Norman Kemp Smith.

A commentary to Kant's 'Critique of pure reason,' online

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two lines of enquiry.

The wider issue is the generating problem of Kant's
Critique : How in a judgment can a predicate be asserted of
a subject in which it is not already involved ? In other words,
what is it that in such a case justifies us in connecting the
predicate with the subject ? Though this problem was never
directly raised by any pre-Kantian thinker, not even by
Hume, it is absolutely vital to all the pre-Kantian systems.
Thus Descartes' philosophy is based upon a distinction,
nowhere explicitly drawn but everywhere silently assumed,
between abstract and fruitful ideas. The former contain just
so much content and no more ; this content may be explicitly
unfolded in a series of judgments, but no addition is thereby
made to our knowledge. The latter, on the other hand, are
endowed with an extraordinary power of inner growth. To
the attentive mind they disclose a marvellous variety of inner
meaning. The chief problem of scientific method consists,
according to Descartes, in the discovery of these fruitful
ideas, and in the separation of them from the irrelevant
accompaniments which prevent them from unfolding their
inner content. Once they are discovered, the steady progress
of knowledge is assured. They are the springs of knowledge,
and from them we have only to follow down the widening
river of truth.

Descartes professed to give a complete list of the possible
fruitful ideas. They are, he claimed, better known than any
other concepts. They lie at the basis of all experience, and
no one can possibly be ignorant of them ; though, owing to
their simplicity and omnipresence, their philosophical import-
ance has been overlooked. When, however, Descartes pro-
ceeded to classify them, he found that while such ideas as
space, triangle, number, motion, contain an inexhaustible


content that is progressively unfolded in the mathematical
sciences, those ideas, on the other hand, through which we
conceive mental existences, the notions of mind, thought,
se lf_do not by any means prove fruitful upon attentive
enquiry. As Malebranche later insisted, we can define mind
only in negative terms ; its whole meaning is determined
through its opposition to the space -world, which alone is
truly known. Though it is the function of mind to know, it
cannot know itself. And when we remove from our list of
ideas those which are not really fruitful, we find that only
mathematical concepts remain. 1 They alone have this ap-
parently miraculous property of inexhaustibly developing
before the mind. Scientific knowledge is limited to the
material world ; and even there, the limits of our mathematical
insight are the limits of our knowledge.

Malebranche believed no less thoroughly than Descartes
in the asserted power and fruitfulness of mathematical con-
cepts. Under the influence of this belief, he developed, as so
many other thinkers from Plato onwards have done, a highly
mystical theory of scientific knowledge. It is a revelation of
eternal truth, and yet is acquired by inner reflection, not
laboriously built up by external observation. It comes by
searching of the mind, not by exploration of the outer world.
But Malebranche was not content, like Descartes, merely to
accept this type of knowledge. He proceeded to account for
it in metaphysical terms. The fruitfulness of mathematical
ideas is due, he claimed, to the fundamental concept of ex-
tension in which they all share. This idea, representing, as it
does, an infinite existence, is too great to be contained within
the finite mind. Through it the mind is widened to the
apprehension of something beyond itself; we know it through
consciousness of its archetype in the mind of God. It is the
one point at which consciousness transcends its subjective
limits. Its fruitfulness is due to, and is the manifestation of,
this divine source. The reason why we are condemned to
remain ignorant of everything beyond the sphere of quantity
is that extension alone holds this unique position. It is the
only fruitful idea which the mind possesses, and other concepts,
such as triangle, circle, or number, are fruitful only in pro-
portion as they share in it. We can acquire no genuine
knowledge even of the nature of the self. Being ignorant
of mind, we cannot comprehend the self which is one of its
modes. It is as if we sought to comprehend the nature of
a triangle, in the absence of any conception of space. Were

1 On Descartes' failure to distinguish between the mathematical and the
dynamical aspects of motion, cf. above, p. 584.


we in possession of the archetypal idea of mind, we should
not only be able to deduce from it those various feelings and
emotions which we have already -experienced, and those
sensations of the secondary qualities which we falsely ascribe
to the influence of external objects, but we should also be
able to discover by pure contemplation innumerable other
emotions and qualities, which entirely transcend our present
powers. And all of these would then be experienced in their
ideal nature, and not, as now, merely through feeble and
confused feeling. If mathematicians destroy their bodily
health through absorption in the progressive clarification of
the mysteries of space, what might not happen if the arche-
typal idea of mind were revealed to us ? Could we attend to
the preservation of a body which would incessantly distract
us from the infinite and overwhelming experiences of our
divine destiny ?

This romantic conception of the possibilities of rational
science reveals more clearly than any other Cartesian doctrine
the real bearing and perverse character of the rationalistic
preconceptions which underlie the Cartesian systems. The
Cartesians would fain make rational science, conceived on
the analogy of the mathematical disciplines, coextensive with
the entire realm of the real. This grotesque enterprise is
conceived as abstractly possible even by so cautious a thinker
as John Locke. His reason for condemning the physical
sciences as logically imperfect is that they fail to conform to
this rationalistic ideal. Hence those sentences which sound
so strangely in the mouth of Locke, the sensationalist.

" It is the contemplation of our abstract ideas that alone is able
to afford us general knowledge." l " The true method of advancing
knowledge is by considering our abstract ideas." 2 "[Did we know
the real essence of gold] it would be no more necessary that
gold should exist, and that we should make experiments upon it,
than it is necessary for the knowing of the properties of a triangle,
that a triangle should exist in any matter: the idea in our minds
would serve for the one as well as for the other." 3 " In the know-
ledge of bodies, we must be content to glean what we can from
particular experiments, since we cannot, from a discovery of their
real essences, grasp at a time whole sheaves, and in bundles com-
prehend the nature and the properties of whole species together." 4

Locke's empirical doctrine of knowledge is thus based
upon a rationalistic theory of the real. It is not, he holds,
the constitution of reality, but the de facto limitations of our

1 Essay concerning Human Understanding, IV. vi. 16.

2 Op. cit. IV. xii. 7. 3 Op. cit. IV. vi. 11.


human faculties which make empirical induction the only
practicable mode of discovery in natural science. Indeed,
Locke gives more extreme expression than even Descartes
does, to the mystically conceived mathematical method.
Being ignorant of mathematics, and not over well-informed
even in the physical sciences, Locke was not checked by any
too close acquaintance with the real character and necessary
limits of this method ; and he accordingly makes statements
in that unqualified fashion which seldom fails to betray the
writer who is expounding views which he has not developed"
for himself by first-hand study of the relevant facts.

But though the unique character of mathematical know-
ledge thus forced itself upon the attention of all the Cartesian
thinkers, and in the above manner led even the most level-
headed of Descartes' successors to dream strange dreams,
no real attempt was made (save in the neglected writings of
Leibniz) to examine, in a sober spirit, the grounds and con-
ditions of its possibility. In the English School, Locke's
eulogy of abstract ideas served only to drive his immediate
successors to an opposite extreme. Both Berkeley and Hume
attempted to explain away, in an impossible manner, those
fundamental differences, which, beyond all questioning, pro-
foundly differentiate mathematical from empirical judgments. 1
It is not surprising that Kant, who had no direct acquaintance
with Hume's Treatise, should have asserted that had Hume
realised the bearing of his main teaching upon the theory of
mathematical science, he would have hesitated to draw his
sceptical conclusions. Such, however, was not the case.
Hume's theory of mathematical, reasoning undoubtedly forms
the least satisfactory part of his philosophy. He did, however,
perceive the general bearing of his central teaching. It was
in large degree his ignorance of the mathematical disciplines
that concealed from him the thorough unsatisfactoriness of his
general position, and which prevented him from formulating
the logical problem in its full scope the problem, namely,
how judgments which make additions to our previous know-
ledge, and yet do not rest upon mere sensation, are possible.
He treated it only as it presents itself in those judgments
which involve the concept of causality. 2 But this analysis of
causal judgments awoke Kant from his dogmatic slumber, and
so ultimately led to the raising of the logical problem in its
widest form : how synthetic a priori judgments, whether
mathematical, physical, or metaphysical, are possible.

1 Cf. above, pp. 27-8.

2 Though the concept of substance is also discussed by Hume, his treatment
of it is quite perfunctory.


Hume discussed the causal problem both in regard to the
general principle of causality and in its bearing upon our
particular judgments of causal relation. The problems con-
cerned in these two discussions are essentially distinct. The
first involves immensely wider issues, and so far as can be
judged from the existing circumstantial evidence, 1 it was this
first discussion, not as has been so often assumed by Kant's
commentators the second and more limited problem, which
exercised so profound an influence upon Kant at the turning-
point of his speculations. In stating it, it will be best to take
Hume's own words.

" To begin with the first question concerning the necessity of a
cause : 'Tis a general maxim in philosophy, that whatever begins to
exist, must have a cause of existence. This is commonly taken for
granted in all reasonings, without any proof given or demanded.
'Tis supposed to be founded on intuition, and to be one of those
maxims, which though they may be deny'd with the lips, 'tis impos-
sible for men in their hearts really to doubt of. But if we examine
this maxim by the idea of knowledge above explain'd we shall discover
in it no mark of any such intuitive certainty; but on the contrary
shall find, that 'tis of a nature quite foreign to that species of con-
viction." 2

The principle that every event must have a cause, is
neither intuitively nor demonstratively certain. So far from
there existing a necessary connection between the idea of an
event as something happening in time and the idea of a cause,
no connection of any kind is discoverable by us. We can
conceive an object to be non-existent at this moment, and
existent the next, without requiring to conjoin with it the
altogether different idea of a productive source.

This had been implicitly recognised by those few philo-
sophers who had attempted to give demonstrations of the
principle. By so doing, however, they only reinforce Hume's
contention that it possesses no rational basis. When Hobbes
argues that as all the points of time and place in which we can
suppose an object to begin to exist, are in themselves equal,
there must be some cause determining an event to happen at
one moment rather than at another, he is assuming the very
principle which he professes to prove. There is no greater
difficulty in supposing the time and place to be fixed without
a cause, than in supposing the existence to be so determined.
If the denial of a cause is not intuitively absurd in the one
case, it cannot be so in the other. If the first demands a

1 Cf. above, pp. xxv ff., 6 1 ff.
2 Treatise on Human Nature (Green and Grose), i. p. 380.



proof, so likewise must the second. Similarly with the argu-
ments advanced by Locke and Clarke. Locke argues that if
anything is produced without a cause, it is produced by
nothing, and that that is impossible, since nothing can never
be a cause any more than it can be something, or equal to
two right angles. Clarke's contention that if anything were
without a cause, it would produce its elf , i.e. exist before it
existed, is of the same character. These arguments assume
the only point which is in question.

"When we exclude all causes we really do exclude them, and
neither suppose nothing nor the object itself to be the causes of the
existence, and consequently can draw no argument from the absurdity
of these suppositions to prove the absurdity of that exclusion." 1

The remaining argument, that every effect must have a
cause, since this is implied in the very idea of an effect, is
" still more frivolous."

" Every effect necessarily presupposes a cause ; effect being a
relative term, of which cause is the correlative. But this does not
prove that every being must be preceded by a cause ; no more than
it follows, because every husband must have a wife, that therefore
every man must be married." 2

The far-reaching conclusion, that the principle of causality
has no possible rational basis, Hume extends and reinforces
through his other doctrines, viz. that synthetic reason 3 is
merely generalised belief, and that belief is in all cases due to
the ultimate instincts and propensities which de facto constitute
our human nature. The synthetic principles which lie at the
basis of our experience are non-rational in character. Each is
due to a * blind and powerful instinct,' which, demanding no
evidence, and ignoring theoretical inconsistency for the sake
of practical convenience, necessitates belief.

" Nature by an absolute and uncontrollable necessity has deter-
mined us to judge as well as to breathe and feel." 4 "All these
operations are a species of natural instincts, which no reasoning or
process of the thought and understanding is able either to produce or
to prevent." 5

Reason is "nothing but a wonderful and unintelligible
instinct in our souls." 6 It justifies itself by its practical uses,

1 Op. cit. p. 383. a LoCf ciL

For justification of the phrase " synthetic reason," I must refer to my articles
m Mind, vol. xiv. N.S..pp. 14973, 335-47. on "The Naturalism of Hume."
Treatise (Green and Grose), i. pp. 474-5.

5 Enquiry concerning Human Understanding (Green and Grose), p. 40.

6 Treatise ', p. 471.


but can afford no standard to which objective reality must

It is from this point of view that Hume states his answer
to the problem of perception. Our natural belief in the per-
manence and identity of objects, as expressed through the
principle of substance and attribute, leads us to interpret the
objects of sense-perception as independent realities. We inter-
pret our subjective sensations as being qualities of independent
substances. Our other natural belief, in the dynamical inter-
dependence of events, as expressed through the principle of
causality, leads, however, to the opposite conclusion, that the
known objects are merely mental. For by it we are con-
strained to interpret sensations, not as objective qualities, but
only as subjective effects, expressive of the reactions of our
psycho -physical organism. The Cartesian problems owe
their origin to the mistaken attempt to harmonise, in a
theoretical fashion, these two conflicting principles. The
conflict is inevitable and the antinomy is insoluble, so long
as the two principles are regarded as objectively valid. The
only satisfactory solution comes through recognition that
reason is unable to account, save in reference to practical
ends, even for its own inevitable demands. The principle
of substance and attribute and the principle of causality
co-operate in rendering possible such organisation of our
sense-experience as is required for practical life. But when
we carry this organisation further than practical life itself
demands, the two principles at once conflict.

Kant shows no interest in this constructive part of
Hume's philosophy ; and must, indeed, have been almost
entirely ignorant of it, since it finds only -very imperfect ex-
pression in the Enquiry, and is ignored in Beattie's Nature
of Truth. Accordingly, Kant does not regard Hume as
offering a positive explanation of knowledge, but rather
as representing the point of view of thoroughgoing scep-
ticism. But even had he .been acquainted at first hand
with Hume's Treatise^ he would undoubtedly have felt little
sympathy with Hume's naturalistic view of the function of
reason. His training in the mathematical sciences would
have enabled him to detect the inadequacy of Hume's treat-
ment of mathematical knowledge, and his strong moral
convictions would have led him to rebel against the natural-
istic assumptions which underlie Hume's entire position.
The Berkeley- Hume comedy is thus repeated with reversed
roles. Just as Berkeley's anti-materialistic philosophy was
mainly influential as a step towards the naturalism of
Hume, and as such still survives in the philosophies of


John Stuart Mill, Herbert Spencer, Huxley, Mach and Karl
Pearson, so in turn Hume's anti-metaphysical theory of
knowledge was destined to be one of the chief contributory
sources of the German speculative movement.

We may now turn to Hume's treatment of the narrower
problem that of justifying our particular causal judgments.
Hume's attitude towards this question is predetermined by the
more fundamental argument, above stated, which precedes it
in the Treatise, but which is entirely omitted from the corre-
sponding chapters of the Enquiry. As the general principle
of causality is of an irrational character, the same must be
true of those particular judgments which are based upon it.
Much of Hume's argument on this question is, indeed, merely
a restatement of what had already been pointed out by his
predecessors. There is no necessary connection discoverable
between any cause and its effect. This is especially evident
as regards the connection between brain states and mental
experiences. No explanation can be given why a motion
in the brain should produce sensations in the mind, or why
a mental resolution should produce movements in the body.
Such sequences may be empirically verified ; they cannot be
rationally understood. That this likewise holds, though in
less obvious fashion, of the causal interrelations of material
bodies, had been emphasised by Geulincx, Malebranche,
Locke, and Berkeley. The fact that one billiard ball should
communicate motion to another by impact is, when examined,
found to be no less incomprehensible than the interaction of
mind and body. Hume, in the following passage, is only
reinforcing this admitted fact, in terms of his own philosophy.

" We fancy that were we brought on a sudden into this world we
could at first have inferred that one billiard ball would communicate
motion to another upon impulse ; and that we needed not to have
waited for the event, in order to pronounce with certainty upon it.
Such is the influence of custom, that, where it is strongest, it not only
covers our natural ignorance, but even conceals itself, arid seems not
to take place merely because it is found in the highest degree." 1

Nor are we conscious of any causal power within the self.
When Berkeley claims that mind has the faculty of producing
images at will, he is really ascribing to it creative agency.
And such creation, as Malebranche had already pointed out,
is not even conceivable.

" I deny that my will produces in me my ideas, for I cannot even
conceive how it could produce them, since my will, not being able

1 Enquiry (Green and Grose), pp. 25-6.


to act or will without knowledge, presupposes my ideas and does not
make them." l " Is there not here," Hume asks, " either in a spiritual
or material substance, or both, some secret mechanism or structure
of parts, upon which the effect depends, and which, being entirely
unknown to us, renders the power or energy of the will equally
unknown and incomprehensible ? " 2

But the fact that Hume thus restates conclusions already
emphasised by his predecessors will not justify us in contend-
ing (as certain historians of philosophy seem inclined to do)
that in his treatment of the causal problem he failed to
make any important advance upon the teaching of the
Occasionalists. Hume was the first to perceive the essential
falsity of the Cartesian, rationalistic view of the causal nexus.
For Descartes, an effect is that which can be deduced with
logical necessity from the concept of its cause. The Occa-
sionalists similarly argued that because natural events can
never be deduced from one another they must in all cases
be due to supernatural agency ; like Descartes, they one
and all failed to comprehend that since by an effect we
mean that which follows in time upon its cause, and since,
therefore, the principle of causality is the law of change,
the nature of causality cannot be expressed in logical terms.
Hume was the first to appreciate the significance of this
fundamental fact; and an entirely new set of problems at
once came into view. If causal connection is not, as previous
thinkers had believed, logical in character, if it does not
signify logical dependence of the so-called effect upon its
cause, its true connotation must lie elsewhere ; and until this
has been traced to its hidden source, any attempted solution
of metaphysical problems is certain to involve many false
assumptions. The answer that is given to the problem of
the origin and content of the causal concept must deter-
mine our interpretation alike of sense-experience and of pure

The problem presents on examination, however, a most
paradoxical aspect. As Hume has already shown, every
effect is an event distinct from its cause, and there is never
any connection, beyond that of mere sequence, discover-
able between them. We observe only sequence ; we assert
necessary connection. What, then, is in our minds when this
latter assertion is made ? And how, if the notion of necessitated
connection cannot be gained through observation of the ex-
ternal events, is it acquired by us? Hume again propounds

1 Eclaircissement sur chap. iii. pt. ii. liv. vi. de la Recherche', tome iv. (1712)
p. 381. 3 Enquiry, p. 57.


a naturalistic solution. Causation, i.e. necessitated sequence
in time, is not in any sense a conception ; it is not a compre-
hended relation between events, but a misunderstood feeling
in our minds. We cannot form any, even the most remote,
conception of how one event can produce another. Neither
imagination nor pure thought, however freely they may act,
are capable of inventing any such notion. But nature, by
the manner in which it has constituted our minds, deludes us
into the belief that we are in actual possession of this idea.
The repeated sequence of events, in fixed order, generates in
us the feeling of a tendency to pass from the perception or
idea of the one to the idea of the other. This feeling, thus
generated by custom, and often in somewhat confused fashion
combined with the feeling of * animal nisus/ which is ex-
perienced in bodily effort, is mistaken by the mind for a
definite concept of force, causality, necessary connection. As
mere feeling it can afford no insight into the relation holding
between events, and as merely subjective can justify no in-
ference in regard to that relation. The terms force, causality,
necessitated sequence in time, have a practical value, as names
for our instinctive, natural expectations; but when employed
as instruments for the theoretical interpretation of experience,
they lead us off on a false trail.

Online LibraryNorman Kemp SmithA commentary to Kant's 'Critique of pure reason,' → online text (page 69 of 72)