H. A. (Harold Arthur) Prichard.

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KANT'S THEORY OF KNOWLEDGE

by

H. A. PRICHARD

Fellow of Trinity College, Oxford







Oxford
At the Clarendon Press
1909

Henry Frowde, M.A.
Publisher to the University of Oxford
London, Edinburgh, New York
Toronto and Melbourne




PREFACE


This book is an attempt to think out the nature and tenability of
Kant's Transcendental Idealism, an attempt animated by the conviction
that even the elucidation of Kant's meaning, apart from any criticism,
is impossible without a discussion on their own merits of the main
issues which he raises.

My obligations are many and great: to Caird's _Critical Philosophy of
Kant_ and to the translations of Meiklejohn, Max Müller, and Professor
Mahaffy; to Mr. J. A. Smith, Fellow of Balliol College, and to Mr. H.
W. B. Joseph, Fellow of New College, for what I have learned from them
in discussion; to Mr. A. J. Jenkinson, Fellow of Brasenose College,
for reading and commenting on the first half of the MS.; to Mr. H. H.
Joachim, Fellow of Merton College, for making many important
suggestions, especially with regard to matters of translation; to Mr.
Joseph, for reading the whole of the proofs and for making many
valuable corrections; and, above all, to my wife for constant and
unfailing help throughout, and to Professor Cook Wilson, to have been
whose pupil I count the greatest of philosophical good fortunes. Some
years ago it was my privilege to be a member of a class with which
Professor Cook Wilson read a portion of Kant's _Critique of Pure
Reason_, and subsequently I have had the advantage of discussing with
him several of the more important passages. I am especially indebted
to him in my discussion of the following topics: the distinction
between the Sensibility and the Understanding (pp. 27-31, 146-9,
162-6), the term 'form of perception' (pp. 37, 40, 133 fin.-135), the
_Metaphysical Exposition of Space_ (pp. 41-8), Inner Sense (Ch. V,
and pp. 138-9), the _Metaphysical Deduction of the Categories_ (pp.
149-53), Kant's account of 'the reference of representations to an
object' (pp. 178-86), an implication of perspective (p. 90), the
impossibility of a 'theory' of knowledge (p. 245), and the points
considered, pp. 200 med.-202 med., 214 med.-215 med., and 218. The
views expressed in the pages referred to originated from Professor
Cook Wilson, though it must not be assumed that he would accept them
in the form in which they are there stated.




CONTENTS


CHAPTER I PAGE
THE PROBLEM OF THE _Critique_ 1

CHAPTER II
THE SENSIBILITY AND THE UNDERSTANDING 27

CHAPTER III
SPACE 36

CHAPTER IV
PHENOMENA AND THINGS IN THEMSELVES 71

NOTE
THE FIRST ANTINOMY 101

CHAPTER V
TIME AND INNER SENSE 103

CHAPTER VI
KNOWLEDGE AND REALITY 115

CHAPTER VII
THE METAPHYSICAL DEDUCTION OF THE CATEGORIES 140

CHAPTER VIII
THE TRANSCENDENTAL DEDUCTION OF THE CATEGORIES 161

CHAPTER IX
GENERAL CRITICISM OF THE TRANSCENDENTAL DEDUCTION OF THE
CATEGORIES 214

CHAPTER X
THE SCHEMATISM OF THE CATEGORIES 246

CHAPTER XI
THE MATHEMATICAL PRINCIPLES 260

CHAPTER XII
THE ANALOGIES OF EXPERIENCE 268

CHAPTER XIII
THE POSTULATES OF EMPIRICAL THOUGHT 308

NOTE
THE REFUTATION OF IDEALISM 319




REFERENCES


A = First edition of the _Critique of Pure Reason_.
B = Second edition of the _Critique of Pure Reason_.
Prol. = Kant's _Prolegomena to any future Metaphysic_.
M = Meiklejohn's Translation of the _Critique of Pure Reason_.
Mah. = Mahaffy. Translation of Kant's _Prolegomena to any future
Metaphysic_. (The pages referred to are those of the first
edition; these are also to be found in the text of the
second edition.)
Caird = Caird's _Critical Philosophy of Kant_.




CHAPTER I

THE PROBLEM OF THE _CRITIQUE_


The problem of the _Critique_ may be stated in outline and
approximately in Kant's own words as follows.

Human reason is called upon to consider certain questions, which it
cannot decline, as they are presented by its own nature, but which it
cannot answer. These questions relate to God, freedom of the will, and
immortality. And the name for the subject which has to deal with these
questions is metaphysics. At one time metaphysics was regarded as the
queen of all the sciences, and the importance of its aim justified the
title. At first the subject, propounding as it did a dogmatic system,
exercised a despotic sway. But its subsequent failure brought it into
disrepute. It has constantly been compelled to retrace its steps;
there has been fundamental disagreement among philosophers, and no
philosopher has successfully refuted his critics. Consequently the
current attitude to the subject is one of weariness and indifference.
Yet humanity cannot really be indifferent to such problems; even those
who profess indifference inevitably make metaphysical assertions; and
the current attitude is a sign not of levity but of a refusal to put
up with the illusory knowledge offered by contemporary philosophy. Now
the objects of metaphysics, God, freedom, and immortality, are not
objects of experience in the sense in which a tree or a stone is an
object of experience. Hence our views about them cannot be due to
experience; they must somehow be apprehended by pure reason, i. e. by
thinking and without appeal to experience. Moreover, it is in fact by
thinking that men have always tried to solve the problems concerning
God, freedom, and immortality. What, then, is the cause of the
unsatisfactory treatment of these problems and men's consequent
indifference? It must, in some way, lie in a failure to attain the
sure scientific method, and really consists in the neglect of an
inquiry which should be a preliminary to all others in metaphysics.
Men ought to have begun with a critical investigation of pure reason
itself. Reason should have examined its own nature, to ascertain in
general the extent to which it is capable of attaining knowledge
without the aid of experience. This examination will decide whether
reason is able to deal with the problems of God, freedom, and
immortality at all; and without it no discussion of these problems
will have a solid foundation. It is this preliminary investigation
which the _Critique of Pure Reason_ proposes to undertake. Its aim is
to answer the question, 'How far can reason go, without the material
presented and the aid furnished by experience?' and the result
furnishes the solution, or at least the key to the solution, of all
metaphysical problems.

Kant's problem, then, is similar to Locke's. Locke states[1] that his
purpose is to inquire into the original, certainty, and extent of
human knowledge; and he says, "If, by this inquiry into the nature of
the understanding I can discover the powers thereof; how far they
reach, to what things they are in any degree proportionate, and where
they fail us; I suppose it may be of use to prevail with the busy mind
of man, to be more cautious in meddling with things exceeding its
comprehension; to stop when it is at the utmost extent of its tether;
and to sit down in a quiet ignorance of those things, which, upon
examination, are found to be beyond the reach of our capacities."
Thus, to use Dr. Caird's analogy,[2] the task which both Locke and
Kant set themselves resembled that of investigating a telescope,
before turning it upon the stars, to determine its competence for the
work.

[1] Locke's _Essay_, i, 1, §§ 2, 4.

[2] Caird, i, 10.

The above outline of Kant's problem is of course only an outline. Its
definite formulation is expressed in the well-known question, 'How are
_a priori_ synthetic judgements possible?'[3] To determine the meaning
of this question it is necessary to begin with some consideration of
the terms '_a priori_' and 'synthetic'.

[3] B. 19, M. 12.

While there is no difficulty in determining what Kant would have
recognized as an _a priori_ judgement, there is difficulty in
determining what he meant by calling such a judgement _a priori_. The
general account is given in the first two sections of the
Introduction. An _a priori_ judgement is introduced as something
opposed to an _a posteriori_ judgement, or a judgement which has its
source in experience. Instances of the latter would be 'This body is
heavy', and 'This body is hot'. The point of the word 'experience' is
that there is direct apprehension of some individual, e. g. an
individual body. To say that a judgement has its source in experience
is of course to imply a distinction between the judgement and
experience, and the word 'source' may be taken to mean that the
judgement depends for its validity upon the experience of the
individual thing to which the judgement relates. An _a priori_
judgement, then, as first described, is simply a judgement which is
not _a posteriori_. It is independent of all experience; in other
words, its validity does not depend on the experience of individual
things. It might be illustrated by the judgement that all three-sided
figures must have three angles. So far, then, no positive meaning has
been given to _a priori_.[4]

[4] Kant is careful to exclude from the class of _a priori_
judgements proper what may be called relatively _a priori_
judgements, viz. judgements which, though not independent of
all experience, are independent of experience of the facts to
which they relate. "Thus one would say of a man who
undermined the foundations of his house that he might have
known _a priori_ that it would fall down, i. e. that he did
not need to wait for the experience of its actual falling
down. But still he could not know this wholly _a priori_, for
he had first to learn through experience that bodies are
heavy and consequently fall, if their supports are taken
away." (B. 2, M. 2.)

Kant then proceeds, not as we should expect, to state the positive
meaning of _a priori_; but to give tests for what is _a priori_. Since
a test implies a distinction between itself and what is tested, it is
implied that the meaning of _a priori_ is already known.[5]

[5] It may be noted that in this passage (Introduction, §§ 1
and 2) Kant is inconsistent in his use of the term 'pure'.
Pure knowledge is introduced as a species of _a priori_
knowledge: "_A priori_ knowledge, if nothing empirical is
mixed with it, is called pure". (B. 3, M. 2, 17.) And in
accordance with this, the proposition 'every change has a
cause' is said to be _a priori_ but impure, because the
conception of change can only be derived from experience. Yet
immediately afterwards, pure, being opposed in general to
empirical, can only mean _a priori_. Again, in the phrase
'pure _a priori_' (B. 4 fin., M. 3 med.), the context shows
that 'pure' adds nothing to '_a priori_', and the proposition
'every change must have a cause' is expressly given as an
instance of pure _a priori_ knowledge. The inconsistency of
this treatment of the causal rule is explained by the fact
that in the former passage he is thinking of the conception
of change as empirical, while in the latter he is thinking of
the judgement as not empirical. At bottom in this passage
'pure' simply means _a priori_.

The tests given are necessity and strict universality.[6] Since
judgements which are necessary and strictly universal cannot be based
on experience, their existence is said to indicate another source of
knowledge. And Kant gives as illustrations, (1) any proposition in
mathematics, and (2) the proposition 'Every change must have a cause'.

[6] In reality, these tests come to the same thing, for
necessity means the necessity of connexion between the
subject and predicate of a judgement, and since empirical
universality, to which strict universality is opposed, means
numerical universality, as illustrated by the proposition
'All bodies are heavy', the only meaning left for strict
universality is that of a universality reached not through an
enumeration of instances, but through the apprehension of a
necessity of connexion.

So far Kant has said nothing which determines the positive meaning of
_a priori_. A clue is, however, to be found in two subsequent phrases.
He says that we may content ourselves with having established as a
fact the pure use of our faculty of knowledge.[7] And he adds that not
only in judgements, but even in conceptions, is an _a priori_ origin
manifest.[8] The second statement seems to make the _a priori_
character of a judgement consist in its origin. As this origin cannot
be experience, it must, as the first statement implies, lie in our
faculty of knowledge. Kant's point is that the existence of universal
and necessary judgements shows that we must possess a faculty of
knowledge capable of yielding knowledge without appeal to experience.
The term _a priori_, then, has some reference to the existence of this
faculty; in other words, it gives expression to a doctrine of 'innate
ideas'. Perhaps, however, it is hardly fair to press the phrase
'_test_ of _a priori_ judgements'. If so, it may be said that on the
whole, by _a priori_ judgements Kant really means judgements which are
universal and necessary, and that he regards them as implying a
faculty which gives us knowledge without appeal to experience.

[7] B. 5, M. 4.

[8] Ibid.

We may now turn to the term 'synthetic judgement'. Kant distinguishes
analytic and synthetic judgements thus. In any judgement the predicate
B either belongs to the subject A, as something contained (though
covertly) in the conception A, or lies completely outside the
conception A, although it stands in relation to it. In the former case
the judgement is called analytic, in the latter synthetic.[9] 'All
bodies are extended' is an analytic judgement; 'All bodies are heavy'
is synthetic. It immediately follows that only synthetic judgements
extend our knowledge; for in making an analytic judgement we are only
clearing up our conception of the subject. This process yields no new
knowledge, for it only gives us a clearer view of what we know
already. Further, all judgements based on experience are synthetic,
for it would be absurd to base an analytical judgement on experience,
when to make the judgement we need not go beyond our own conceptions.
On the other hand, _a priori_ judgements are sometimes analytic and
sometimes synthetic. For, besides analytical judgements, all
judgements in mathematics and certain judgements which underlie
physics are asserted independently of experience, and they are
synthetic.

[9] B. 10, M. 7.

Here Kant is obviously right in vindicating the synthetic character of
mathematical judgements. In the arithmetical judgement 7 + 5 = 12, the
thought of certain units as a group of twelve is no mere repetition of
the thought of them as a group of five added to a group of seven.
Though the same units are referred to, they are regarded differently.
Thus the thought of them as twelve means either that we think of them
as formed by adding one unit to a group of eleven, or that we think of
them as formed by adding two units to a group of ten, and so on. And
the assertion is that the same units, which can be grouped in one way,
can also be grouped in another. Similarly, Kant is right in pointing
out that the geometrical judgement, 'A straight line between two
points is the shortest,' is synthetic, on the ground that the
conception of straightness is purely qualitative,[10] while the
conception of shortest distance implies the thought of quantity.

[10] Straightness means identity of direction.

It should now be an easy matter to understand the problem expressed
by the question, 'How are _a priori_ synthetic judgements possible?'
Its substance may be stated thus. The existence of _a posteriori_
synthetic judgements presents no difficulty. For experience is
equivalent to perception, and, as we suppose, in perception we are
confronted with reality, and apprehend it as it is. If I am asked,
'How do I know that my pen is black or my chair hard?' I answer that
it is because I see or feel it to be so. In such cases, then, when my
assertion is challenged, I appeal to my experience or perception of
the reality to which the assertion relates. My appeal raises no
difficulty because it conforms to the universal belief that if
judgements are to rank as knowledge, they must be made to conform to
the nature of things, and that the conformity is established by appeal
to actual experience of the things. But do _a priori_ synthetic
judgements satisfy this condition? Apparently not. For when I assert
that every straight line is the shortest way between its extremities,
I have not had, and never can have, experience of all possible
straight lines. How then can I be sure that all cases will conform to
my judgement? In fact, how can I anticipate my experience at all? How
can I make an assertion about any individual until I have had actual
experience of it? In an _a priori_ synthetic judgement the mind in
some way, in virtue of its own powers and independently of experience,
makes an assertion to which it claims that reality must conform. Yet
why should reality conform? _A priori_ judgements of the other
kind, viz. analytic judgements, offer no difficulty, since they
are at bottom tautologies, and consequently denial of them is
self-contradictory and meaningless. But there is difficulty where a
judgement asserts that a term B is connected with another term A, B
being neither identical with nor a part of A. In this case there is no
contradiction in asserting that A is not B, and it would seem that
only experience can determine whether all A is or is not B. Otherwise
we are presupposing that things must conform to our ideas about them.
Now metaphysics claims to make _a priori_ synthetic judgements, for it
does not base its results on any appeal to experience. Hence, before
we enter upon metaphysics, we really ought to investigate our right to
make _a priori_ synthetic judgements at all. Therein, in fact, lies
the importance to metaphysics of the existence of such judgements in
mathematics and physics. For it shows that the difficulty is not
peculiar to metaphysics, but is a general one shared by other
subjects; and the existence of such judgements in mathematics is
specially important because there their validity or certainty has
never been questioned.[11] The success of mathematics shows that at any
rate under certain conditions _a priori_ synthetic judgements are
valid, and if we can determine these conditions, we shall be able to
decide whether such judgements are possible in metaphysics. In this
way we shall be able to settle a disputed case of their validity by
examination of an undisputed case. The general problem, however, is
simply to show what it is which makes _a priori_ synthetic judgements
as such possible; and there will be three cases, those of mathematics,
of physics, and of metaphysics.

[11] Kant points out that this certainty has usually been
attributed to the analytic character of mathematical
judgements, and it is of course vital to his argument that
he should be successful in showing that they are really
synthetic.

The outline of the solution of this problem is contained in the
Preface to the Second Edition. There Kant urges that the key is to be
found by consideration of mathematics and physics. If the question be
raised as to what it is that has enabled these subjects to advance, in
both cases the answer will be found to lie in a change of method.
"Since the earliest times to which the history of human reason
reaches, mathematics has, among that wonderful nation the Greeks,
followed the safe road of a science. Still it is not to be supposed
that it was as easy for this science to strike into, or rather to
construct for itself, that royal road, as it was for logic, in which
reason has only to do with itself. On the contrary, I believe that it
must have remained long in the stage of groping (chiefly among the
Egyptians), and that this change is to be ascribed to a _revolution_,
due to the happy thought of one man, through whose experiment the path
to be followed was rendered unmistakable for future generations, and
the certain way of a science was entered upon and sketched out once
for all.... A new light shone upon the first man (Thales, or whatever
may have been his name) who demonstrated the properties of the
isosceles triangle; for he found that he ought not to investigate
that which he saw in the figure or even the mere conception of the
same, and learn its properties from this, but that he ought to produce
the figure by virtue of that which he himself had thought into it _a
priori_ in accordance with conceptions and had represented (by means
of a construction), and that in order to know something with certainty
_a priori_ he must not attribute to the figure any property other than
that which necessarily follows from that which he has himself
introduced into the figure, in accordance with his conception."[12]

[12] B. x-xii, M. xxvi.

Here Kant's point is as follows. Geometry remained barren so long as
men confined themselves either to the empirical study of individual
figures, of which the properties were to be discovered by observation,
or to the consideration of the mere conception of various kinds of
figure, e. g. of an isosceles triangle. In order to advance, men had
in some sense to produce the figure through their own activity, and in
the act of constructing it to recognize that certain features were
necessitated by those features which they had given to the figure in
constructing it. Thus men had to make a triangle by drawing three
straight lines so as to enclose a space, and then to recognize that
three angles must have been made by the same process. In this way the
mind discovered a general rule, which must apply to all cases, because
the mind itself had determined the nature of the cases. A property B
follows from a nature A; all instances of A must possess the property
B, because they have solely that nature A which the mind has given
them and whatever is involved in A. The mind's own rule holds good in
all cases, because the mind has itself determined the nature of the
cases.

Kant's statements about physics, though not the same, are analogous.
Experiment, he holds, is only fruitful when reason does not follow
nature in a passive spirit, but compels nature to answer its own
questions. Thus, when Torricelli made an experiment to ascertain
whether a certain column of air would sustain a given weight, he had
previously calculated that the quantity of air was just sufficient to
balance the weight, and the significance of the experiment lay in his