THE SENSIBILITY AND THE UNDERSTANDING
The distinction between the sensibility and the understanding[1] is
to Kant fundamental both in itself and in relation to the conclusions
which he reaches. An outline, therefore, of this distinction must
precede any statement or examination of the details of his position.
Unfortunately, in spite of its fundamental character, Kant never
thinks of questioning or criticizing the distinction in the form in
which he draws it, and the presence of certain confusions often
renders it difficult to be sure of his meaning.
[1] Cf. B. 1, 29, 33, 74-5, 75, 92-4; M. 1, 18, 21, 45-46,
57.
The distinction may be stated in his own words thus: "There are two
stems of human knowledge, which perhaps spring from a common but to us
unknown root, namely sensibility and understanding."[2] "Our knowledge
springs from two fundamental sources of the mind; the first receives
representations[3] (receptivity for impressions); the second is the
power of knowing an object by means of these representations
(spontaneity of conceptions). Through the first an object is _given_
to us; through the second the object is _thought_ in relation to the
representation (which is a mere determination of the mind). Perception
and conceptions constitute, therefore, the elements of all our
knowledge, so that neither conceptions without a perception in some
way corresponding to them, nor perception without conceptions can
yield any knowledge.... Neither of these qualities has a preference
over the other. Without sensibility no object would be given to us,
and without understanding no object would be thought. Thoughts without
content are empty, perceptions without conceptions are blind. Hence it
is as necessary for the mind to make its conceptions sensuous (i. e.
to add to them the object in perception) as to make its perceptions
intelligible (i. e. to bring them under conceptions). Neither of these
powers or faculties can exchange its function. The understanding
cannot perceive, and the senses cannot think. Only by their union can
knowledge arise."[4]
[2] B. 29, M. 18
[3] For the sake of uniformity _Vorstellung_ has throughout
been translated by 'representation', though sometimes, as in
the present passage, it would be better rendered by
'presentation'.
[4] B. 74-5, M. 45-6.
The distinction so stated appears straightforward and, on the
whole,[5] sound. And it is fairly referred to by Kant as the
distinction between the faculties of perceiving and conceiving or
thinking, provided that the terms perceiving and conceiving or
thinking be taken to indicate a distinction within perception in the
ordinary sense of the word. His meaning can be stated thus: 'All
knowledge requires the realization of two conditions; an individual
must be presented to us in perception, and we as thinking beings must
bring this individual under or recognize it as an instance of some
universal. Thus, in order to judge 'This is a house' or 'That is red'
we need the presence of the house or of the red colour in perception,
and we must 'recognize' the house or the colour, i. e. apprehend the
individual as a member of a certain kind. Suppose either condition
unrealized. Then if we suppose a failure to conceive, i. e. to
apprehend the individual as a member of some kind, we see that our
perception--if it could be allowed to be anything at all--would be
blind i. e. indeterminate, or a mere 'blur'. What we perceived would
be for us as good as nothing. In fact, we could not even say that we
were perceiving. Again, if we suppose that we had merely the
conception of a house, and neither perceived nor had perceived an
individual to which it applied, we see that the conception, being
without application, would be neither knowledge nor an element in
knowledge. Moreover, the content of a conception is derived from
perception; it is only through its relation to perceived individuals
that we become aware of a universal. To know the meaning of 'redness'
we must have experienced individual red things; to know the meaning of
'house' we must at least have had experience of individual men and of
their physical needs. Hence 'conceptions' without 'perceptions' are
void or empty. The existence of conceptions presupposes experience of
corresponding individuals, even though it also implies the activity of
thinking in relation to these individuals.'[6]
[5] Cf. p. 29, note 1.
[6] Kant's account implies that he has in view only empirical
knowledge; in any case it only applies to empirical
conceptions.
Further, it is true to say that as perceiving we are passive; we do
not do anything. This, as has been pointed out, is the element of
truth contained in the statement that objects are _given_ to us. On
the other hand, it may be truly said that as conceiving, in the sense
of bringing an individual under a universal, we are essentially
active. This is presupposed by the notice or attention involved in
perception ordinarily so called, i. e. perception in the full sense
in which it includes conceiving as well as perceiving.[7] Kant,
therefore, is justified in referring to the sensibility as a
'receptivity' and to the understanding as a 'spontaneity'.
[7] This distinction within perception is of course
compatible with the view that the elements so distinguished
are inseparable.
The distinction, so stated, appears, as has been already said,
intelligible and, in the main[8], valid. Kant, however, renders the
elucidation of his meaning difficult by combining with this view of
the distinction an incompatible and unwarranted theory of perception.
He supposes,[9] without ever questioning the supposition, that
perception is due to the operation of things outside the mind, which
act upon our sensibility and thereby produce sensations. On this
supposition, what we perceive is not, as the distinction just stated
implies, the thing itself, but a sensation produced by it.
Consequently a problem arises as to the meaning on this supposition of
the statements 'by the sensibility objects are given to us' and 'by
the understanding they are thought'. The former statement must mean
that when a thing affects us there is a sensation. It cannot mean that
by the sensibility we know that there exists a thing which causes the
sensation, for this knowledge would imply the activity of thinking;
nor can it mean that in virtue of the sensibility the thing itself is
presented to us. The latter statement must mean that when sensation
arises, the understanding judges that there is something causing it;
and this assertion must really be _a priori_, because not dependent
upon experience. Unfortunately the two statements so interpreted are
wholly inconsistent with the account of the functions of the
sensibility and the understanding which has just been quoted.
[8] See p. 29, note 1.
[9] Cf. B. 1, M. 1.
Further, this theory of perception has two forms. In its first form
the theory is physical rather than metaphysical, and is based upon
our possession of physical organs. It assumes that the reality to be
apprehended is the world of space and time, and it asserts that by the
action of bodies upon our physical organs our sensibility is affected,
and that thereby sensations are originated in us. Thereupon a problem
arises. For if the contribution of the sensibility to our knowledge
of the physical world is limited to a succession of sensations,
explanation must be given of the fact that we have succeeded with
an experience confined to these sensations in acquiring knowledge
of a world which does not consist of sensations.[10] Kant, in fact,
in the _Aesthetic_ has this problem continually before him, and
tries to solve it. He holds that the mind, by means of its forms of
perception and its conceptions of the understanding, superinduces upon
sensations, as data, spatial and other relations, in such a way that
it acquires knowledge of the spatial world.
[10] Cf. B. 1 init., M. 1 init.; B. 34, M. 21 sub fin.
An inherent difficulty, however, of this 'physical' theory of
perception leads to a transformation of it. If, as the theory
supposes, the cause of sensation is outside or beyond the mind, it
cannot be known. Hence the initial assumption that this cause is the
physical world has to be withdrawn, and the cause of sensation comes
to be thought of as the thing in itself of which we can know nothing.
This is undoubtedly the normal form of the theory in Kant's mind.
It may be objected that to attribute to Kant at any time the physical
form of the theory is to accuse him of an impossibly crude confusion
between things in themselves and the spatial world, and that he can
never have thought that the cause of sensation, being as it is outside
the mind, is spatial. But the answer is to be found in the fact that
the problem just referred to as occupying Kant's attention in the
_Aesthetic_ is only a problem at all so long as the cause of sensation
is thought of as a physical body. For the problem 'How do we,
beginning with mere sensation, come to know a spatial and temporal
world?' is only a problem so long as it is supposed that the cause of
sensation is a spatial and temporal world or a part of it, and that
this world is what we come to know. If the cause of sensation, as
being beyond the mind, is held to be unknowable and so not known to be
spatial or temporal, the problem has disappeared. Corroboration is
given by certain passages[11] in the _Critique_ which definitely
mention 'the senses', a term which refers to bodily organs, and by
others[12] to which meaning can be given only if they are taken to
imply that the objects which affect our sensibility are not unknown
things in themselves, but things known to be spatial. Even the use of
the plural in the term 'things in themselves' implies a tendency to
identify the unknowable reality beyond the mind with bodies in space.
For the implication that different sensations are due to different
things in themselves originates in the view that different sensations
are due to the operation of different spatial bodies.
[11] E. g. B. 1 init., M. 1 init., and B. 75 fin., M. 46,
lines 12, 13 [for 'the sensuous faculty' should be
substituted 'the senses'].
[12] E. g. B. 42, lines 11, 12; M. 26, line 13; A. 100, Mah.
195 ('even in the absence of the object'). Cf. B. 182-3, M.
110-1 (see pp. 257-8, and note p. 257), and B. 207-10, M.
126-8 (see pp. 263-5).
It is now necessary to consider how the distinction between the
sensibility and the understanding contributes to articulate the
problem 'How are _a priori_ synthetic judgements possible?' As has
been pointed out, Kant means by this question, 'How is it possible
that the mind is able, in virtue of its own powers, to make universal
and necessary judgements which anticipate its experience of objects?'
To this question his general answer is that it is possible and only
possible because, so far from ideas, as is generally supposed, having
to conform to things, the things to which our ideas or judgements
relate, viz. phenomena, must conform to the nature of the mind. Now,
if the mind's knowing nature can be divided into the sensibility and
the understanding, the problem becomes 'How is it possible for the
mind to make such judgements in virtue of its sensibility and its
understanding?' And the answer will be that it is possible because the
things concerned, i. e. phenomena, must conform to the sensibility and
the understanding, i. e. to the mind's perceiving and thinking nature.
But both the problem and the answer, so stated, give no clue to the
particular _a priori_ judgements thus rendered possible nor to the
nature of the sensibility and the understanding in virtue of which we
make them. It has been seen, however, that the judgements in question
fall into two classes, those of mathematics and those which form the
presuppositions of physics. And it is Kant's aim to relate these
classes to the sensibility and the understanding respectively. His
view is that mathematical judgements, which, as such, deal with
spatial and temporal relations, are essentially bound up with our
perceptive nature, i. e. with our sensibility, and that the principles
underlying physics are the expression of our thinking nature, i. e. of
our understanding. Hence if the vindication of this relation between
our knowing faculties and the judgements to which they are held to
give rise is approached from the side of our faculties, it must be
shown that our sensitive nature is such as to give rise to
mathematical judgements, and that our understanding or thinking nature
is such as to originate the principles underlying physics. Again, if
the account of this relation is to be adequate, it must be shown to be
exhaustive, i. e. it must be shown that the sensibility and the
understanding give rise to no other judgements. Otherwise there may be
other _a priori_ judgements bound up with the sensibility and the
understanding which the inquiry will have ignored. Kant, therefore, by
his distinction between the sensibility and the understanding, sets
himself another problem, which does not come into sight in the first
formulation of the general question 'How are _a priori_ synthetic
judgements possible?' He has to determine what _a priori_ judgements
are related to the sensibility and to the understanding respectively.
At the same time the distinction gives rise to a division within the
main problem. His chief aim is to discover how it is that _a priori_
judgements are universally applicable. But, as Kant conceives
the issue, the problem requires different treatment according
as the judgements in question are related to the sensibility or
to the understanding. Hence arises the distinction between the
_Transcendental Aesthetic_ and the _Transcendental Analytic_, the
former dealing with the _a priori_ judgements of mathematics, which
relate to the sensibility, and the latter dealing with the _a priori_
principles of physics, which originate in the understanding. Again,
within each of these two divisions we have to distinguish two
problems, viz. 'What _a priori_ judgements are essentially related to
the faculty in question?' and 'How is it that they are applicable to
objects?'
It is important, however, to notice that the distinction between the
sensibility and the understanding, in the form in which it serves as a
basis for distinguishing the _Aesthetic_ and the _Analytic_, is not
identical with or even compatible with the distinction, as Kant states
it when he is considering the distinction in itself and is not
thinking of any theory which is to be based upon it. In the latter
case the sensibility and the understanding are represented as
inseparable faculties involved in _all_ knowledge.[13] Only from the
union of both can knowledge arise. But, regarded as a basis for the
distinction between the _Aesthetic_ and the _Analytic_, they are
implied to be the source of different kinds of knowledge, viz.
mathematics and the principles of physics. It is no answer to this to
urge that Kant afterwards points out that space as an object
presupposes a synthesis which does not belong to sense. No doubt this
admission implies that even the apprehension of spatial relations
involves the activity of the understanding. But the implication is
really inconsistent with the existence of the _Aesthetic_ as a
distinct part of the subject dealing with a special class of _a
priori_ judgements.
[13] B. 74-5, M. 45-6; cf. pp. 27-9.
[14] B. 160 note, M. 98 note.