate con-

sideration, a simple illustration from algebra will

show

how, by making appropriate substitutions in a given functional formula, we may demonstrate a new formula. Thus, having established the formula that for all values of X and

y (i)

we may substitute

{x+y)x{x-y)=x'-f for xa.ndy, respectively, the connected

FUNCTIONAL DEDUCTION compounds

a-\-b

and a

— b\ and

so deduce (by means of

the distributive law for multiplication

values of a and

131

etc.) that for all

b^

(ii)

\ab^{a-^by-(a-b)\

This is a new formula, different from the previous one, because the relation between a and b predicated in (ii) is different from the relation between x and y predicated in (i). Moreover the range of application for (ii) is no narrower than that for (i); for (i) applies for every diad or couple 'x tojK,' and (ii) for every diad or couple 'a to

handle this volume with care. The

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BOOK 160.J639 V JOHNSON # LOGIC

3

2

c.

1

T153 OOOOMTDS

fi

LOGIC PART

II

CAMBRIDGE UNIVERSITY PRESS CLAY, Manager

C. F.

LONDON

:

FETTER LANE,

E.C. 4

NEW YORK THE MACMILLAN :

CO.

BOMBAY CALCUTTA I MACMILLAN AND CO., Ltd. MADRAS ] TORONTO THE MACMILLAN CO. OF \

:

CANADA,

Ltd.

TOKYO MARUZEN-KABUSHIKI-KAISHA :

ALL RIGHTS RESERVED

Be

LOGIC PART

II

DEMONSTRATIVE INFERENCE DEDUCTIVE AND INDUCTIVE

BY

W.

E.

JOHNSON, M.A.

FELLOVl^ OF king's COLLEGE, CAMBRIDGE, SIDGWICK LECTURER IN MORAL SCIENCE IN THE

UNIVERSITY OF CAMBRIDGE

CAMBRIDGE AT THE UNIVERSITY PRESS 1922

'^\

.0-

CONTENTS INTRODUCTION PAGE §

I.

Application of the term

'

substantive

§

2.

Application of the term

'

adjective

§ 3.

Terms '

'

and

'

adjective

Epistemic character of assertive

§ 5.

The given presented under The paradox of implication '

*

.

'

.

.

.

.

.

.

'........... ...... .... ........ ......

' substantive universal

§ 4.

§ 6.

xi

'

'

contrasted with

'

particular

'

and

tie

.

certain determinables

§ 7. Defence of Mill's analysis of the syllogism

CHAPTER

xii

xiii

xiv xiv

xv xvii

I

INFERENCE IN GENERAL §

I.

...... .......

Implication defined as potential inference

% 2. Inferences involved in the processes of perception

and epistemic conditions for valid of the 'paradox of inference'

§ 3. Constitutive § 4.

The

and association inference. Examination .

Applicative and Implicative principles of inference

§ 5. Joint

employment of these

principles in the syllogism

§ 6.

Distinction between applicational and implicational universals. structural proposition redundant as minor premiss

§ 7.

Definition of a logical category in terms of adjectival determinables

§ 8. Analysis of the syllogism in terms of assigned determinables. illustrations of applicational universals . .

§ 9. § 10.

i

2

How

identity

The

may be

said to

be involved

in

.

.

every proposition

The

Further .

.

.17

.

20

formal principle of inference to be considered redundant as major premiss. Illustrations from syllogism, induction, and mathematical equality

............ ............

20

§11. Criticism of the alleged subordination of induction under the syllogistic principle

24

CONTENTS

vi

CHAPTER

II

THE RELATIONS OF SUB-ORDINATION AND CO-ORDINATION AMONGST PROPOSITIONS OF DIFFERENT TYPES §

I.

The

Counter-applicative and Counter-implicative principles required axioms of Logic and Mathematics . .

.... ....

27

in the philosophy of thought

31

for the establishment of the

§

z.

Explanation of the Counter-applicative principle

§3. Explanation of the Counter-implicative principle § 4.

§

5.

Significance of the

two inverse principles

........... .......

of super-ordination, sub-ordination and co-ordination amongst propositions

Scheme

scheme

§ 6. Further elucidation of the

CHAPTER

28

29

32

38

III

SYMBOLISM AND FUNCTIONS §1.

The

§ 2.

The

value of symbolism. Illustrative and shorthand symbols. Classification of formal constants. Their distinction from material constants .

system § 3.

§ 4.

....

41

nature of the intelligence required in the construction of a symbolic

44

The range

of variation of illustrative symbols restricted within some logical category. Combinations of such symbols further to be interpreted as belonging to an understood logical category. Illustrations of intelligence required in working a symbolic system

Explanation of the term

'

function,'

and of the

'

....

46

for a function

48

variants

'

§ 5. Distinction between fvinctions for which all the material constituents are variable, and those for which only some are variable. Illustrations

from logic and arithmetic § 6.

§

7.

The

......... .... ...... .....

various kinds of elements ofform in a construct

Conjunctional and predicational functions

§ 8.

Connected and unconnected sub-constructs

§ 9.

The

use of apparent variables in symbolism for the representation of the distributives every and some. Distinction between apparent variables and class-names

..........

50 53 55 57

58

§ 10. Discussion of compound symbols which do and which do not represent genuine constructs . . . .

§ It. Illustrations of

§12. Criticism of functions

genuine and

Mr

.

.

.

fictitious constructs

Russell's view of the relation

and the functions of mathematics

......61 ..... .... .

.

64

between propositional

§13. Explanation of the notion of a descriptive function § 14. Further criticism of Mr Russell's account of propositional functions §15. Functions of two or more variants

66

69

.

71

73

CONTENTS

CHAPTER

vii

IV

THE CATEGORICAL SYLLOGISM

.......-77 .......

PAGE

§

r.

Technical terminology of syllogism

§

2.

Dubious propositions to

76

illustrate syllogism

§3. Relation of syllogism to antilogism

.

.

.

.

78

.....

§ 4.

Dicta for the first three figures derived from a single antilogistic dictum, showing the normal functioning of each figure

§ 5.

Illustration of philosophical

§ 6.

arguments expressed in

form

§ 7.

The

§ 8.

Special rules and valid

all

the propositions

propositions of restricted and unrestricted form in each figure

§ 9. Special rules

and

valid

moods moods

for the fourth figure

§11. Proof of the rules necessary for rejecting invalid syllogisms.

.

of quality

84

... ....

for the first three figures

.

Summary

83

.

§ lo. Justification for the inclusion of the fourth figure in logical doctrine

§ 12.

79 81

.

...........

Re-formulation of the dicta for syllogisms in which are general

syllogistic

.

............ .... .......... .... ........... .........

of above rules; and table of

moods unrejected by

85 87

88 89

the rules

92

§13. Rules and tables of unrejected moods for each figure § 1 4. Combination of the direct and indirect methods of establishing the valid moods of syllogism

93

96

§15. Diagram representing the valid moods of syllogism § 16.

The

§ 17. Reduction of irregularly formulated arguments to syllogistic form § 18.

97

Sorites

97 98

.

Enthymemes

§19. Importance of syllogism

roo 102

CHAPTER V FUNCTIONAL EXTENSION OF THE SYLLOGISM §

I.

§ 2.

Deduction goes beyond mere subsumptive inference, when the major . . 103 premiss assumes the form of a functional equation. Examples functional equation is a universal proposition of the second order, the . . .105 functional formula constituting a Law of Co- variation.

A

§ 3.

The solutions of mathematical equations which yield single-valued func. . tions correspond to the reversibility of cause and effect

§ 4.

Significance of the

§

5.

§ 6.

.106

number of variables entering body falling in vacuo

into a functional formula

Example of a The logical characteristics of connectional equations illustrated by thermal .

.

.

.

.

.

.

108 1

10

. .111 and economic equilibria The method of Residues is based on reversibility and is purely deductive 1 16 . 119 §8. Reasons why the above method has been falsely termed inductive .

§

.

.

.

.

.

.

7.

§ 9.

Separation of the subsumptive from the functional elements in these . . . extensions of syllogism .

.

.

.

.

.120

vm

CONTENTS

CHAPTER

VI

FUNCTIONAL DEDUCTION §1. In the deduction of mathematical and logical formulae, new theorems are established for the different species of a genus, which do not hold for the genus . . .123

....... .........

.

.

§2. Explanation of the Aristotelean

.

.

.

.

.

.

tdiov

125

§3- In functional deduction, the equational formulae are non-limiting.

Elementary examples §4-

126

The range

of universality of a functional formula varies with the number of independent variables involved. Employment of brackets. Importance of distinguishing between connected and disconnected compounds

128

The

functional nature of the formulae of algebra accounts for the possibility of deducing new and even wider formulae from previously established and narrower formulae, the Applicative Principle alone being

employed

.

.

.

.

§6. Mathematical Induction

§7.

The

logic of

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

mathematics and the mathematics of logic

§8. Distinction between premathematical and mathematical logic

-130 -133 -135 .138

.

§9- Formal operators and formal relations represented by shorthand and not variable symbols. Classification of the main formal relations according to theis properties . . . .141 .

.

.

The material variables

§ Il-

.

.

...... ...... .....

of mathematical and logical symbolisation receive specific values only in concrete science

144

Discussion of the Principle of Abstraction

145

The

magnitude are not determinates of the single determinable Magnitude, but are incomparable ls-

specific kinds of

150

The

logical symbolic calculus establishes y^rwMto of implication which are to be contrasted with the principles of inference employed in the

procedure of building up the calculus

.

.

.

.

.

-151

.

CHAPTER Vn THE DIFFERENT KINDS OF MAGNITUDE §

I.

§ 2.

The terms

'greater' and 'less' predicated of magnitude, 'larger' 'smaller' of that which has magnitude

Integral

number

and

as predicable of classes or enumerations

§ 3. Psychological exposition of counting

.

§ 4. Logical principles underlying counting § 5. One-one correlations for finite integers

153

154 155 158

160

§ 6.

Definition of extensive magnitude

161

§

Adjectival stretches compared with substantival

163

7.

.... .......

§ 10.

Comparison between extensive and extensional wholes Discussion of distensive magnitudes Intensive magnitude

172

§ II.

Fundamental

173

§ 8. § 9.

distinction

between distensive and intensive magnitudes

166 168

CONTENTS

ix

PAGE §12. The problem of equality of extensive wholes

174

§ 13. Conterminus spatial and temporal wholes to be considered equal, quali tative stretches only comparable by causes or effects

175

.

....

Complex magnitudes derived by combination of simplex §15. The theory of algebraical dimensions § 16. The special case in which dividend and divisor are quantities same kind § 14.

.

.........

§

1

7.

Summary

of the above treatment of magnitude

CHAPTER

180 185 of the

186 187

.

VIII

INTUITIVE INDUCTION The general antithesis between induction and deduction The problem of abstraction §3. The principle of abstractive or intuitive induction

§

t.

§ 2.

.

.

.

.

.

.

.

.

.

.189 .

.

.

§4. Experiential and formal types of intuitive induction §5. Intuitive induction involved in introspective and ethical judgments § 6. Intuitive inductions upon sense-data and elementary algebraical and .

logical relations

.

.

.

.

.

§7. Educational importance of intuitive induction

CHAPTER

.

.

.

.

.

.

.

.

1

90

.191

.... .

192

193

'194 .196

IX

SUMMARY INCLUDING GEOMETRICAL INDUCTION Summary Summary

induction reduced to

§ 2.

§ 3.

Summary

induction involved in geometrical proofs

§ 4.

Explanation of the above process

§ 5.

Function of the figure

§.6.

Abuse of

§

I

first

figure syllogism

197

.

..... ...... .... ..... .....

induction as establishing the premiss for induction proper. Criticism of Mill's and Whewell's views

1

98

200 201

in geometrical proofs

203

the figure in geometrical proofs

205

208

§7. Criticism of Mill's 'parity of reasoning'

CHAPTER X DEMONSTRATIVE INDUCTION §

I.

Demonstrative induction uses a composite along with an instantial premiss . . .210 .

.

.

.

.

.

.

.

arguments leading up

.

§ 2.

Illustrations of demonstrative

§ 3.

Conclusions reached by the conjunction of an alternative with a junctive premiss . . . . .

induction

.

.

.

.

.

.

.

.

.

.

to demonstrative .

.

.

.

.210 dis-

.214 as

CONTENTS

X

PAGE §4.

The formula

of direct univcrsalisation

§5. Scientific illustration of the above

....... .

.

.

.

.

.215

§

7.

§8.

217

of others

csiS

The

.

.

.

.

.

.

.

Figure of Agreement

.

.

.

.

.

.......... .......... ......... ......... .....

four figures of demonstrative induction

§ 9. Figure of Difference § 10.

216

methods of induction The major premiss for demonstrative induction as an expression of the dependence in the variations of one phenomenal character upon those

§ 6. Proposed modification of Mill's exposition of the

.

.

.

.

.221 222

223

§11. Figure of Composition

224

§12. Figure of Resolution

226

.

......

§13. The Antilogism of Demonstrative Induction §14. Illustration of the Figure of Difference §15. Illustration of the Figure of Agreement § 16.

.

.

.

.

.

.

.

.

§ 17. Modification of symbolic notation in the figures where different cause. factors represent determinates under the same determinable .

§ 18. § 19.

228

•'^31

Principle for dealing with cases in which a number both of cause-factors effect-factors are considered, with a symbolic example

and

226

232

234

between the two last and the two first figures Explanation of the distinction between composition and combination

235

of cause-factors

235

The

striking distinction

.

.

..........

§20. Illustrations of the figures of Composition and Resolution

CHAPTER

.

.

.

237

XI

THE FUNCTIONAL EXTENSION OF DEMONSTRATIVE INDUCTION

....... '............ ..........

The major

premiss for Demonstrative Induction must have been estabby Problematic Induction 240 .241 §2. Contrast between my exposition and Mill's .242 § 3. The different uses of the term hypothesis in logic §4. Jevons's confusion between the notions 'problematic' and 'hypothetical 244 §

I.

lished

.

'

§ 5.

The

'

.

.

.

.

.

.

establishment of a functional formula for the figures of Difference

and of Composition § 6.

The

formula §

7.

A

............ ............

criteria of simplicity

comparison of

these

and analogy

criteria

with similar criteria proposed

formula

INDEX

methods

for

249

by

Whewell and Mill

§ 8. Technical mathematical

246

for selection of the functional

251

determining the most probable 252

254

INTRODUCTION TO PART §

in

Before introducing the

I.

Part II,

I

topics to be

II

examined

propose to recapitulate the substance of

Part I, and in so doing to bring into connection with one another certain problems which were there treated I hope thus to lay different emsome of the theories that have been mainand to remove any possible misunderstandings

in different chapters.

phasis upon tained,

where the treatment was unavoidably condensed. In my analysis of the proposition I have distinguished the natures of substantive and adjective in a form intended to accord in essentials with the doctrine of the large majority of logicians, is

new its

and as

far as

my terminology

novelty consists in giving wider scope to each

of these two fundamental terms. Prima facie it might be supposed that the connection of substantive with adjective in the construction of a proposition

mount

is

tanta-

to the metaphysical notions of substance

inherence.

But

my

notion of substantive

and

intended

is

to include, besides the metaphysical notion of substance

— so

far as this

can be philosophically justified

tion of occurrences or events to

—the no-

which some philosophers

of the present day wish to restrict the realm of reality.

Thus by

a substantive /r^/^r

the category of the existent

I

is

mean an

and divided into the two existent;

subcategories: what continues to exist, or the continuant;

and what ceases

to exist, or the occurrent,

rent being referrible to a continuant.

To

every occurexist

is

to be

INTRODUCTION

xii

in

temporal or spatio-temporal relations to other exis-

and these relations between existents are the

tents;

A

fundamentally external relations. cannot characterise, but

is

substantive proper

necessarily characterised

;

on

other hand, entities belonging to any category whatever (substantive proper, adjective, proposition,

the

etc.)

may be

characterised by adjectives or relations

belonging to a special adjectival sub-category corresponding, in each case, to the category of the object

which

it

characterises.

Entities, other than substantives

proper, of which appropriate adjectives can be predicated, function as quasi-substantives.

The term

§ 2.

a wider range than usual, for that

it

my

adjective, in it is

application, covers

essential to

my system

There are two

should include relations.

distinct

points of view from which the treatment of a relation as of the

same

defended.

logical nature as an adjective

In the

first

a relational proposition

may be

place the complete predicate in is,

in

my

view, relatively to the

subject of such proposition, equivalent to an adjective in the '

He

is

ordinary sense.

For example,

in

afraid of ghosts,' the relational

pressed by the phrase 'afraid

of

;

the proposition,

component

is

ex-

but the complete

predicate 'afraid of ghosts' (which includes this relation)

has

all

the logical properties of an ordinary adjective,

so that for logical purposes there tinction

between such a

tional predicate.

component it

in

is

no fundamental

relational predicate

In the second place,

such a proposition

is

if

and an

disirra-

the relational

separated,

I

hold that

can be treated as an adjective predicated of the sub-

stantive-couple 'he' and 'ghosts'. In other words, a relation cannot be identified with a class of couples,

i.e.

be

INTRODUCTION conceived extensionally

;

xiU

but must be understood to

be conceived intensionally. It no controvertible problem thus to include relations under the wide genus adjectives. It is compatible, for example, with almost the whole of Mr characterise couples,

seems

to

me

i.e.

to raise

Russell's treatment of the proposition in his Principles of

Mathematics-, and, without necessarily entering into the

emerge in such philosophical discussions, I hold that some preliminary account of relations is required even in elementary logic. My distinction between substantive and adjec§ 3. tive is roughly equivalent to the more popular philosophical antithesis between particular and universal; the Thus I notions, however, do not exactly coincide. controvertible issues that

understand the philosophical term particular not to apply to quasi-substantives, but to be restricted to substantives

even more narrowly to occurrents. On the other hand, I find a fairly unanimous opinion in favour of calling an adjective predicated of proper,

existents, or

i.e.

a particular subject, a particular

—the

name

universal

being confined to the abstract conception of the adjective. Thus red or redness, abstracted from any specific

judgment,

is

manifested

in

held to be universal;

a particular object of perception, to be

Furthermore, qua particular, the ad-

itself particular.

jective

is

but the redness,

said to be an existent, apparently in the

sense as the object presented to perception tent.

To me

it is

difficult to

a factor

I

regard

in the real

jectively real

is

it ;

an

same exis-

argue this matter because,

while acknowledging that an adjective universal,

is

may be

called a

not as a mere abstraction, but as

and hence,

in

holding that the ob-

properly construed into an adjective

INTRODUCTION

xiv

characterising a substantive, the antithesis between the

and the universal (i.e. in my terminology between the substantive and the adjective) does not

particular

involve separation within the

for thought,

in the

real,

but solely a separation

sense that the conception of the

substantive apart from the adjective, as well as the

conception of the adjective apart from the substantive, equally entail abstraction. § 4.

Again, taking the whole proposition constituted

by the connecting of substantive with maintained that tion

is

to

adjective,

have

I

in a virtually similar

sense the proposi-

be conceived as abstract.

But, whereas the

characterising

may be

tie

called constitutive in

its

func-

tion of connecting substantive with adjective to construct the proposition, tie

I

have spoken of the assertive

as epistemic, in the sense that

it

connects the thinker

with the proposition in constituting the unity which

may

be called an act of judgment or of assertion. When, however, this act of assertion becomes in its turn an object of thought,

the existent

for

;

it is

conceived under the category of

such an act has temporal relations to

other existents, and

is

necessarily referrible to a thinker

Though, relatively to the primary proposition, the assertive tie must be conceived conceived as a continuant. as epistemic

;

yet, relatively to the

secondary proposition

which predicates of the primary that

by A, the

it

has been asserted

assertive tie functions constitutively.

In view of a certain logical condition presup§ 5. posed throughout this Part of my work, I wish to re-

mind the reader of

that aspect of

proposition, according to which

that which

is

I

my

analysis of the

regard the subject as

given to be determinately characterised

INTRODUCTION

Now

by thought.

characterised by

I

some

xv

hold that for a subject to be

it must have been presented as characterised by the corresponding adjectival determinable. The fact that what is given is characterised by an adjectival determinable

adjectival determinate,

first

is

constitutive

characterised

;

but the fact that

is

it is presented as thus Thus, for a surface to be

epistemic.

characterised as red or as square,

been constructed

it

must

first

have

thought as being the kind of thing that has colour or shape for an experience to be in

;

characterised as pleasant or unpleasant,

have been constructed that has hedonic tone.

in

it

must

first

thought as the kind of thing

Actually what

is given, is to be determined with respect to a conjunction of several specific aspects or determinates and these determine the category to which the given belongs. For example, ;

'

'

on the dualistic view of reality, the physical has to be determined under spatio-temporal determinables, and the psychical under the determinable consciousness or

same being can be characterised as two-legged and as rational, he must be put into the experience.

If the

category of the physico-psychical.

The passage from

§ 6.

those in Part

II, is

tion to inference.

Part

I,

as

was

it

tion.

topics treated in Part

I

to

equivalent to the step from implica-

The term

inference, as introduced in

did not require technical definition or analysis,

It

sufficiently well

understood without explana-

was, however, necessary in Chapter III to in-

dicate in outline one technical difficulty connected with

the paradox of implication and there I what will be comprehensively discussed ;

chapter of this Part, that implication

is

first

in

hinted,

the

first

best conceived

INTRODUCTION

xvi

While

as potential inference.

implication and inference

for

elementary purposes

may be regarded as

practically

was pointed out in Chapter III that there is nevertheless one type of limiting condition upon which depends the possibility of using the relation of implica-

equivalent,

it

tion for the purposes of inference.

Thus

reference to

the specific problem of the paradox of implication

was

unavoidable

in Part I, inasmuch as a comprehensive account of symbolic and mechanical processes necessarily

included reference to

all

possible limiting cases; but,

apart from such a purely abstract treatment, no special logical

importance was attached to the paradox.

The

was that of the permissible employment of the compound proposition 'If/> then ^,'in the limiting case referred to

unusual circumstance where knowledge of the truth or the falsity oi p or of ^ was already present

when

the com-

pound proposition was asserted. This limiting case will not recur in the more important developments of inferwill be treated in the present part of my logic. might have conduced to greater clearness if, in Chapters III and IV, I had distinguished when using the phrase implicative proposition between the primary and secondary interpretations of this form of proposition. Thus, when the compound proposition Tf/ then q' is rendered, as Mr Russell proposes, in the form 'Either not-/ or q^ the compound is being treated as a primary proposition of the same type as its components / and q. When on the other hand we substitute for Tf / then q' the phrase 'p implies q^ or preferably 'p would imply q^ the proposition is no longer primary, inasmuch

ence that It

—

as

it

—

predicates about the proposition q the adjective

'implied

by/' which renders

the

compound

a secondary

INTRODUCTION

xvu

proposition, in the sense explained in Chapter

V\ Now

I

whichever of these two interpretations is adopted, the is legitimate under certain limiting conditions is the same. Thus given the compound Either inference which

'

not-/ or q' conjoined with the assertion of infer

'

q

we

'/,'

could

just as given 'p implies q' conjoined with the

\

assertion of

'/,'

we

infer ^q!

reason that

It is for this

become merged into one the ordinary symbolic treatment of compound pro-

the two interpretations have in

and

positions;

normal cases no distinction

in

is

made

regard to the possibility of using the primary or secondary interpretation for purposes of inference. The in

normal

case,

however, presupposes that

entertained hypothetically;

when

this

the danger of petitio principii enters.

Part

it

was only a very

I

which

this fallacy

will

special

p

does not obtain,

The problem

and technical case

has to be guarded against

be dealt with

in its

and q are

;

in

more concrete and

Part

in

in II,

philoso-

phically important applications. § 7.

The mention

of this fallacy immediately sug-

gests Mill's treatment of the functions and value of the

syllogism; but, before discussing his views, to consider

what

charge of petitio

I

propose

main purpose was in tackling the principii that had been brought against his

the whole of formal argument, including in particular the syllogism.

In the

first

section of his chapter, Mill

—

two opposed

classes of philosophers the one regarded syllogism as the universal type of all logical reasoning, the other of whom regarded syllogism refers to

of

whom ^

The

secondary

interpretation of the impHcative form '/ implies q' as is

developed in Chapter

III, § 9,

where the modal adjectives

necessary, possible, impossible, are introduced.

INTRODUCTION

xviii

as useless on the

ground that

involve petitio principii.

all

He

such forms of inference

then proceeds:

believe

'I

both these opinions to be fundamentally erroneous,' and this would seem to imply that he proposed to relieve the syllogism from the charge.

I

believe, however, that

—

all logicians who have referred to Mill's theory group which includes almost everyone who has written on the subject since his time have assumed that the purport of the chapter was to maintain the charge of petitio principii, an interpretation which his opening reference to previous logicians would certainly not seem to bear. His subsequent discussion of the subject is, verbally at least, undoubtedly confusing, if not self-contradictory; but my personal attitude is that, whatever may have been Mill's general purpose, it is from his own

—

exposition that

I,

in

common

with almost

his con-

all

temporaries, have been led to discover the principle

according to which the syllogism can be relieved from the incubus to which In

of Aristotle.

my

it

had been subject since the time

view, therefore, Mill's account of

the philosophical character of the syllogism trovertible

;

I

would only ask readers

is

incon-

to disregard

from

the outset any passage in his chapter in which he

appears to be contending for the annihilation of the syllogism as expressive of any actual Briefly his position

may be

mode

of inference.

thus epitomised.

Taking

a typical syllogism with the familiar major 'All

men

are mortal,' he substituted for 'Socrates' or 'Plato' the

minor term 'the Duke of Wellington' who was then living. He then maintained that, going behind the syllogism, certain instantial evidence

tablishing the major;

is

required for es-

and furthermore that the

validity

INTRODUCTION of the conclusion that the

Duke

of

xix

WelHngton would

die depends ultimately on this instantial evidence. interpolation of the universal major

'

All

men

The

will die

has undoubted value, to which Mill on the whole did justice; but he pointed out that the formulation of this

universal adds nothing to the positive or factual data

upon which the conclusion depends. It follows from his exposition that a syllogism whose major is admittedly established by induction from instances can be relieved from the reproach of begging the question or circularity if, and only if, the minor term is not included in the

The Duke of Wellington being have formed part of the evidence upon which the universal major depended. It was thereultimate evidential data. still

living could not

fore part of Mill's logical standpoint to maintain that

there were principles of induction by which, from a limited

number

of instances, a universal going

these could be logically justified.

beyond

This contention may

be said to confer constitutive validity upon the inductive process.

It is directly

associated with the further con-

sideration that an instance, not previously examined,

may

be adduced to serve as minor premiss for a syllogism,

and

that such an instance will always preclude circularity

in the formal process.

Now the

charge of circularity or

is epistemic; and the whole of Mill's argument may therefore be summed up in the statement that the epistemic validity of syllogism and the constitutive validity of induction, both of which had been disputed by earlier logicians, stand or fall together.

petitio principii

In order to prevent misapprehension in regard to Mill's

view of the syllogism,

it

must be pointed out that

he virtually limited the topic of his chapter to cases

in

INTRODUCTION

XX

which the major premiss would be admitted by all logicians to have been established by means of induction in the ordinary sense, i.e. by the simple enumeration of instances; although many of them would have contended that such instantial evidence was not by itself sufficient. Thus all those cases in which the major was otherwise established, such as those based on authority, intuition or demonstration, do not

Unfortunately

solution.

have confused

his

fall

all

within the scope of Mill's the commentators of Mill

view that universals cannot be

in-

tuitively but only empirically established, with his specific is

contention in Chapter IV.

I

admit that he himself

largely responsible for this confusion,

and

therefore,

while supporting his view on the functions of the syllogism,

I

must deliberately express

my

opposition to

his doctrine that universals can only ultimately

be estab-

and limit my defence to his analysis of those syllogisms in which it is acknowledged that the major is thus established. Even here his doctrine that all inference is from particulars to particulars is open to lished empirically,

fundamental criticism

;

my

and, in

treatment of the

principles of inductive inference which will be developed in Part III,

shall substitute

I

an analysis which

will

take account of such objections as have been rightly

urged against

Mill's exposition.

[Note. There are two cases

employed

in Part II differs

in

from that

which the technical terminology in Part I.

Part

Part

11, logically as

equivalent to axiom.

Part

I,

I,

is

applies to the form of a

a principle of inference.]

(i)

The

phrase /nW-

to be understood psychologically; in

tive proposition, in

compound

(2)

Counter-impiicative, in

proposition; in Part II, to

CHAPTER

I

INFERENCE IN GENERAL Inference

§ I.

is

a mental process which, as such,

has to be contrasted with impHcation.

The

connection

between the mental act of inference and the relation is analogous to that between assertion and

of implication

the proposition. Just as a proposition tially assertible,

two propositions bility

is

what

is

poten-

so the relation of implication between is

an essential condition for the possi-

of inferring one from the other; and, as

it

is

impossible to define a proposition ultimately except in

terms of the notion of asserting, so the relation of implication can only be defined

in

terms of inference.

This consideration explains the importance which

I

attach to the recognition of the mental attitude involved in inference

and assertion afterwhich the ;

strictly logical

question as to the distinction between valid and invalid inference can be discussed.

To distinguish

the formula

of implication from that of inference, the former

may

be symbolised *If/ then q^ and the latter 'p therefore q,' where the symbol q stands for the conclusion and^ for the

premiss or conjunction of premisses.

The ference

proposition or propositions from which an inis

made being

position inferred being

commonly supposed

called premisses,

called

the

and the pro-

conclusion,

it

first presented in thought, and that the transifrom these to the thought of the conclusion is the

positions tion J.

is

that the premisses are the pro-

L. II

I

CHAPTER

2

step in the process.

last

usually the case

;

that

is

But

I

fact the reverse

in

to say,

we

first

is

entertain in

thought the proposition that is technically called the conclusion, and then proceed to seek for other propositions which would justify us in asserting

conclusion may, on the one hand,

first

it.

present

The

itself to

us as potentially assertible, in which case the mental

process of inference consists in transforming what was potentially assertible into a proposition actually asserted.

On

we may have already

the other hand,

satisfied

ourselves that the conclusion can be validly asserted apart from the particular inferential process, in which

case

we may

yet seek for other propositions which,

functioning as premisses, would give an independent or additional justification for our original assertion.

In

every case, the process of inference involves three distinct assertions

tion q.'

oV ql and It

:

first

the assertion of

*/,'

next the asser-

would imply would imply q^ which is

thirdly the assertion that ^p

must be noted that

'/

the proper equivalent of 'if/ then

^,' is

the

more

correct

expression for the relation of implication, and not 'p

—

which rather expresses the completed inThis shows that inference cannot be defined in terms of implication, but that implication must be defined in terms of inference, namely as equivalent to potential inference. Thus, in inferring, we are not

implies q' ference.

merely passing from the assertion of the premiss to the assertion of the conclusion, but

we

are also implicitly

asserting that the assertion of the premiss

is

used to

justify the assertion of the conclusion. § 2.

Some

importance

in

difficult

problems, which are of special

psychology, arise

in

determining quite

INFERENCE IN GENERAL

3

precisely the range of those mental processes which

may be

called inference: in particular,

tion or inference

is

involved

in

how

far asser-

the processes of asso-

and of perception. These difficulties have been aggravated rather than removed by the quite false antithesis which some logicians have drawn between logical and psychological inference. Every inference is a mental process, and therefore a proper topic for psychological analysis on the other hand, to infer is to think, and to think is virtually to adopt a logical attitude; for everyone who infers, who asserts, who thinks, intends to assert truly and to infer validly, and this is what conciation

;

stitutes assertion or inference into a logical process. is

It

the concern of the science of logic, as contrasted with

psychology, to

criticise

such assertions and inferences

from the point of view of their validity or invalidity. Let us then consider certain mental processes particular processes

of association

— which

—

in

have the

semblance of inference. In the many unmistakeable cases of association in which no inference whatever is even apparently involved. Any first

place, there are

familiar illustration, either of contiguity or of similarity, will

prove that association in itself does not entail inIf a cloudy sky raises memory-images of a

ference.

storm, or leads to the mental rehearsal of a poem, or

suggests the appearance of a slate roof, in none of these revivals

by association

is

there involved anything in the

remotest degree resembling inference. that which

tiguity

is

involve

some sort

is

is

The case

of con-

most commonly supposed

to

of inference; but in this supposal there

a confusion between recollection and expectation.

Our

recollection of storms that

we have experienced

in

CHAPTER

4 the past

a storm

is is

I

obviously distinct from our expectation that

coming on

in the

immediate

this latter process of expectation,

future.

and not

or less properly applied

;

but even here

We

we

storm when at in

to

to the former

process of recollection, that the term inference a careful psychological distinction.

It is

more

is

we must make may expect a

notice the darkness of the sky, without

having actually recalled past experiences of storms; this case no inference is involved, since there has

all

been only one

what would constitute the conclusion without any other assertion that would assertion, namely,

In order to speak properly of

constitute a premiss.

inference in such cases, the assertion that the sky will

be a storm.

is

minimum

required

is

the

cloudy and that therefore there

Here we have two

explicit assertions,

together with the inference involved in the word 'therefore.'

It is

of course a subtle question for introspection

as to whether this threefold assertion really takes place.

This

difficulty

inference;

it

does not at

would only

all affect

our definition of

affect the question

whether

in

any given case inference had actually occurred. It has been suggested that, where there has been nothing that logic could recognise as an inference, there has yet been inference in a psychological sense; but this contention is absurd, since it is entirely upon psychological grounds that we have denied the existence of inference in

such cases.

Let us consider further the logical aspects of a genuine inference, following upon such a process of association as

we have

illustrated.

The

hold that the appearance of the sky

is

scientist

may

not such as to

warrant the expectation of an on-coming storm.

He

INFERENCE IN GENERAL

5

may, therefore, criticise the inference as invalid. Thus, assuming the actuaHty of the inference from the psychological point of view, it may yet be criticised as invalid from the logical point of view. So far we have taken the simplest case, where the single premiss 'The sky is

cloudy'

is

But,

asserted.

when an

additional premiss

such as 'In the past cloudy skies have been followed

by storm'

is

then the inference

asserted,

further

is

two premisses taken together more complete ground for the conclusion

rationalised, since the

constitute a

This additional premiss

than the single premiss. technically

thinker

is

known

as

2.

particular proposition.

pressed to find

for his conclusion,

he

assert that in all his expe-

riences cloudy skies have been followed limited universal).

The

final

by storm

stage of rationalisation

reached when the universal limited to cases

If the

stronger logical warrant

still

may

is

all

(a is

remembered

used as the ground for asserting the unlimited

is

But even now the critic may press for further justification. To pursue this topic would obviously require a complete treatment of induction, syllogism, etc., from the logical point of view. Enough has been said to show that, however inadequate may be the grounds offered in justification of a conclusion, this has no bearing upon the nature or upon universal for

all

cases.

the fact of inference as such, but only upon the criticism of

it

as valid or invalid.

As logical

in association, so also in perception, a

problem presents

itself.

There appear

psychoto

be at

least three questions in dispute regarding the nature of

perception, which have close connection with logical analysis: First,

how much

is

contained

in the

percept

CHAPTER

6

I

besides the immediate sense experience?

does perception involve assertion? involve inference?

problem,

let

To

illustrate the

us consider what

perception of a match-box.

is

This

Secondly,

does

Thirdly,

nature of the

meant by the is

it

first

visual

generally supposed

to include the representation of its tactual qualities

which case, the content of the percept includes

;

in

qualities

other than those sensationally experienced.

On

the

other hand, supposing that an object touched in the

dark

is

recognised as a match-box, through the special

character of the tactual sensations, would the represen-

match-box from other objects be included in the tactual perception of it as a match-box ? The same problem arises when we recognise a rumbling noise as indicating a cart in

tation of such visual qualities as distinguish a

the road:

i.e.

should

we

say,

in

this case, that the

auditory percept of the cart includes visual or other distinguishing characteristics of the cart not sensationally

experienced? In

my view it is

inconsistent to include in

the content of the visual percept tactual qualities not sensationally experienced, unless

we

also include in the

content of a tactual or auditory percept visual or similar qualities not sensationally experienced

in

This leads up to our second question, namely whether such perceptions there is an assertion {a) predicating

of the experienced sensation certain specific qualities; or an assertion {B) of having experienced in the past similar sensations simultaneously with the perception of ^

In speaking here of the mental representation of qualities not

sensationally experienced, I

portant psychological

am

putting entirely aside the very im-

question as to whether such mental repre-

sentations are in the form of 'sense-imagery' or of 'ideas.'

INFERENCE IN GENERAL a certain object.

we may

first

7

Employing our previous

illustration,

question whether the assertion 'There

is

a cart in the road' following upon a particular auditory sensation,

involves

of that sensation.

the

(a)

Now

if

explicit

characterisation

the specific character of the

noise as a sensation merely caused 2. visual image which in its turn

caused the assertion 'There

road,' then in the explicit inference.

is

absence of assertion In order to

a cart in the

{a) there is

become

no

inference, the

character operating (through association) as cause would

have to be predicated (in a connective judgment) as ground. On the other hand, any experience that could be described as hearing a noise of a certain more or less determinate character would involve,

in

my

opinion,

besides assimilation, a judgment or assertion {a) expres-

some such words

sible in

The is

as 'There

further assertion that there

is

is

a rumbling noise.'

a cart in the road

accounted for (through association) by previous ex-

periences of hearing such a noise simultaneously with

Assuming that association operates by arousing memory-images of these previous experiences, it is only when by their vividness or obtrusiveness these memory-images give rise to a memory -judgment, that the assertion (^) occurs. We are now in a position to seeing a

cart.

answer the third question as for, if

to the nature of perception

either the assertion of [a) alone or of {b) with (a)

occurs along with the assertion that there the road, then inference

is

is

involved; otherwise

a cart in it is

not.

Passing from the psychological to the strictly logical problem, we have to considei; in further detail § 3.

the conditions for the validity of an inference symbolised as 'p

.'

.

qJ

These conditions are

twofold,

and may be

CHAPTER

8

conveniently distinguished

in

I

accordance with

nology as constitutive and epistemic.

my termi-

They may be

briefly formulated as follows:

Conditions for Validity of the Inference 'p

(ii)

.'.

q'

Constitutive Conditions: (i) the proposition '/' and the proposition 'p would imply q^ must both be true. Epistemic Conditions: (i) the asserting of '/' and

(ii) the asserting of '/ would imply q' must both be permissible without reference to the asserting of q.

be noted that the constitutive condition exthe dependence of inferential validity upon a

It will

hibits

between the contents of premiss and of conclusion the epistemic condition, upon a certain relation between the asserting of the premiss and the asserting of the conclusion. Taking the constitutive condition first, we observe that the distinction between inference and implication is sometimes expressed by certain relation ;

calling implication 'hypothetical inference'

ing of which

is that,

must be categorically asserted implication, this premiss thetically.

— the mean-

in the act of inference, the

is

;

premiss

while, in the relation of

put forward merely hypo-

This was anticipated above by rendering

the relation of implication in the subjunctive

mood

(/ would imply ^) and the relation of inference

in the

indicative

mood

[p implies q\

Further to bring out the connection between the epistemic and the constitutive conditions,

it

must be

pointed out that an odd confusion attaches to the use of the word 'imply' in these problems. The almost universal application of the relation of implication in logic

is

as a relation

between two propositions; but, in term 'imply' is used as a relation

familiar language, the

INFERENCE IN GENERAL between two

9

Consider for instance

assertions.

(a) 'B's

asserting that there will be a thunderstorm would imply

having noticed the closeness of the atmosphere,' and (S) 'the closeness of the atmosphere would imply that there will be a thunderstorm.' The first of these relates his

two mental acts of the general nature of assertion, and is an instance of 'the asserting of ^ would imply having asserted/'; the second is a relation between two propositions, and is an instance of 'the proposition/ would imply the proposition ^.' Comparing (a) with (d) we find that implicans and implicate have changed places. Indeed the sole reason why the asserting of the thunderstorm was supposed to imply having asserted the closeness of the atmosphere was that, in the speaker's judgment, the closeness of the atmosphere would imply that there will be a thunderstorm.

Recognising, then, this double and sometimes am-

biguous use of the word 'imply,'

we may

restate the

of the two epistemic conditions and the second of

first

the two constitutive conditions for the validity of the inference

'/>

.'.

q' as follows:

Epistemic condition sition '/' should not

proposition

(i)

Constitutive condition

former

the asserting of the propo-

'^.'

imply the proposition

The

:

have implied the asserting of the

is

(ii)

:

the proposition '/' should

'^.'

merely a condensed equivalent of our

original formulation, viz. that 'the asserting of the pro-

position

'/'

must be permissible without reference

asserting of the proposition

Now

to

the

'q.'

the fact that there

is

this

double use of the

term 'imply' accounts for the paradox long

felt

as

CHAPTER

10

regards the nature of inference

I

:

for

may be

order that an inference

it is

urged

that, in

formally valid,

it

is

required that the conclusion should be contained in the

premiss or premisses; while, on the other hand,

if

there

any genuine advance in thought, the conclusion must not be contained in the premiss. This word 'contained' is doubly ambiguous: for, in order to secure formal validity, the premisses regarded as propositions must is

imply the conclusion regarded as a proposition

;

but, in

order that there shall be some real advance and not a

mere

petitio principii,

it is

required that the asserting

of the premisses should not have implied the previous

These two horns of the dilemma are exactly expressed in the constitutive and asserting of the conclusion.

epistemic conditions above formulated. § 4.

We

shall

now

explain

how

the constitutive

conditions for the validity of inference, which have been

expressed

most general form, are realised

in their

familiar cases.

would imply

The

in

general constitutive condition 'p

q' is yi?r?;^^//)/ satisfied

logical relation holds of

/

to

q-,

when some

and

it

is

specific

upon such a

relation that the formal truth of the assertion that 'p

would imply q' relations which

is

based.

will

There are two fundamental

render the inference from

/

to q,

and these relations will be expressed in formulae exhibiting what will be called the Applicative and the Implicative Principles of Inference. The former may be said to formulate what is involved in the intelligent use of the word 'every'; the latter what is involved in the intelligent use of the word 'if.' not only valid, but formally valid

;

In formulating the Applicative principle,

we

take

p

INFERENCE IN GENERAL

ii

to stand for a proposition universal in form,

and q

for

a singular proposition which predicates of

some

single

case what

The

Appli-

predicated universally in p.

is

cative principle will then be formulated as follows:

a predication about 'every'

we may

same predication about 'any

given.'

From infer the

In formulating the Implicative principle,

compound

to stand for a ''x implies

'y'

The

and q

J)/'"

formally

we take/

proposition of the form 'x and

to stand for the simple proposition

Implicative principle will then be formulated

as follows:

y

From the compound proposition we may formally infer

'x

and

''x implies

'jj/.'

We find two different forms of proposition,

§ 5.

or other of which inference;

the

is

used as a premiss

distinction

logicians.

is

funda-

controversy

In familiar logic the two kinds of

proposition to which tively as universal

much

one

every formal

between which

mental, but has been a matter of

among

in

I

known respecAs an example of

shall refer are

and hypothetical.

the former, take 'Every proposition can be subjected

from this universal proposition we 'That ''matter exists'' can be submay directly infer jected to logical criticism.' This inference illustrates to logical criticism';

what

have

I

premiss

will

called the Applicative Principle,

be called an Applicational universal.

next the example 'If this can swim

it

breathes,'

and and

can swim'; from this conjunction of propositions

'it

we

breathes'; here, the hypothetical premiss

infer that

'it

being

our terminology called implicative, the

in

its

Take

in-

ference in question illustrates the use of the Implica-

CHAPTER

12

tive Principle.

ciples that

It is

I

the combination of these two prin-

marks the advance made

in

passing from

the most elementary forms of inference to the syllogism.

For example: swim' we can

From 'Everything

breathes

infer 'This breathes

where the applicative principle only

is

if

if

able to

able to swim,'

employed. Con-

joining the conclusion thus obtained with the further

premiss 'This can swim,'

we can

infer 'this breathes,'

where the implicative principle only is employed. In which involves the interpolation of an additional proposition, we have shown how the two principles of inference are successively this analysis of the syllogism

employed.

The

would read as

ordinary formulation of the syllogism follows:

'Everything that can swim

breathes; this can swim; therefore this breathes.' place of the usual expression of the major premiss,

In I

have substituted 'Everything breathes if able to swim,' in order to show how the major premiss prepares the

way

for the inferential

employment successively of the

and of the implicative principles. the two propositions Every proposition can be subjected to logical criticism' and 'everything that is able to swim breathes' must be carefully contrasted. Both of them are universal in form; but in the

applicative § 6.

Now

latter the subject

'

term contains an

explicit characterising

The

presence of a charac-

adjective, viz. able to swim.

terising adjective in the subject anticipates the occasion

on which the question would arise whether this adjecIn the tive is to be predicated of a given object. syllogism, completed as in the preceding section, the universal major premiss is combined with an affirmative

minor premiss, where the adjective entertained

cate-

INFERENCE IN GENERAL gorically

2.?,

predicate of the minor

is

13

same

the

as that

which was entertained hypothetically as subject of the major. This double functioning of an adjective is the one fundamental characteristic of all syllogism where it will be found that one (or, in the fourth figure, every) term occurs once in the subject of a proposition, where ;

it

is

entertained hypothetically, and again in the pre-

dicate of another proposition

where

is

it

entertained

categorically.

The

between the two contrasted universals (applicational and implicational) lies in the fact that an inference can be drawn from the former on the applicative principle alone, which dispenses with the minor premiss. We have to note the nature of the essential distinction

substantive that occurs in the applicational universal as distinguished from that which occurs in the implicational universal.

position

'

The example

already given contained 'pro-

as the subject term,

and a few other examples

are necessary to establish the distinction in question.

'Every individual of the Republic of predications

is

is self-identical,'

therefore 'the author

self-identical';

'Every conjunction

is

commutative,' therefore 'the conjunc-

tion lightning before '

Every

adjective

is

and thunder after

is

commutative'

a relatively determinate specifica-

tion of a relatively indeterminate adjective,' therefore

'red

is

tively

a relatively determinate specification of a relaindeterminate

adjective.'

These

could be endlessly multiplied, in which

illustrations

we

directly

apply a universal proposition to a certain given instance. In such cases the implicative as well as the applicative principle

would have been involved

if

it

had been

necessary or possible to interpolate, as an additional

CHAPTER

14

I

datum, a categorical proposition requiring certification, to serve as minor premiss. Let us turn to our original

and examine what would have been involved if we had treated the inference as a syllogism; it would have read as follows: 'Every proposition can be subjected to logical criticism'; 'That matter exists is a proposition'; therefore 'That matter exists can be subillustration

jected to logical criticism.'

word proposition occurs premiss, and as predicate I

have to maintain

premiss

is

In this form, the substantive as subject

the universal

in

minor

that this introduction of a

is

superfluous and even misleading.

be observed

What

in the singular premiss.

that, in all the illustrations

It

should

given above of

the purely applicative principle, the subject-term in the universal premiss denotes a general category.

It

follows

from this that the proposed statement 'That matter exists is

is

a proposition

'

is

redundant as a premiss

for

it

impossible for us to understand the meaning of the

phrase 'matter exists' except so far as it

;

to denote a proposition.

In the

we understand

same way,

would

it

be impossible to understand the word 'red' without understanding it to denote an adjective and so in all other cases of the pure employment of the applicative principle. In all these cases, the minor premiss which ;

—

might be constructed is not a genuine proposition the truth of which could come up for consideration because the understanding of the subject-term of the minor demands a reference of it to the general category there predicated of it. This proposed minor premiss, therefore, is a peculiar kind of proposition which is not exactly what Mill calls 'verbal,' but rather what

meant by

'analytic,'

and which

I

propose to

call

'

Kant struc-

INFERENCE IN GENERAL

All structural statements contain as their pre-

tural.'

dicate

15

some wide logical

category, and their fundamental

impossible

to realise the

meaning of the subject-term without

implicitly con-

characteristic

is

that

it

is

under that category. The structural proposition can hardly be called verbal, because it does not depend upon any arbitrary assignment of meaning to ceiving

it

a word;

—

examples.

this point

For

being best illustrated by giving

instance, taking as subject-term

'the

'The author of the Republic wrote something,' would be verbal, while The author of the Republic is an individual,' would

author of the Republic,' then

'

be

structural.

In reality the subject of a verbal pro-

and the subject of a structural proposition are not the same; the one has for its subject the phrase 'the author of the Republic,' and the other the object denoted by the phrase. This is the true and final principle for position,

distinguishing a structural (as well as a genuinely real

or synthetic statement) from a verbal statement. § 7.

Since a category

expressed always by a

is

general substantive name, the important question arises as to whether or

how

the

'existent' or 'proposition'

name is

ordinary general substantive

to

of a category such as

name

is

be

but, so far as a category can

;

in

the

defined in terms

of determinate adjectives which constitute tion

Now

be defined.

connota-

its

be defined,

terms of adjectival determinables\

e.g.

it

ihust

an existent

what occupies some region of space or period of time the determinates corresponding to which would be, occupying some specific region of space or period of is

:

time.

Similarly,

the category

'proposition'

could be

defined by the adjectival determinable 'that to which

CHAPTER

i6

some

I

assertive attitude can be adopted,' under

which

the relative determinates would be affirmed, denied, doubted, etc.

We

may

indicate the nature of a given

category by assigning the determinables involved construction.

Using

in its

capital letters for determinables

and corresponding small letters for their determinates (distinguished amongst themselves by dashes), the major premiss of the syllogism would assume the following form Every \s p \{ m; where the determinables and serve to define the category so far as required

M

MP

:

P

for the syllogism in question.

the vague

word

Here we

'thing' previously

substitute for

employed, the symbol

MP to indicate the category of reference

;

namely, that

comprising substantives of which some determinate character under the determinables dicated.

The

Til/

and P can be pre-

statement that the given thing

redundant where

M and P

is

MP

is

are determinables to which

the given thing belongs for the thing could not be given ;

an act of construction except so far as it was given under the category defined by these determinables. Hence any genuine act of characterisation of the thing so given would consist in giving to either immediately or in

these mere determinables a comparatively determinate

For example,

value.

thing

is

it

MP, we may

being assumed that the given characterise

it

in

such determi-

nate forms as 'm and/*,' 'm or/,' 'p \i m,' 'not both/> and m' where the predication of the relative determinates m and / would presuppose that the object had been constructed under MP. In defining the function of a proposition to be to characterise relatively determinately what is given to be characterised, we now see that what is 'given is not given in a merely abstract

INFERENCE IN GENERAL sense, but

—

in

being given

17

—the determinables which

have to be determined are already presupposed. § 8.

We

may now show more

clearly

why

the force

from that of the term if and how, in the syllogism, the two corresponding principles of inference are both involved. The major

of the term 'every'

distinct

is

*

;

premiss having been formulated

minables

M and P,

in

terms of the deter-

the whole argument will assume

the following form

Every

{a)

from which we

MP is/ infer,

The given

[b)

m,

if

by the applicative principle alone is/ if m.

MP

Next we introduce the minor,

The given

{c)

and

finally infer,

{d)

Now

if

MP

viz.

is m,,

by the implicative principle alone:

The given MP'isp. we held that the inference from

{a) to {b) re-

quired the implicative principle as well as the applicative,

'The given thing is MP' the syllogism would assume the

so that a minor premiss

must be interpolated, following [a)

more complicated form:

Everything

is

/

\{

m

if

is

/

MP (the

reformulated

major). .'.

{b)

The

given thing

if

;^

if

MP

(by the

applicative principle alone).

Next we introduce {c) .'.

{d)

The The

as minor

given thing given thing

is is

MP. / if w

(by the implicative

principle alone); finally, (e) .'.

(/)

introducing the original minor,

The given The given

thing thing

is is

viz.

m.

/

(by the implicative prin-

ciple alone). J. L. II

2

CHAPTER

i8

Now

this

I

lengthened analysis of the syllogism, while

involving the implicative principle twice, involves as well as the applicative principle the introduction of a

new

MP,

which hints at the doubt whether what is given is given as MP. But if this were a reasonable matter of doubt requiring explicit affirmation, on the same principle we might doubt whether what is given is a 'thing,' in some more minor, viz, that the given thing

generic sense of the word 'thing.' mitted, the syllogism

is

is

If this

doubt be ad-

resolved into three uses of the

implicative principle, with two extra minor premisses.

Such a resolution would in fact lead by an infinite regress to an infinite number of employments of the implicative principle. To avoid the infinite regress we must establish some principle for determining the point at which an additional minor is not required. The view then that I hold is not merely that what is given is a 'thing' in the widest sense of the term thing, but that

what

is

given

is

always given as demanding to be

characterised in certain definite respects size,

—

e.g. colour,

MP'

—

and that 'The given thing is

weight; or cognition, feeling, conation

therefore such a proposition as

presupposed in its being given, i.e. in being given as requiring determination with respect and P. The above to these definite determinables syllogism which the is resolved formulation, therefore, in is

given,

it is

M

into a process involving the applicative

cative principles each only once, for

it

is

and the impli-

logically justified;

brings out the distinction between the function of

employment of the and the function of if as

the term every as leading to the applicative principle alone,

leading to the employment of the implicative principle

INFERENCE IN GENERAL

19

and furthermore it distinguishes between the process in inference which requires the applicative principle alone from that which requires the implicative as alone;

well as the applicative principle.

The

between the cases

distinction

in

which the im-

or cannot be dispensed with whether depends, so upon the subject-term of the universal stands for a logical category or not. But we may go further and say that, even if the subject of the plicative principle can far,

universal

is

not a logical category, provided that

it

is

definable by certain determinates, and that the subject

of the conclusion

is

only apprehensible under those

determinables, then again the use of the implicative principle

may be

For example:

dispensed with.

'All

material bodies attract; therefore, the earth attracts.'

Here the term

'material body'

category in that

it

is

of the nature of a

can only be defined under such de-

terminables as 'continuing to exist' and 'occupying some region of space'

;

furthermore the earth

is

constructively

given under these determinables: hence a proposed

minor premiss to the

body

is

superfluous,

effect that the earth is

a material

and the above inference involves

only the applicative principle. Again 'All volitional acts are causally determined; therefore, Socrates' drinking

of hemlock was causally determined.'

of the conclusion

is

Here the

subject

constructively given under the de-

terminables involved in the definition of volitional

which again alone.

gate

is

justifies the

use of the applicative principle

As a third example less

act,

' :

Every denumerable aggre-

than some other aggregate: therefore, an

aggregate whose number

is

5resup/>oses it, in same way as a proposition presupposes the understanding of the meaning of the terms involved identity,

just the

without asserting such meaning. 8

10.

We

have discussed the case

in

which a minor

INFERENCE IN GENERAL

21

may be dispensed with, namely that in which a certain mode of using the applicative principle is premiss

without the employment of the implicative.

sufficient

We

now

will

turn to a complementary discussion of the

case in which there

is

unnecessary employment of the

by the insertion of what may be called a redundant major premiss. It will be convenient to call the redundant minor premiss a subminor, and the redundant major premiss to which we applicative principle, entailed

shall

now

turn

—a

—

super-major.

In this connection

I

shall introduce the notion of a formal principle of in-

ference,

which

will apply, not

strictly formal,

only to inferences that are

but also to inferences of an inductive

nature, for which the principle has not at present been finally

formulated and must therefore be here expressed

without qualifying

detail.

The

discussion will deal with

cases in which the relation of premiss or premisses to

conclusion

is

such that the inference exhibits a formal

principle.

We

the point first by taking the and next, the ultimate (but as yet

shall illustrate

principle of syllogism,

unformulated) principle of induction. syllogism, taking

/

and q

As

to represent

regards the

the premisses

and r the conclusion, we may say that the

syllogistic

principle asserts that provided a certain relation holds

between the three propositions p, q, and r, inference from the premisses p and q alone will formally justify the conclusion r. Now it might be supposed that this syllogistic principle constitutes in a sense an additional premiss which, when joined with p and q, will yield a more complete analysis of the syllogistic procedure. But on consideration it will be seen that there is a sort

CHAPTER

22

I

of contradiction in taking this view: for the syllogistic principle asserts that the premisses

/

and q are alone

sufficient for the formal validity of the inference, so that, if

the principle

is

inserted as an additional premiss co-

ordinate with

/

contradicted.

In illustration

and

q,

the principle itself

we

will

is

virtually

formulate the syllo-

gistic principle:

to

'What can be predicated of every member of a class, which a given object is known to belong, can be pre-

dicated of that object.'

Now, taking a

specific syllogism:

'Every labiate .'.

if

we

The The

is

dead-nettle dead-nettle

square-stalked, a labiate, is square-stalked,'

is

inserted the above-formulated principle as a pre-

miss, co-ordinate with the

two given premisses, with a

view to strengthening the validity of the conclusion, this would entail a contradiction because the principle ;

claims that the two premisses are alone sufficient to justify the conclusion

Now

the

same

'The dead-nettle

is

square-stalked.'

holds, mutatis mutandis, of

any pro-

posed ultimate inductive principle. Here the premisses but as many, and summed up not as two

are counted in

—

—

the single proposition 'All examined instances charac-

by a certain adjective are characterised by a certain other adjective'; and the conclusion asserted terised

(with a higher or lower degree of probability) predicates of all

what was predicated

all exam,ined.

Now, in accordance with the inductive summary premiss is sufficient for asserting

principle, the

in

the premiss of

the unlimited universal (with a higher or lower degree

of probability).

To

insert this principle, as

an additional

INFERENCE IN GENERAL

23

premiss co-ordinate with the summary premiss, would, therefore, virtually involve a contradiction. tion,

we

will

In illustra-

roughly formulate the inductive principle

'What can be predicated of all examined members of a class can be predicated, with a higher or lower degree of probability, of all members of the class.'

Now, taking a

specific inductive inference:

'All examined swans are white. .'. With a hig-her or lower degree of probability, all swans are white,' if

we

inserted the above-formulated inductive principle

as a premiss, co-ordinate with the

summary premiss

examined swans are

view to strengthening

white,' with a

'All

the validity of the conclusion, this would entail a contradiction

premiss

because the principle claims thatthis summary

;

alone

is

sufificient to justify

the conclusion that

'With a higher or lower degree of probability,

all

swans

are white.'

We

may

principle

shortly express the distinction between a and a premiss by saying that we draw the

conclusion

from

the premisses in accordance with (or

through) the principle.

In other words,

we immediately

see that the relation amongst the premisses and conclusion

is

principle,

a specific case of the relation expressed in the

and hence the function of the

principle

is

stand as a universal to the specific inference as an stance of that universal to

:

where the

be inferred from the former

(if

latter

there

is

may be

to in-

said

any genuine

Supreme Applicative from x =y and y = z, we may

inference) in accordance with the principle. infer

x = z.

For example

:

This form of inference

is

expressed, in

general terms, in the Principle: 'Things that are equal to the

same thing are equal

to

one another.' Now, here,

CHAPTER

24

x^y 2indy = 2—are alone

the two premisses for the conclusion

/rom

I

x = 2;

sufficient

the conclusion being

drawn

the two premisses through or in accordance with

the principle which states that the two premisses are

a/one sufficient to secure validity for the conclusion.

The

principle cannot therefore be

added co-ordinately Moreover the

to the premisses without contradiction.

above-formulated principle (which expresses the transitive

property of the relation of equality) cannot be

subsumed under the

way

syllogistic principle.

In the

same

the syllogistic or inductive principle

may be

called

a redundant or super-major, because

it

introduces a mis-

leading or dispensable employment of the applicative principle. § II.

There

is

a special purpose in taking the in-

ductive and syllogistic principles in illustration of super-

many

have maintained that any does not rest on an independent principle, but upon the syllogistic principle itself; in other words, they have taken syllogism to exhibit the sole form of valid inference, to which any majors, for

logicians

specific inductive inference

other inferential processes are subordinate.

Now

it

is

true that the inductive principle could be put at the

head of any

specific inductive inference,

and thus be

related to the specific conclusion as the major premiss

of a syllogism

is

related to

its

conclusion

could be said of the syllogistic principle

:

;

but the same

namely that

it

could be put at the head of any specific syllogistic inference to which

it

is

related in the

major premiss of a syllogism But,

if

we

is

same way

related to

its

as the

conclusion.

are further to justify the specific inductive

inference by introducing the inductive principle, then,

INFERENCE IN GENERAL by

parity of reasoning,

we should have

25

to introduce the

syllogistic principle further to justify the specific syllogistic inference.

would lead tration

will

But

in the case of the

syllogism this

to an infinite regress as the following illus-

show.

Thus, taking again as a specific

syllogism, that

from (/) 'All labiates are square-stalked'

and

we may

(^)

infer (r)

adding to principle, namely and,

'The dead-nettle 'The dead-nettle this

as

is is

a labiate' square-stalked,'

super-major the syllogistic

(a), we have the following argument For every case o( Af, of 6" and ofP: the inference 'every Jkf is P, and kS" is Af, .-. S is P' is valid. (d) The above specific syllogism is a case of (a).

(a)

(c)

.'.

The

specific syllogism

is

valid.

But here, in inferring from (a) and (d) together to (c), we are employing the syllogistic principle, which must stand therefore as a super-major to the inference from (a) and (d) together to (c), and therefore as super-supermajor to the specific inference from/ and ^ to r. This would obviously lead to an infinite regress. We may show that a similar infinite regress would be involved if we introduced, as super-major, the inductive principle, by the following illustration. Taking again as a specific inductive inference that from 'All examined swans are white' we may infer with a higher All swans are or lower degree of probability that white'; and adding to this as super-major the inductive principle, namely (a), we have the following '

arg-ument: (a) For every case of Af and of P: from 'e veryexamined Af Is P,' we may infer, with a higher or lower degree of probability, that 'every Af is P';

CHAPTER

26

I

The above specific induction is a case of (a), .'. The specific induction is valid. here we may argue in regard to this (a), (d), {c)

{b) (c)

But,

as

Thus, by introducing the inductive principle as a redundant major premiss, we shall be led as before, by an infinite regress, in the case of the

to a repeated

previous

employment

(a), (d),

(c).

of the syllogistic principle.

This whole discussion forces us to regard the inductive and syllogistic principles as independent of one another, the former not being capable of subordination to the latter; for

we cannot

in

any way deduce the

ductive principle from the syllogistic principle.

who have regarded

in-

Those

the syllogistic principle as ultimately

in fact arrived at this conclusion by noting shown above, the inductive principle could be introduced as a major for any specific inductive inference, in which case the inference would assume the syllogistic form {a\ (d), (c). But this in no way affects the supremacy

supreme, have that, as

of the inductive principle as independent of the syllogistic.

CHAPTER

II

THE RELATIONS OF SUB-ORDINATION AND CO-ORDINATION AMONGST PROPOSITIONS OF DIFFERENT TYPES § I.

In the previous chapter

we have shown

that the

syllogism which establishes material conclusions from material premisses involves the alternate use of the

Applicative and Implicative principles. principles, its

Now these

two

which control the procedure of deduction

in

widest application, are required not only for material

inferences, but also for the process of establishing the

formulae that constitute the body of logically certified theorems.

All these formulae are derived from certain

intuitively

evident axioms which

may be

explicitly

be found that the procedure of deducing further formulae from these axioms requires enumerated.

It

will

only the use of the Applicative and Implicative principles

;

these, therefore, cover a wider range than that

But a final question remains, as to how the formal axioms are themselves established in their universal form. By most formal logicians it is assumed that these axioms are presented immediately as self-evident in their absolutely universal form but such a process of intuition as is thereby assumed is really the result of a certain development of the reasoning of mere syllogism.

;

powers. is

Prior to such development,

I

hold that there

a species of induction involved in grasping axioms in

their absolute generality

and

in

conceiving of form as

CHAPTER

28

II

constant in the infinite multiplicity of cations.

We

its

possible appli-

therefore conclude that behind the axioms

there are involved certain supreme principles which bear to the Applicative

and Implicative principles the same

relation as induction in general bears to deduction

;

and,

even more precisely, that these two new principles may be regarded as inverse to the Applicative and Implicative principles respectively. This being so, it will be convenient to denominate them respectively. Counterapplicative andCounter-implicative. It should bepointed

out that whereas the Applicative and Implicative principles hold for material as well as formal

procedure,

Counter-principles

the

are

inferential

used for the

establishment of the primitive axioms themselves upon

which the formal system

is

based.

We

will

then pro-

ceed to formulate the Counter-principles, each in immediate connection with § 2.

The

its

corresponding direct principle.

Applicative principle

is

that which justifies

the procedure of passing from the asserting of a predication about

'

every

'

to the asserting of the

predication about 'any given.'

same

Corresponding to this, may be formulated:

the Counter-applicative principle

'When we are justified in passing from the asserting of a predication about some one given to the asserting of the same predication about some other, then we are also justified in asserting the same predication about every.

Roughly the Applicative from

justifies

principle justifies

inference

and the Counter-applicative inference from 'any' to 'every'; but whereas

'every'

to

'any,'

the former principle can be applied universally, the latter holds only in certain

narrowly limited cases; and.

SUB-ORDINATION AMONGST PROPOSITIONS in

particular,

for the

formulae of Logic. those in which

and

we

establishment of the primitive

These cases may be described as see the universal in the particular,

kind of inference

this

duction,' because

which we

29

it is

will

be called 'intuitive

in-

that species of generalisation in

intuite the truth of a universal proposition in

the very act of intuiting the truth of a single instanced

Since intuitive induction

is

of course not possible in

every case of generalisation,

we have

implied in our

formulation of the principle that the passing from 'any' to 'every'

is

justified only

one' to 'any other'

when

the passing from 'any

Now there

is justified.

are forms of

we can pass immediately from any one given case to any other if it were not so, the principle would be empty. For instance, we may illustrate the Applicative principle by taking the formula: 'For every value of/ and of ^, "/ and q' would imply "/",' from which we should infer that 'thunder and lightning' would imply 'thunder.' If now we enquire inference in which

;

how we oi

p

will

are justified in asserting that for every value

and of

q,

'p

and

q'

would imply

'/,'

the answer

supply an illustration of the Counter-applicative

principle.

Thus,

in asserting that

ning" would imply "thunder"'

'"thunder and light-

we

see that

we could

proceed to assert that '"blue and hard" would imply

and in the same act, that "/ and (7" would imply "/" for all values of/ and of ^.' The second inverse principle to be considered is § 3. "blue",'

'

Before discussing this inverse

the Counter-implicative. principle, ^

This

is

it

will

be necessary to examine closely the

a special case of

'

intuitive induction,' the

uses of which will be examined in Chapter VIII.

more general

CHAPTER

30

Implicative principle

formulated:

'Given

itself,

II

which may be provisionally

that a certain proposition

would

we can

validly

formally imply a certain other proposition,

latter from the former.' Now we one positive element in the notion of

proceed to infer the find that the

formal implication inference,

is its

equivalence to potentially valid

and that there

is

no single relation properly

called the relation of implication.

We

must therefore

bring out the precise significance of the Implicative

by the following reformulation: 'There are relations such that, when one or other of these subsists between two propositions, we may validly infer the one from the other.' From the principle

certain specifiable

enunciation of this principle

we can

to the enunciation of its inverse

pass immediately

— the Counter-implica-

tive principle

'When we have

inferred, with a consciousness of

some proposition from some given premiss or premisses, then we are in a position to realise the specific validity,

form of relation that subsists between premiss and conclusion upon which the felt validity of the inference depends.'

Here, as

in the case of the Counter-applicative principle,

we must

point out that there are cases in which

tuitively recognise the validity of inferring

we

in-

some con-

crete conclusion from a concrete premiss, before having

recognised the special type of relation of premiss to conclusion which renders the specific inference valid

otherwise the Counter-implicative principle would be

empty.

In illustration,

we will

trace back

some accepted

relation of premiss to conclusion, upon which the validity

of inferring the one from the other depends; and this

SUB-ORDINATION AMONGST PROPOSITIONS will entail reference to a preliminary

procedure

31

in ac-

cordance with the Counter-applicative principle;

for

every logical formula is implicitly universal. Thus we might infer, with a sense of validity from the information

'Some Mongols

are Europeans' and from this

alone, the conclusion

We

'Some Europeans

datum

are Mongols.'

proceed next in accordance with the Counter-appli-

cative principle to the generalisation that the inference

M

from 'Some

we

Finally

\s

P'

'Some

to

P

is

M'

is

always

valid.

are led, in accordance with the Counter-

implicative principle, to the conclusion that

it is

the re-

lation of 'converse particular affirmatives' that renders

the inference from

'Some

M

P'

is

to

'Some

P

is

M'

valid,

We

§ 4.

have regarded the

intuition underlying the

Counter-applicative principle as an instance of 'seeing

the universal in the particular'; and correspondingly the intuition underlying the Counter-implicative principle

may be regarded as an instance of 'abstracting a common But the dii'ect types of intuition operate over a much wider field than the Counter-applicative and Counter-implicative principles for, whereas form

in

diverse matter.'

:

the twin inverse principles operate only in the estab-

lishment

of

axioms,

the

form. plicitly

These

types

direct

are involved wherever there

is

of

intuition

either universality or

have been exstill more nature of the procedure conducted in

direct types of intuition

recognised by philosophers

purely intuitive

;

but the

accordance with the twin inverse principles accounts for the fact that these principles have hitherto not been

formulated by logicians.

Moreover the point of view

from which the inverse principles have been described

CHAPTER

32

and analysed

II

purely epistemic,

is

and the epistemic

aspect of logical problems has generally been ignored or explicitly rejected by logicians.

It

follows also from

their epistemic character that these principles, unlike

the Applicative and Implicative principles of inference,

cannot be formulated with the precision required for a purely mechanical or blind application. § 5. is

The

operation of these four supreme principles

best exhibited

by means of a scheme which comprises

propositions of every type in their relations of super-, or co-ordination to one another.

sub-,

We

propose,

therefore, to devote the remainder of this chapter to

the construction and elucidation of such a scheme. I.

Superordinate Principles of Inference. la. The Counter-applicative and Counter-implicative.

The

Id.

Applicative and Implicative.

Forrmdae:

i.e. formally certified propositions expressible in terms of variables having general

II.

application.

11^.

\\b.

III.

formulae (or axioms) derived from II I ^ in accordance with \a.

Primitive directly

Formulae successively derived from means of I b.

1 1

^ by

Formally Certified Propositions expressed in

terms having fixed application. \\\a. Those from which \\a are derived by use of the principles \a. \\\b.

Those which are derived from of the Applicative principle

I

V.

IId, (f>c, where (fya, x is not due to the nature of (^ as a function, but to the nature of the symbol x itself; that is to say, (ftx am-

—

—

biguously denotes

cjya,

biguously denotes

a, b, c, etc.

(j>b,

(f)C,

etc.,

only because

x am-

In short a propositional

function has ambiguous denotation,

if it

contains a term

having ambiguous denotation; whereas a propositional

unambiguous denotation, term having ambiguous denotation. function has

§

15.

if it

contains no

Hitherto, in illustrating Russell's account,

we

have taken the propositional function to be a function of a single variable, viz., of the symbol for the subject of the proposition, the predicate standing for a constant. It is obvious, however, that no proposition can be regarded as a function of a single variant unless the proposition is represented by a simple letter; and we will therefore take the specific propositional form 'x \s p' to illustrate a function of two variables. The variants of which this is a function would naturally be taken as the

CHAPfER

74

symbols

x and p

themselves

III

but, since Russell refuses

;

by

to allow a predicate or adjective to stand

takes as the two variables the subject term

with the symbolic variable 'x pression 'x is/'

may be

read

is

meant that instead of the

is

p,'

we suppose

leaving a blank.

if

we ought

subject-term,

we

in

together

symbolic ex-

';i:-blank is

/'; by which

full

propositional form 'x

x

is

omitted,

use a blank symbol for the

consistency to be allowed to

use a similar blank symbol for the predicate term.

would give the

same

nine combinations

rise to

propositional form: 'this

'this is/,' '^is hurt,' 'this

and

finally 'x is p.'

only 'this

is hurt,'

Of 'x

is

he

The

p.'

vs,

that the subject-term

But,

x

itself,

isjzJ*,'

all

This

of which are of

is hurt,'

'x

is

hurt,'

'^is/,' ^x is/,' 'x is/,'

these nine phrases, Russell uses

and 'x is hurt'; of which the two admittedly different

hurt'

the two latter illustrate meanings or applications of the general notion of the propositional function. Now, though

CHAPTER

82

some and denied by other

IV

philosophers,

the

together constitute an antilogism having the same

three illus-

trative value as our previous example.

Taking,

P

first,

and

Q

as asserted premisses

not-^ as conclusion, we obtain the

.*.

and

syllogistic inference

P.

All possible objects of thought have been sensationally impressed upon us;

Q.

Substance

not-i?.

is

a possible object of thought;

Substance has been sensationally impressed

upon

us.

With some explanations and

modifications this syllo-

gism represents roughly one aspect of the new

realistic

philosophy.

P

R

Taking, next, and as asserted premisses and not-^ as conclusion, we have P.

R.

All possible objects of thought have been sensationally impressed upon us;

Substance has not been sensationally impressed

upon .

•.

not-^.

us;

Substance

is

not a possible object of thought.

This syllogism represents very

fairly

the position of

Hume. Taking,

lastly,

R and Q as

not-/* as conclusion,

asserted premisses

and

we have

R. Substance has not been sensationally impressed upon us; Q. .

'.

Substance

is

a possible object of thought;

Not every possible object of thought has been sensationally impressed upon us.

not-/*.

This syllogism represents almost precisely the wellknown position of Kant.

THE CATEGORICAL SYLLOGISM As

83

our previous example these three syllogisms

in

are respectively in figures

i, 2,

and

3; and,

moreover,

Kant's argument in figure 3 has both a destructive function in upsetting Hume's position; and a constructive

function in suggesting

replacement of the

the

by a limited universal which would

particular conclusion

assign the further characteristic required for discrimi-

nating those objects of thought which have not been

obtained by experience from those which have been thus obtained. §

6.

Since the

dicta,

as formulated above, apply

only where two of the propositions are singular or instantial, they must be reformulated so as to apply also where all the propositions are general, i.e. universal or

particular.

Furthermore, they

determine directly figure.

As

all

will

be adapted so as to

the possible variations for each

follows:

Dictum for Fig. i if Every one of a

C

certain class possesses (or lacks) a certain property and Certain objects S are included in that class C, then These objects S must possess (or lack) that property P.

P

Dictum for Fig. 2 if Every one of a

certain class C possesses (or lacks) a certain property and Certain objects 6" lack (or possess) that property/*, then These objects 6" must be excluded from the

P

class C.

Dictum, for Fig. 3 if Certain objects perty

.S

possess (or lack) a certain pro-

P

6—2

CHAPTER

84

IV

and These objects ^ are included in a certain class C Not every one of the class C lacks (or possesses)

then

i.e.

that property P. Some of the class

C

possess (or lack) that pro-

perty P. In each of these dicta the word 'objects,' symbolised as S, represents the term that stands as subject in both its

occurrences; the word 'property' P, the term that

stands as predicate in both

word 'class' C, and again as

its

occurrences; and the

that term which occurs once as subject

Hence, using the symbols

predicate.

S, C, P, the first three figures are thus schematised I

Fig. 2

Fig. 3

C-P S-C S-P

C-P S-P S-C

S-P S-C C-P

Fig.

.-.

§ 7.

.-.

In order systematically to establish the

which are valid should be noted

S—P

.-.

is

in in

accordance with the above

moods dicta,

it

each figure (i) that the proposition

unrestricted

as

regards

both quality and

S—C

quantity; (2) that the proposition is independently fixed in quality, but determined in quantity by

the quantity of the unrestricted proposition the proposition

;

and

C — P\s, independently fixed in

(3) that

quantity,

but determined in quality by the quality of the unrestricted

proposition.

conclusion

is

Thus

unrestricted, the

in

Fig.

i,

minor premiss

while is

the

indepen-

dently fixed in quality but determined in quantity by the quantity of the conclusion; and the major premiss is

independently fixed

quality

in

quantity but determined in

by the quality of the conclusion.

while the minor premiss

is

In Fig.

2,

unrestricted, the conclusion

THE CATEGORICAL SYLLOGISM is

independently fixed

85

quality but determined in

in

quantity by the quantity of the minor premiss

;

and the

major premiss is independently fixed in quantity, but determined in quality by the quality of the minor preIn Fig.

miss.

3,

while the major premiss

the minor premiss

determined

is

is

unrestricted,

independently fixed in quality but

in quantity

by the quantity of the major

premiss, and the conclusion

is

independently fixed in

quantity but determined in quality by the quality of the

major premiss.

Having

in the

each case which

which or

is

/or

Fig.

2,

is

above dicta

is

phrase in

directly restrictive, the proposition

unrestricted,

O,

italicised the

may be

i.e.

of the form

seen to be: in Fig.

the minor premiss

or

B

the conclusion; in

1,

in Fig. 3, the

;

A

major premiss.

Hence each of these figures contains four fundamental moods derived respectively by giving to the unrestricted proposition the form A, E, I or O. Besides these four fundamental moods there are also supernumerary moods. These are obtained by substituting, in the conclusion, a particular for a universal;

or, in

a universal for a particular; universal for a particular.

or, in

the minor premiss, the major again, a

These supernumerary moods

be said respectively to contain a weakened conclusion, a strengthened minor, or a strengthened will

major; and, in the scheme given the propositions thus

the next section,

weakened or strengthened

be indicated by the raised

may

in

letters

w

or

.$•

will

as the case

be.

§ 8.

Adopting the method above explained, we may

now

formulate the special rules for determining the

valid

moods

in

each figure as follows

CHAPTER

86

Rules for Fig.

The quality

IV

i

conclusion being unrestricted in regard both to

and quantity,

The major

{a)

versal,

and

premiss must in quality agree

in quantity be uniwith the conclusion.

The minor premiss must be

{b)

tive,

and

in

in quality affirma-

quantity as wide as the conclusion.

Rules for Fig. 2. The minor premiss being unrestricted to quality (a)

The major versal,

[b)

The and

and

to quantity

premiss must be in quantity uniopposed to the minor.

conclusion must be in quality negative, narrow as the minor.

in quantity as

and

The and

[b)

in

regard both

quality,

conclusion must in quantity be particular, agree with the major,

in quality

The minor premiss must tive,

and

Italicising in

we may

regard both

in quality

Rules for Fig. 3. The major premiss being unrestricted

(a)

in

and quantity,

in

in quality be affirmaquantity overlap^ the major.

each case the unrestricted proposition,

moods

represent the valid

for the first three

figures in the following table:

Valid Moods for the

"

One-Class " Figures.

Fundamentals Fig.

AA^

Fig. 2

E^E

Fig. 3

AW

^

is

I

EA^

The minor and major

universal^ not otherwise.

AI/

will necessarily

overlap

if

one or the other

THE CATEGORICAL SYLLOGISM Having

§ 9.

d>7

moods of the first antilogism, we proceed to

established the valid

three figures from a single

construct those of the fourth figure also from a single

antilogism; thus:

Taking any three

classes,

it is

impossible that

The first should be wholly included in the second The second is wholly excluded from the third and The third is partly included in the first. The validity of this antilogism is most naturally

while

realised

by representing

a representation

is

classes as closed figures.

in fact valid,

Such

although the relation

of inclusion and exclusion of classes

with the logical relations expressed negative propositions respectively;

is

not identical

in affirmative for,

there

is

and

a true

analogy between the relations between classes and the

between closed

relations

between the

figures; in that the relations

relations of classes are identical with the

corresponding relations between the relations of closed

Thus adopting

figures.

as the

scheme of the fourth

figure

the above antilogism will be thus symbolised It is

impossible to conjoin the following three pro-

positions

:

P.

Every

C^

Q.

No

is

R.

Some

C2

C^

is C^,

C3, is C,.

This yields the three fundamental syllogisms (i)

If

/'and Q, then not-^?; i.e. if Every C^ is C^ and then

No No

C2

is C^,

C

is

C-

CHAPTER

88 If

(2)

Q

IV

and R, then not-P; if

No

C2

and Some C^

i.e.

C3

is

is C^,

then Not every C^ If 7?

(3)

and P, then not-^ if

Some

C^

Since the propositions

arranged

C

Some

Cj

C,

is is

of

C„.

i.e.

;

is

and Every C^ then

is

C3.

syllogisms

these

in canonical order, the valid

fourth figure can be at once written

down

moods

are

in the

ABE, B/0,

:

Moreover, since the conclusion of the first mood it may be weakened; since the minor of the second is particular, it may be strengthened; and since the major of the third is particular, it also may be

lAI. is

universal,

This yields:

strengthened.

Valid Moods of the Fourth Figure. Fundamentals

Supernumeraries \v

AEE

EIO

AEO

lAI

s

Here each supernumerary can only be one sense,

AAI

interpreted in

as containing respectively a

viz.,

s

EAO

weakened

conclusion, a strengthened minor, and a strengthened

major.

In contrast to

this,

the supernumeraries of the

first and second figures must be interpreted as containing either a weakened conclusion or a strengthened

and those of the third figure as containing either a strengthened major or a strengthened minor, minor;

§"10.

An

antiquated prejudice has long existed

against the inclusion of the fourth figure in logical doctrine,

and

in

support of this view the ground that

has been most frequently urged

is

as follows:

THE CATEGORICAL SYLLOGISM

Any argument worthy

89

of logical recognition must

be such as would occur in ordinary discourse. Now it will be found that no argument occurring in ordinary discourse is in the fourth figure. Hence, no argument in the fourth figure is worthy of logical recognition. This argument, being in the fourth figure, refutes itself; and therefore needs to be no further discussed. §

1

Having formulated

1.

certain intuitively evident

observance of which secures the validity of

dicta, the

the syllogisms established by their means,

we

will pro-

ceed to formulate equally intuitive rules the violation will render syllogisms invalid. These rules

of which will

be found to rest upon a single fundamental conour data or premisses refer to some no conclusion can be validly drawn to all members of that class. This is

sideration, viz.

only of a

which

if

class,

refers

technically expressed in the rule: (i)

'No term which

may be

undistributed in

is

its

premiss

distributed in the conclusion.'

This rule alone but from

validity,

is

not sufficient directly to secure

it

we can deduce

other directly

applicable rules which, taken in conjunction with the first, will

be sufficient to establish directly the invalidity

of any invalid form of syllogism.

we

deducinof these other rules

shall

In the course of

make

use of certain

from their emdeductive process, of which the follow-

logical intuitions that are obvious apart

ployment in this ing may be mentioned: {a) that if a term proposition,

proposition

it ;

will

distributed in any given

is

be undistributed

and conversely,

in a given proposition,

it

if

will

in

the contradictory

a term

is

undistributed

be distributed

in

the

CHAPTER

90

IV

That this

contradictory proposition.

is

so

is

directly seen

grounds that only when it has been accepted on universals distribute the subject term, and only negaproposition is tives the predicate term; and that an contradicted by an O, and an / proposition by an E. (3) That any syllogism can be expressed as an antilogism and conversely. This principle follows from the intuitive apprehension of the relation between imintuitive

A

and disjunction.

plication

That

{c)

tuition

is

formally possible for any three

is

it

terms to coincide

(This particular in-

in extension.

employed

the rejection of only one form of

in

syllogism.)

We

now

are

original principle,

{b\ and

{c),

a

in

position

from rule

i.e.

to

deduce from our

by means of {a)y application of which

(i),

other rules, the direct

exclude any invalid forms of syllogism.

will

(2)

'The middle term must be distributed

in

one or

other of the premisses.'

To

establish

which disjoins P,

this,

Q

to the syllogism 'If

the syllogism 'l[ first

of these,

if

P

us consider the antilogism

let

and

7?; this,

by

{b) is

equivalent

P and

Q, then not-7?' and also to and P, then not-^.' Taking the

a term

X

is

undistributed in the premiss

must be undistributed in the conclusion not-7?, must, by (a), be distributed in P. Applying this result to the second syllogism If P and P, then not-^,' we have shown that if the middle term is undistributed in the premiss P, it must be distributed in the premiss P. This then establishes rule (2). (3) 'If both premisses are negative, no conclusion

P,

it

i.e. it

'

X

can be syllogistically inferred.'

THE CATEGORICAL SYLLOGISM

91

For, taking any two universal negative premisses,

these can be converted

and

'

No 5

is

J/'

;

(if

necessary) into

*

No

/*

is

M'

which, by obversion, are respectively

equivalent to 'All

P

non-J/' and 'All

is

5

is

non-J/,'

which the new middle term non-J/ is undistributed But this breaks rule (2). What in both premisses. holds of two universals will hold a fortiori if one or other of the two negative premisses is particular. Thus in

rule (3)

is

established.

'A negative premiss requires a negative con-

(4)

clusion.'

For, taking again the antilogism which disjoins P, and R, this is equivalent both to the syllogism 'If/* and R, then not-^,' and to the syllogism '\{ P and Q, then not-/?.' Taking the first of these two syllogisms, by rule (3), if the premiss P is negative, the premiss R must be affirmative. Applying this result to the second

Q

syllogism,

we

have,

if

the premiss

P

conclusion not-/? must be negative.

is

negative, the

This establishes

rule (4). (5)

'A negative conclusion requires a negative

premiss.'

This

is

equivalent to the statement that two affirma-

tive premisses cannot yield a negative conclusion.

establish this rule,

we must

To

take the several different

figures of syllogism Fig.

Fig. 1

I

Fig. 3

Fig. 4

M-P S-M

P-M S-M

M-P M-S

P-M M-S

S-P

S-P

S-P

S-P

For the

first

or third figure, affirmative premisses

with negative conclusion would entail false distribution

CHAPTER

92

IV

which has been forbidden under our fundamental rule (i). Taking next the second figure, it would entail false distribution of the middle term, forbidden by rule (2), Finally taking the fourth figure,

of the major term

;

would either entail some false distribution forbidden by rules (i) and (2); or else yield the mood ^4^0 which would constitute a denial that three terms could coincide in extension, thus contravening (c). This establishes it

rule (5).

The five rules thus established may be resummed up into two rules of quality and

§ 12.

arranged and

two

rules of distribution, viz.

A. Rules of Quality. (^1)

(«o)

For an affirmative conclusion both premisses must be affirmative. For a negative conclusion the two premisses must be opposed in quality.

Rules of Distribution.

B.

{b^

The middle term must be least

(4)

distributed in at

one of the premisses.

No

term undistributed in its premiss distributed in the conclusion.

may be

These rules having been framed with the purpose of rejecting invalid syllogisms,

we may

first

point out that,

irrespective of validity, there are sixty-four abstractly

possible combinations of major, minor

The Rules

and conclusion.

of Quality enable us to reject en bloc

moods except those coming under the following heads, viz. those which contain (requiring

clusion

minor)

;

(ii)

affirmative

(i)

all

three

an affirmative con-

major and affirmative

a negative major (requiring affirmative

THE CATEGORICAL SYLLOGISM

93

minor and negative conclusion); (iii) a negative minor (requiring affirmative major and negative conclusion). This leads to the following table, which exhibits the 24 possibly valid moods unrejected by the Rules of Quality.

CHAPTER

94 /

Fig. clusion

Fig. ,

One

2.

must

premiss must be negative;

i.e.

con-

be negative.

One

3.

IV

or the other of the premisses

must be

universal.

2nd of the Major Term. Figs. I and 3. If the conclusion is negative, the major must be negative; i.e. (in either case) the minor mtist be affirmative.

Figs. 2 and 4. If the conclusion major must be universal.

is

negative, the

^rd of the Minor Term.

and 2. If the minor is particular, the conclusion must be particular. Figs. 3 and 4. If the minor is affirmative, the conclusion must be particular. Figs.

I

These rules have been grouped by reference to the term (middle, major or minor) which has to be correctly distributed. They will now be grouped by reference to the figure (ist, 2nd, 3rd or 4th) to which each applies. In this rearrangement we shall also simplify the formulations by replacing where possible a hypothetically formulated rule by one categorically formulated. As a basis of this reformulation

we

take the rules of quality

3, which have already been expressed categorically; viz. for Figs, i and 3: 'The minor premiss must be affirmative,' and for Fig. 2: 'The conclusion must be negative.' Conjoining the categorical

for Figs.

I,

2

and

rule (of quality) for Fig.

i

with

its

hypothetical rule,

minor is affirmative the major must be universal,' we deduce for this figure the categorical rule (of quantity), '

If the

'The major must be universal' Again, conjoining the

THE CATEGORICAL SYLLOGISM

•Lie (U

-^

1-

>-

«'5 ^ h

^

> 3

^

ei

.i^

S?-^-5=.°15§ (14

i.i°sli

^ o

c

l-cs

-s

rt

5

!£

.2

S~

rt

'35

ir

O c

Co

.28=2

< w

.H,

2

5 < w

^ •^

«o

w w

{A, B, C) for all values of A, B, C, where all the variables are variables

FUNCTIONAL DEDUCTION

127

and the equation therefore contains no such symbol as that can be exhibited as dependent upon the others. The distinction between these two typesof equation is familiarto mathematicians the former may be called a limiting, the latter a nonindependently variable,

P

The

limiting equation.

limiting equation

is

generally

used to determine one or other of the quantities P, A, B, or C, in terms of the remainder; so that here we associate the antithesis between dependent and independent with the antithesis between unknown and

known; whereas, in the non-limiting equation, no one of the variables can be regarded as unknown and as such expressible in terms of the others regarded as known. The distinctions that have been put forward between these two types of functional process are tanta-

mount

to defining the functional syllogism as that

which proves factual conclusions from factual premisses, and functional deduction as that which proves formal conclusions or formulae from formal premisses, i.e. from formulae previously established.

It will further be observed, from the simple illustrations which follow, that whereas the functional syllogism requires only the one

functional equation that serves as major premiss, the

process of functional deduction will necessarily involve

a conjunction of two or more functional equations, all of which are, as above explained, formal and not factual.

To

illustrate the

deduction,

/{a,

which

is

general formula used in functional

viz. b,

c,

...)

= (j){a,

b, c,

...)

understood to hold for every value of the

CHAPTER

128

A, B,

variables

C, ...,

VI

we may

instance the following

elementary examples: {a

and

+ d)x{a-d) = a'-d' axd = dxa,

both of which involve two variables; and again

=a + {d + c)

{a-{-d)-\-c

and

{a

+ d)xc

={axc)-\-(dxc),

The

both of which involve three variables. formulae are

known

last

three

respectively as the Commutative,

the Associative and the Distributive Law. § 4.

In the functional equations of mathematics

it

is

important to realise the range of universality covered by

any functional formula. This range depends upon the numberof independent variables involved in the formula, the range being wider or narrower according as the

num.ber of independent variables

For example, supposing 7, 5,

larger or smaller.

is

have respectively

that x, y, z

10 possible values; then the numberof applications

x

of the formula involving

involving

involving

number

x and y alone x and y and 2

alone

is 7,

that of a formula

and that of a formula

is

35,

is

350.

And

in general, the

of applications of a formula

is

equal to the

numbers of possible values for the variables involved. Now the number of possible values of any variable occurring in logical or mathe-

arithmetical product of the

matical formulae spectively of

I,

is 2,

infinite;

3...

hence, for the cases re-

variables, the

corresponding

00 \.., constiranges of application would be 00, 00 tuting a series of continually higher orders of infinity "^j

or rather, in accordance with Cantor's arithmetic, each of the ranges of application for

i,

2,

3

...

variables

is

a

FUNCTIONAL DEDUCTION proper part of that for cardinal

129

successor, although their

its

numbers are the same.

Now it will be found that,

in inferences of the

of functional deduction, the derived formula a range of application to or

Thus

— not narrower

the

answer

word deduction

may have

than but

even wider than that from which

it

nature

is

— equal

derived.

as here applied does not

to the usual definition of deduction (illustrated

especially in the syllogism) as inference from the generic to the specific;

although the only fundamental principle

employed in the process is the Applicative, according which we replace either a variable symbol by one of its determinates or one determinate variant by another. But here a distinction must be made according as the substituted symbol is simple or compound. If we merely replace any one of the simple symbols a, b, c by some other simple symbol we shall not obtain a really new to

formula, since the formula

is

for all substitutable values,

indifference whether

the symbols

a, b,

to be interpreted as holding and hence it is a matter of

we express

the formula in terms of

(say) or oi p, q,r.

c,

In order to deduce

new formulae, it is necessary to replace two or more simple symbols by connected compounds.

For those unfamiliar with mathematical methods, it when any compound symbol is substituted for a simple, the compound must be enclosed in a bracket or be shown by some device to

should be pointed out that,

constitute a single symbolic unit.

always replace

in

Though we may

a general formula a simple by a com-

pound symbol, the reverse does not by any means hold without exception. tion

is

The

cases in which such substitu-

permissible have been partially explained in the

J. L. II

9

CHAPTER

130

VI

chapter on Symbolism and Functions.

shown

that,

if

formula

a

involves

There

was

it

such compound

symbols or sub-constructs as f{a, b\ f{c, d) etc., and only such, where none of the simple symbols used in the one bracketed sub-construct occur in any of the others, then these bracketed functions are called dis-

connected.

It is in

the case of disconnected functions

that free substitutions of simple symbols for the

pound are

The

permissible.

reason for this

is

com-

that, for

the notion of a function of any given variants,

it

is

essential that these shall be variable independently of

one another.

Now, when

the different sub-constructs

or bracketed functions are connected with one another

through identity of some simple symbol, say clear that

these

we cannot contemplate

compounds without

its

a,

it

is

a variation of one of

involving a variation of the

other connected compounds.

Hence we should be

vio-

lating the fundamental principle of independent variability

of the variants,

if

we

freely substituted for such

connected compounds simple symbols which would have to

be understood as capable of independent variation.

Hence,

it is

only

when the various compounds involved

in a function are

unconnected, that for each of such

compounds a simple symbol may be § 5.

substituted.

Returning to the problem under immediate con-

sideration, a simple illustration from algebra will

show

how, by making appropriate substitutions in a given functional formula, we may demonstrate a new formula. Thus, having established the formula that for all values of X and

y (i)

we may substitute

{x+y)x{x-y)=x'-f for xa.ndy, respectively, the connected

FUNCTIONAL DEDUCTION compounds

a-\-b

and a

— b\ and

so deduce (by means of

the distributive law for multiplication

values of a and

131

etc.) that for all

b^

(ii)

\ab^{a-^by-(a-b)\

This is a new formula, different from the previous one, because the relation between a and b predicated in (ii) is different from the relation between x and y predicated in (i). Moreover the range of application for (ii) is no narrower than that for (i); for (i) applies for every diad or couple 'x tojK,' and (ii) for every diad or couple 'a to

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