Critique of Pure Reason (Transcendental Deduction -B)

Immanuel Kant's
Critique
trans. by Norman Kemp Smith
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DEDUCTION OF THE PURE CONCEPTS OF THE
UNDERSTANDING
Section 2
TRANSCENDENTAL DEDUCTION OF THE PURE CONCEPTS
OF THE UNDERSTANDING
$15
The Possibility of Combination in General
THE manifold of representations can be given in an intuition
which is purely sensible, that is, nothing but receptivity; and
the form of this intuition can lie a priori in our faculty of
representation, without being anything more than the mode in
which the subject is affected. But the combination (conjunctio)
of a manifold in general can never come to us through the
senses, and cannot, therefore, be already contained in the pure
form of sensible intuition. For it is an act of spontaneity of the
faculty of representation; and since this faculty, to distinguish
it from sensibility, must be entitled understanding, all 
combination -- be we conscious of it or not, be it a combination of
the manifold of intuition, empirical or non-empirical, or of
various concepts -- is an act of the understanding. To this act
the general title 'synthesis' may be assigned, as indicating
that we cannot represent to ourselves anything as combined in
the object which we have not ourselves previously combined,
and that of all representations combination is the only one which
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cannot be given through objects. Being an act of the self-
activity of the subject, it cannot be executed save by the subject
itself. It will easily be observed that this action is originally
one and is equipollent for all combination, and that is 
dissolution, namely, analysis, which appears to be its opposite,
yet always presupposes it. For where the understanding has
not previously combined, it cannot dissolve, since only as
having been combined by the understanding can anything that
allows of analysis be given to the faculty of representation.
 But the concept of combination includes, besides the concept
of the manifold and of its synthesis, also the concept of
the unity of the manifold. Combination is representation of the
synthetic unity of the manifold. The representation of this
unity cannot, therefore, arise out of the combination. On the
contrary, it is what, by adding itself to the representation of
the manifold, first makes possible the concept of the combination.
This unity, which precedes a priori all concepts of combination,
is not the category of unity ($10); for all categories
are grounded in logical functions of judgment, and in these
functions combination, and therefore unity of given concepts,
is already thought. Thus the category already presupposes
combination. We must therefore look yet higher for this unity
(as qualitative, $12), namely in that which itself contains the
ground of the unity of diverse concepts in judgment, and therefore
of the possibility of the understanding, even as regards
its logical employment.
$16
The Original Synthetic Unity of Apperception
 It must be possible for the 'I think' to accompany all my
representations; for otherwise something would be represented
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in me which could not be thought at all, and that is equivalent
to saying that the representation would be impossible, or at
least would be nothing to me.
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 Whether the representations are in themselves identical, and
whether, therefore, one can be analytically thought through the
other, is not a question that here arises. The consciousness of the one,
when the manifold is under consideration, has always to be 
distinguished from the consciousness of the other; and it is with the
synthesis of this (possible) consciousness that we are here alone
concerned.
P 153
That representation which can
be given prior to all thought is entitled intuition. All the
manifold of intuition has, therefore, a necessary relation to the
'I think' in the same subject in which this manifold is found.
But this representation is an act of spontaneity, that is, it
cannot be regarded as belonging to sensibility. I call it pure
apperception, to distinguish it from empirical apperception, or,
again, origninal apperception, because it is that self-consiousness
which, while generating the representation 'I think' (a
representation which must be capable of accompanying all
other representations, and which in all consciousness is one and
the same), cannot itself be accompanied by any further 
representation. The unity of this apperception I likewise entitle the
transcendental unity of self-consciousness, in order to indicate
the possibility of a priori knowledge arising from it. For the
manifold representations, which are given in an intuition,
would not be one and all my representations, if they did
not all belong to one self-consciousness. As my representations
(even if I am not conscious of them as such) they
must conform to the condition under which alone they can
stand together in one universal self-consciousness, because
otherwise they would not all without exception belong to
me. From this original combination many consequences
follow.
 This thoroughgoing identity of the apperception of a
manifold which is given in intuition contains a synthesis of
representations, and is possible only through the consciousness
of this synthesis. For the empirical consciousness, which
accompanies different representations, is in itself diverse and
without relation to the identity of the subject. That relation
comes about, not simply through my accompanying each 
representation with consciousness, but only in so far as I conjoin
one representation with another, and am conscious of the 
synthesis of them. Only in so far, therefore, as I can unite a
manifold of given representations in one consciousness, is it
possible for me to represent to myself the identity of the 
consciousness in [i.e. throughout] these representations. In other
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words, the analytic unity of apperception is possible only under
the presupposition of a certain synthetic unity.
 The thought that the representations given in intuition one
and all belong to me, is therefore equivalent to the thought
that I unite them in one self-consciousness, or can at least
so unite them; and although this thought is not itself the
consciousness of the synthesis of the representations, it 
presupposes the possibility of that synthesis. In other words, only
in so far as I can grasp the manifold of the representations in
one consciousness, do I call them one and all mine. For 
otherwise I should have as many-coloured and diverse a self as I
have representations of which I am conscious to myself. 
Synthetic unity of the manifold of intuitions, as generated a -
priori, is thus the ground of the identity of apperception itself,
which precedes a priori all my determinate thought. Combination
does not, however, lie in the objects, and cannot be
borrowed from them, and so, through perception, first taken up
into the understanding. On the contrary, it is an affair of the
understanding alone, which itself is nothing but the faculty
of combining a priori, and of bringing the manifold of given
representations under the unity of apperception. The principle
of apperception is the highest principle in the whole sphere of
human knowledge.
This principle of the necessary unity of apperception is
++ The analytic unity of consciousness belongs to all general concepts,
as such. If, for instance, I think red in general, I thereby represent
to myself a property which (as a characteristic) can be found in
something, or can he combined with other representations; that is,
only by means of a presupposed possible synthetic unity can I represent
to myself the analytic unity. A representation which is to be
thought as common to different representations is regarded as belonging
to such as have, in addition to it, also something different.
Consequently it must previously be thought in synthetic unity with
other (though, it may be, only possible) representations, before I can
think in it the analytic unity of consciousness, which makes it a 
conceptus communis. The synthetic unity of apperception is therefore
that highest point, to which we must ascribe all employment of the
understanding, even the whole of logic, and conformably therewith,
transcendental philosophy. Indeed this faculty of apperception is the
understanding itself.
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itself, indeed, an identical, and therefore analytic, proposition;
nevertheless it reveals the necessity of a synthesis of the
manifold given in intuition, without which the thoroughgoing
identity of self-consciousness cannot be thought. For through
the 'I', as simple representation, nothing manifold is given;
only in intuition, which is distinct from the 'I', can a manifold
be given; and only through combination in one consciousness
can it be thought. An understanding in which through
self-consciousness all the manifold would eo ipso be given,
would be intuitive; our understanding can only think, and
for intuition must look to the senses. I am conscious of the
self as identical in respect of the manifold of representations
that are given to me in an intuition, because I call them one
and all my representations, and so apprehend them as 
constituting one intuition. This amounts to saying, that I am
conscious to myself a priori of a necessary synthesis of 
representations -- to be entitled the original synthetic unity of
apperception -- under which all representations that are given
to me must stand, but under which they have also first to
be brought by means of a synthesis.
$17
The Principle of the Synthetic Unity is the Supreme
Principle of all Employment of the Understanding
The supreme principle of the possibility of all intuition in
its relation to sensibility is, according to the Transcendental
Aesthetic, that all the manifold of intuition should be subject
to the formal conditions of space and time. The supreme principle
of the same possibility, in its relation to understanding,
is that all the manifold of intuition should be subject to 
conditions of the original synthetic unity of apperception.
 Space and time, and all their parts, are intuitions, and are,
therefore, with the manifold which they contain, singular representations
(vide the Transcendental Aesthetic). Consequently they are not
mere concepts through which one and the same consciousness is
found to be contained in a number of representations. On the 
contrary, through them many representations are found to be contained
in one representation, and in the consciousness of that representation
; and they are thus composite. The unity of that consciousness
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is therefore synthetic and yet is also original. The singularity of such
intuitions is found to have important consequences (vide $25).
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In so
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far as the manifold representations of intuition are given to us,
they are subject to the former of these two principles; in so far
as they must allow of being combined in one consciousness,
they are subject to the latter. For without such combination
nothing can be thought or known, since the given 
representations would not have in common the act of the 
apperception 'I think', and so could not be apprehended together in
knowledge. This knowledge consists in the determinate relation
of given representations to an object; and an object is
that in the concept of which the manifold of a given intuition
is united. Now all unification of representations demands
unity of consciousness in the synthesis of them. Consequently
it is the unity of consciousness that alone constitutes the
relation of representations to an object, and therefore their
objective validity and the fact that they are modes of knowledge;
and upon it therefore rests the very possibility of the
understanding.
The first pure knowledge of understanding, then, upon
which all the rest of its employment is based, and which also
at the same time is completely independent of all conditions
of sensible intuition, is the principle of the original synthetic
unity of apperception. Thus the mere form of outer sensible
intuition, space, is not yet [by itself] knowledge; it supplies
only the manifold of a priori intuition for a possible 
knowledge. To know anything in space (for instance, a line), I
must draw it, and thus synthetically bring into being a 
determinate combination of the given manifold, so that the unity
of this act is at the same time the unity of consciousness (as
in the concept of a line); and it is through this unity of 
consciousness that an object (a determinate space) is first known.
The synthetic unity of consciousness is, therefore, an objective
condition of all knowledge. It is not merely a condition that
I myself require in knowing an object, but is a condition
under which every intuition must stand in order to become
an object for me. For otherwise, in the absence of this
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synthesis, the manifold would not be united in one 
consciousness. 
Although this proposition makes synthetic unity a condition
of all thought, it is, as already stated, itself analytic.
For it says no more than that all my representations in any
given intuition must be subject to that condition under which
alone I can ascribe them to the identical self as my 
representations, and so can comprehend them as synthetically 
combined in one apperception through the general expression,
'I think'.
This principle is not, however, to be taken as applying
to every possible understanding, but only to that understanding
through whose pure apperception, in the representation
'I am', nothing manifold is given. An understanding which
through its self-consciousness could supply to itself the manifold
of intuition -- an understanding, that is to say, through
whose representation the objects of the representation should
at the same time exist -- would not require, for the unity of
consciousness, a special act of synthesis of the manifold. For
the human understanding, however, which thinks only, and
does not intuit, that act is necessary. It is indeed the first
principle of the human understanding, and is so indispensable
to it that we cannot form the least conception of any other
possible understanding, either of such as is itself intuitive or
of any that may possess an underlying mode of sensible intuition
which is different in kind from that in space and time.
$18
The Objective Unity of Self-Consciousness
The transcendental unity of apperception is that unity
through which all the manifold given in an intuition is united
in a concept of the object. It is therefore entitled objective,
and must be distinguished from the subjective unity of 
consciousness, which is a determination of inner sense -- through
which the manifold of intuition for such [objective] combination
is empirically given. Whether I can become empirically
conscious of the manifold as simultaneous or as successive
depends on circumstances or empirical conditions. Therefore
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the empirical unity of consciousness, through association of
representations, itself concerns an appearance, and is wholly
contingent. But the pure form of intuition in time, merely
as intuition in general, which contains a given manifold, is
subject to the original unity of consciousness, simply through
the necessary relation of the manifold of the intuition to
the one 'I think', and so through the pure synthesis of
understanding which is the a priori underlying ground of
the empirical synthesis. Only the original unity is objectively
valid; the empirical unity of apperception, upon which we
are not here dwelling, and which besides is merely derived
from the former under given conditions in concreto, has only
subjective validity. To one man, for instance, a certain word
suggests one thing, to another some other thing; the unity
of consciousness in that which is empirical is not, as regards
what is given, necessarily and universally valid.
$19
The Logical Form of all Judgments consists in the Objective
Unity of the Apperception of the Concepts which they
contain
I have never been able to accept the interpretation which
logicians give of judgment in general. It is, they declare,
the representation of a relation between two concepts. I do
not here dispute with them as to what is defective in this
interpretation -- that in any case it applies only to categorical,
not to hypothetical and disjunctive judgments (the two latter
containing a relation not of concepts but of judgments), an
oversight from which many troublesome consequences have
followed. I need only point out that the definition does not
determine in what the asserted relation consists.
 The lengthy doctrine of the four syllogistic figures concerns
categorical syllogisms only; and although it is indeed nothing more
than an artificial method of securing, through the surreptitious
introduction of immediate inferences (consequentiae immediatae)
among the premisses of a pure syllogism, the appearance that there
are more kinds of inference than that of the first figure, this would
hardly have met with such remarkable acceptance, had not its
authors succeeded in bringing categorical judgments into such
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exclusive respect, as being those to which all others must allow of
being reduced -- teaching which, as indicated in $9, is none the less
erroneous.
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But if I investigate more precisely the relation of the given
modes of knowledge in any judgment, and distinguish it,
as belonging to the understanding, from the relation 
according to laws of the reproductive imagination, which has
only subjective validity, I find that a judgment is nothing
but the manner in which given modes of knowledge are
brought to the objective unity of apperception. This is what
is intended by the copula 'is'. It is employed to distinguish
the objective unity of given representations from the subjective.
It indicates their relation to original apperception,
and its necessary unity. It holds good even if the judgment
is itself empirical, and therefore contingent, as, for example,
in the judgment, 'Bodies are heavy'. I do not here assert that
these representations necessarily belong to one another in the
empirical intuition, but that they belong to one another in
virtue of the necessary unity of apperception in the synthesis
of intuitions, that is, according to principles of the objective
determination of all representations, in so far as knowledge
can be acquired by means of these representations --
principles which are all derived from the fundamental principle
of the transcendental unity of apperception. Only in this
way does there arise from this relation a judgment, that is, a
relation which is objectively valid, and so can be adequately
distinguished from a relation of the same representations
that would have only subjective validity -- as when they are
connected according to laws of association. In the latter case,
all that I could say would be, 'If I support a body, I feel an
impression of weight'; I could not say, 'It, the body, is heavy'.
Thus to say 'The body is heavy' is not merely to state that
the two representations have always been conjoined in my
perception, however often that perception be repeated; what
we are asserting is that they are combined in the object, no
matter what the state of the subject may be.
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$20
All Sensible Intuitions are subject to the Categories, as 
Conditions under which alone their Manifold can come 
together in one Consciousness
The manifold given in a sensible intuition is necessarily
subject to the original synthetic unity of apperception, because
in no other way is the unity of intuition possible ($17).
But that act of understanding by which the manifold of given
representations (be they intuitions or concepts) is brought
under one apperception, is the logical function of judgment
(cf. $19). All the manifold, therefore, so far as it is given in a
single empirical intuition, is determined in respect of one of
the logical functions of judgment, and is thereby brought into
one consciousness. Now the categories are just these functions
of judgment, in so far as they are employed in determination
of the manifold of a given intuition (cf. $13). Consequently,
the manifold in a given intuition is necessarily subject to the
categories.
$21
Observation
A manifold, contained in an intuition which I call mine, is
represented, by means of the synthesis of the understanding, as
belonging to the necessary unity of self-consciousness; and this
is effected by means of the category. This [requirement of a]
category therefore shows that the empirical consciousness of a
given manifold in a single intuition is subject to a pure self-
consciousness a priori, just as is empirical intuition to a pure
sensible intuition, which likewise takes place a priori. Thus in
the above proposition a beginning is made of a deduction of
the pure concepts of understanding;
 The proof of this rests on the represented unity of intuition, by
which an object is given. This unity of intuition always includes in
itself a synthesis of the manifold given for an intuition, and so
already contains the relation of this manifold to the unity of 
apperception. 
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and in this deduction,
since the categories have their source in the understanding
alone, independently of sensibility, I must abstract from the
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mode in which the manifold for an empirical intuition is given,
and must direct attention solely to the unity which, in terms of
the category, and by means of the understanding, enters into
the intuition. In what follows (cf. $26) it will be shown, from
the mode in which the empirical intuition is given in sensibility,
that its unity is no other than that which the category
(according to $20) prescribes to the manifold of a given 
intuition in general. Only thus, by demonstration of the a priori
validity of the categories in respect of all objects of our senses,
will the purpose of the deduction be fully attained.
But in the above proof there is one feature from which I
could not abstract, the feature, namely, that the manifold to be
intuited must be given prior to the synthesis of understanding,
and independently of it. How this takes place, remains here
undetermined. For were I to think an understanding which is
itself intuitive (as, for example, a divine understanding which
should not represent to itself given objects, but through whose
representation the objects should themselves be given or 
produced), the categories would have no meaning whatsoever in
respect of such a mode of knowledge. They are merely rules for
an understanding whose whole power consists in thought, consists,
that is, in the act whereby it brings the synthesis of a manifold,
given to it from elsewhere in intuition, to the unity of 
apperception -- a faculty, therefore, which by itself knows nothing
whatsoever, but merely combines and arranges the material of
knowledge, that is, the intuition, which must be given to it by
the object. This peculiarity of our understanding, that it can
produce a priori unity of apperception solely by means of the
categories, and only by such and so many, is as little capable
of further explanation as why we have just these and no other
functions of judgment, or why space and time are the only
forms of our possible intuition.
$22
The Category has no other Application in Knowledge
than to Objects of Experience
To think an object and to know an object are thus by no
means the same thing. Knowledge involves two factors: first,
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the concept, through which an object in general is thought (the
category); and secondly, the intuition, through which it is
given. For if no intuition could be given corresponding to the
concept, the concept would still indeed be a thought, so far as
its form is concerned, but would be without any object, and no
knowledge of anything would be possible by means of it. So
far as I could know, there would be nothing, and could be
nothing, to which my thought could be applied. Now, as the
Aesthetic has shown, the only intuition possible to us is 
sensible; consequently, the thought of an object in general, by
means of a pure concept of understanding, can become knowledge
for us only in so far as the concept is related to objects
of the senses. Sensible intuition is either pure intuition (space
and time) or empirical intuition of that which is immediately
represented, through sensation, as actual in space and time.
Through the determination of pure intuition we can acquire
a priori knowledge of objects, as in mathematics, but only
in regard to their form, as appearances; whether there can be
things which must be intuited in this form, is still left 
undecided. Mathematical concepts are not, therefore, by themselves
knowledge, except on the supposition that there are things
which allow of being presented to us only in accordance with
the form of that pure sensible intuition. Now things in space
and time are given only in so far as they are perceptions
(that is, representations accompanied by sensation) -- therefore
only through empirical representation. Consequently, the pure
concepts of understanding, even when they are applied to a -
priori intuitions, as in mathematics, yield knowledge only in
so far as these intuitions -- and therefore indirectly by their
means the pure concepts also -- can be applied to empirical 
intuitions. Even, therefore, with the aid of [pure] intuition, the
categories do not afford us any knowledge of things; they do
so only through their possible application to empirical intuition.
In other words, they serve only for the possibility of 
empirical knowledge; and such knowledge is what we entitle
experience. Our conclusion is therefore this: the categories,
as yielding knowledge of things, have no kind of application,
save only in regard to things which may be objects of possible
experience.
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$23
The above proposition is of the greatest importance; for it
determines the limits of the employment of the pure concepts
of understanding in regard to objects, just as the Transcendental
Aesthetic determined the limits of the employment of
the pure form of our sensible intuition. Space and time, as 
conditions under which alone objects can possibly be given to us,
are valid no further than for objects of the senses, and 
therefore only for experience. Beyond these limits they represent
nothing; for they are only in the senses, and beyond them have
no reality. The pure concepts of understanding are free from
this limitation, and extend to objects of intuition in general,
be the intuition like or unlike ours, if only it be sensible and
not intellectual. But this extension of concepts beyond our
sensible intuition is of no advantage to us. For as concepts of
objects they are then empty, and do not even enable us to
judge of their objects whether or not they are possible. They
are mere forms of thought, without objective reality, since
we have no intuition at hand to which the synthetic unity
of apperception, which constitutes the whole content of these
forms, could be applied, and in being so applied determine
an object. Only our sensible and empirical intuition can give
to them body and meaning.
If we suppose an object of a non-sensible intuition to be
given, we can indeed represent it through all the predicates
which are implied in the presupposition that it has none of the
characteristics proper to sensible intuition; that it is not 
extended or in space, that its duration is not a time, that no
change (succession of determinations in time) is to be met with
in it, etc. But there is no proper knowledge if I thus merely 
indicate what the intuition of an object is not, without being able
to say what it is that is contained in the intuition. For I have
not then shown that the object which I am thinking through
my pure concept is even so much as possible, not being in a
position to give any intuition corresponding to the concept,
and being able only to say that our intuition is not applicable to
it. But what has chiefly to be noted is this, that to such a 
something [in general] not a single one of all the categories could
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be applied. We could not, for instance, apply to it the concept
of substance, meaning something which can exist as subject
and never as mere predicate. For save in so far as empirical
intuition provides the instance to which to apply it, I do not
know whether there can be anything that corresponds to such
a form of thought. But of this more hereafter.
$24
The Application of the Categories to Objects of the Senses
in General
The pure concepts of understanding relate, through the
mere understanding, to objects of intuition in general, whether
that intuition be our own or any other, provided only it be
sensible. The concepts are, however, for this very reason, mere
forms of thought, through which alone no determinate object is
known. The synthesis or combination of the manifold in them
relates only to the unity of apperception, and is thereby the
ground of the possibility of a priori knowledge, so far as such
knowledge rests on the understanding. This synthesis, therefore,
is at once transcendental and also purely intellectual. But
since there lies in us a certain form of a priori sensible 
intuition, which depends on the receptivity of the faculty of 
representation (sensibility), the understanding, as spontaneity, is able
to determine inner sense through the manifold of given 
representations, in accordance with the synthetic unity of 
apperception, and so to think synthetic unity of the apperception
of the manifold of a priori sensible intuition -- that being the
condition under which all objects of our human intuition must
necessarily stand. In this way the categories, in themselves
mere forms of thought, obtain objective reality, that is, 
application to objects which can be given us in intuition. These
objects, however, are only appearances, for it is solely of
appearances that we can have a priori intuition.
This synthesis of the manifold of sensible intuition, which
is possible and necessary a priori, may be entitled figurative
synthesis (synthesis speciosa), to distinguish it from the 
synthesis which is thought in the mere category in respect of the
manifold of an intuition in general, and which is entitled
combination through the understanding (synthesis intellectua-
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lis). Both are transcendental, not merely as taking place
a priori, but also as conditioning the possibility of other
a priori knowledge.
But the figurative synthesis, if it be directed merely
to the original synthetic unity of apperception, that is, to
the transcendental unity which is thought in the categories,
must, in order to be distinguished from the merely intellectual
combination, be called the transcendental synthesis of
imagination. Imagination is the faculty of representing in
intuition an object that is not itself present. Now since all our
intuition is sensible, the imagination, owing to the subjective
condition under which alone it can give to the concepts of
understanding a corresponding intuition, belongs to 
sensibility. But inasmuch as its synthesis is an expression of
spontaneity, which is determinative and not, like sense, 
determinable merely, and which is therefore able to determine
sense a priori in respect of its form in accordance with the
unity of apperception, imagination is to that extent a faculty
which determines the sensibility a priori; and its synthesis of
intuitions, conforming as it does to the categories, must be
the transcendental synthesis of imagination. This synthesis is
an action of the understanding on the sensibility; and is
its first application -- and thereby the ground of all its other
applications -- to the objects of our possible intuition. As
figurative, it is distinguished from the intellectual synthesis,
which is carried out by the understanding alone, without the
aid of the imagination. In so far as imagination is spontaneity,
I sometimes also entitle it the productive imagination, to 
distinguish it from the reproductive imagination, whose synthesis
is entirely subject to empirical laws, the laws, namely, of
association, and which therefore contributes nothing to the
explanation of the possibility of a priori knowledge. The 
reproductive synthesis falls within the domain, not of transcendental
philosophy, but of psychology.
* * *
This is a suitable place for explaining the paradox which
must have been obvious to everyone in our exposition of the
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form of inner sense ($6): namely, that this sense represents
to consciousness even our own selves only as we appear to
ourselves, not as we are in ourselves. For we intuit ourselves
only as we are inwardly affected, and this would seem to be
contradictory, since we should then have to be in a passive
relation [of active affection] to ourselves. It is to avoid this
contradiction that in systems of psychology inner sense,
which we have carefully distinguished from the faculty
of apperception, is commonly regarded as being identical
with it.
What determines inner sense is the understanding and its
original power of combining the manifold of intuition, that is,
of bringing it under an apperception, upon which the 
possibility of understanding itself rest. Now the understanding
in us men is not a faculty of intuitions, and cannot,
even if intuitions be given in sensibility, take them up into
itself in such manner as to combine them as the manifold of
its own intuition. Its synthesis, therefore, if the synthesis be
viewed by itself alone, is nothing but the unity of the act,
of which, as an act, it is conscious to itself, even without
[the aid of] sensibility, but through which it is yet able to
determine the sensibility. The understanding, that is to say,
in respect of the manifold which may be given to it in accordance
with the form of sensible intuition, is able to determine
sensibility inwardly. Thus the understanding, under
the title of a transcendental synthesis of imagination, performs
this act upon the passive subject, whose faculty it is, and we
are therefore justified in saying that inner sense is affected
thereby. Apperception and its synthetic unity is, indeed, very
far from being identical with inner sense. The former, as the
source of all combination, applies to the manifold of intuitions
in general, and in the guise of the categories, prior
to all sensible intuition, to objects in general. Inner sense,
on the other hand, contains the mere form of intuition, but
without combination of the manifold in it, and therefore so
far contains no determinate intuition, which is possible only
through the consciousness of the determination of the manifold
by the transcendental act of imagination (synthetic influence
P 167
of the understanding upon inner sense), which I have entitled
figurative synthesis.
This we can always perceive in ourselves. We cannot think
a line without drawing it in thought, or a circle without
describing it. We cannot represent the three dimensions of
space save by setting three lines at right angles to one another
from the same point. Even time itself we cannot represent,
save in so far as we attend, in the drawing of a straight line
(which has to serve as the outer figurative representation of
time), merely to the act of the synthesis of the manifold 
whereby we successively determine inner sense, and in so doing
attend to the succession of this determination in inner sense.
Motion, as an act of the subject (not as a determination of
an object), and therefore the synthesis of the manifold in
space, first produces the concept of succession -- if we abstract
from this manifold and attend solely to the act through which
we determine the inner sense according to its form. The
understanding does not, therefore, find in inner sense such
a combination of the manifold, but produces it, in that it
affects that sense.
How the 'I' that thinks can be distinct from the 'I' that
intuits itself (for I can represent still other modes of intuition
as at least possible), and yet, as being the same subject, can be
identical with the latter; and how, therefore, I can say: "I, as
intelligence and thinking subject, know myself as an object
that is thought, in so far as I am given to myself [as something
other or] beyond that [I] which is [given to myself] in
intuition, and yet know myself, like other phenomena, only
as I appear to myself, not as I am to the understanding" --
these are questions that raise no greater nor less difficulty
than how I can be an object to myself at all, and, more
particularly, an object of intuition and of inner perceptions.
 Motion of an object in space does not belong to a pure science,
and consequently not to geometry. For the fact that something is
movable cannot be known a priori, but only through experience.
Motion, however, considered as the describing of a space, is a pure
act of the successive synthesis of the manifold in outer intuition in
general by means of the productive imagination, and belongs not
only to geometry, but even to transcendental philosophy.
P 168
Indeed, that this is how it must be, is easily shown -- if we
admit that space is merely a pure form of the appearances of
outer sense -- by the fact that we cannot obtain for ourselves
a representation of time, which is not an object of outer 
intuition, except under the image of a line, which we draw, and
that by this mode of depicting it alone could we know the
singleness of its dimension; and similarly by the fact that
for all inner perceptions we must derive the determination of
lengths of time or of points of time from the changes which
are exhibited to us in outer things, and that the determinations
of inner sense have therefore to be arranged as appearances
in time in precisely the same manner in which we
arrange those of outer sense in space. If, then, as regards the
latter, we admit that we know objects only in so far as we
are externally affected, we must also recognise, as regards
inner sense, that by means of it we intuit ourselves only as
we are inwardly affected by ourselves; in other words, that,
so far as inner intuition is concerned, we know our own
subject only as appearance, not as it is in itself.
$25
On the other hand, in the transcendental synthesis of the
manifold of representations in general, and therefore in the
synthetic original unity of apperception, I am conscious of
myself, not as I appear to myself, nor as I am in myself, but
only that I am. This representation is a thought, not an 
intuition. Now in order to know ourselves, there is required in
addition to the act of thought, which brings the manifold
of every possible intuition to the unity of apperception, a 
determinate mode of intuition, whereby this manifold is given;
++ I do not see why so much difficulty should be found in admitting
that our inner sense is affected by ourselves. Such affection finds
exemplification in each and every act of attention. In every act of
attention the understanding determines inner sense, in accordance
with the combination which it thinks, to that inner intuition which
corresponds to the manifold in the synthesis of the understanding.
How much the mind is usually thereby affected, everyone will be
able to perceive in himself.
P 168
it therefore follows that although my existence is not indeed
P 169
appearance (still less mere illusion), the determination of my
existence can take place only in conformity with the form of
inner sense, according to the special mode in which the manifold,
which I combine, is given in inner intuition. Accordingly
I have no knowledge of myself as I am but merely as I appear
to myself. The consciousness of self is thus very far from being
a knowledge of the self, notwithstanding all the categories
which [are being employed to] constitute the thought of an
object in general, through combination of the manifold in one
apperception. Just as for knowledge of an object distinct from
me I require, besides the thought of an object in general
(in the category), an intuition by which I determine that
general concept, so for knowledge of myself I require, besides
the consciousness, that is, besides the thought of myself, an
intuition of the manifold in me, by which I determine this
thought. I exist as an intelligence which is conscious solely
of its power of combination; but in respect of the manifold
which it has to combine I am subjected to a limiting condition
(entitled inner sense), namely, that this combination can be
made intuitable only according to relations of time, which
lie entirely outside the concepts of understanding, strictly 
regarded. Such an intelligence, therefore, can know itself only
as it appears to itself in respect of an intuition which is not
intellectual and cannot be given by the understanding itself,
not as it would know itself if its intuition were intellectual.
++ The 'I think' expresses the act of determining my existence.
Existence is already given thereby, but the mode in which I am to
determine this existence, that is, the manifold belonging to it, is not
thereby given. In order that it be given, self-intuition is required;
and such intuition is conditioned by a given a priori form, namely,
time, which is sensible and belongs to the receptivity of the 
determinable [in me]. Now since I do not have another self-intuition
which gives the determining in me (I am conscious only of the
spontaneity of it) prior to the act of determination, as time does
in the case of the determinable, I cannot determine my existence
as that of a self-active being; all that I can do is to represent to
myself the spontaneity of my thought, that is, of the determination;
and my existence is still only determinable sensibly, that is, as the
existence of an appearance. But it is owing to this spontaneity that
I entitle myself an intelligence.
P 170
$26
Transcendental Deduction of the Universally Possible 
Employment in experience of the Pure Concepts of the
Understanding
In the metaphysical deduction the a priori origin of the
categories has been proved through their complete agreement
with the general logical functions of thought; in the transcendental
deduction we have shown their possibility as a priori
modes of knowledge of objects of an intuition in general
(cf. $$20, 21). We have now to explain the possibility of
knowing a priori, by means of categories, whatever objects
may present themselves to our senses, not indeed in respect
of the form of their intuition, but in respect of the laws of
their combination, and so, as it were, of prescribing laws to
nature, and even of making nature possible. For unless the 
categories discharged this function, there could be no explaining
why everything that can be presented to our senses must be
subject to laws which have their origin a priori in the 
understanding alone.
First of all, I may draw attention to the fact that by 
synthesis of apprehension I understand that combination of the
manifold in an empirical intuition, whereby perception, that
is, empirical consciousness of the intuition (as appearance),
is possible.
In the representations of space and time we have a priori
forms of outer and inner sensible intuition; and to these the
synthesis of apprehension of the manifold of appearance must
always conform, because in no other way can the synthesis
take place at all. But space and time are represented a priori
not merely as forms of sensible intuition, but as themselves
intuitions which contain a manifold [of their own], and 
therefore are represented with the determination of the unity
of this manifold (vide the Transcendental Aesthetic). Thus
P 171
unity of the synthesis of the manifold, without or within us,
and consequently also a combination to which everything that
is to be represented as determined in space or in time must
conform, is given a priori as the condition of the synthesis
of all apprehension -- not indeed in, but with these intuitions.
This synthetic unity can be no other than the unity of the
combination of the manifold of a given intuition in general
in an original consciousness, in accordance with the categories,
in so far as the combination is applied to our sensible
intuition. All synthesis, therefore, even that which renders
perception possible, is subject to the categories; and since
experience is knowledge by means of connected perceptions,
the categories are conditions of the possibility of experience,
and are therefore valid a priori for all objects of experience.
* * *
When, for instance, by apprehension of the manifold of a
house I make the empirical intuition of it into a perception,
the necessary unity of space and of outer sensible intuition in
general lies at the basis of my apprehension, and I draw as it
were the outline of the house in conformity with this synthetic
unity of the manifold in space. But if I abstract from the form
of space, this same synthetic unity has its seat in the 
understanding, and is the category of the synthesis of the homogeneous
in an intuition in general, that is, the category of quantity.
To this category, therefore, the synthesis of apprehension, that
is to say, the perception, must completely conform.
P 170n
++ Space, represented as object (as we are required to do in 
geometry), contains more than mere form of intuition; it also contains
combination of the manifold, given according to the form of sensibility,
in an intuitive representation, so that the form of intuition
gives only a manifold, the formal intuition gives unity of representation.
In the Aesthetic I have treated this unity as belonging merely
P 171n
to sensibility, simply in order to emphasise that it precedes any 
concept, although, as a matter of fact, it presupposes a synthesis which
does not belong to the senses but through which all concepts of
space and time first become possible. For since by its means (in that
the understanding determines the sensibility) space and time are
first given as intuitions, the unity of this a priori intuition belongs to
space and time, and not to the concept of the understanding (cf.
$24).
++ In this manner it is proved that the synthesis of apprehension,
which is empirical, must necessarily be in conformity with the synthesis
of apperception, which is intellectual and is contained in the
category completely a priori. It is one and the same spontaneity,
P 172n
which in the one case, under the title of imagination, and in the other
case, under the title of understanding, brings combination into the
manifold of intuition.
P 172
When, to take another example, I perceive the freezing of
water, I apprehend two states, fluidity and solidity, and these
as standing to one another in a relation of time. But in time,
which I place at the basis of the appearance [in so far] as
[it is] inner intuition, I necessarily represent to myself synthetic
unity of the manifold, without which that relation of time could
not be given in an intuition as being determined in respect of
time-sequence. Now this synthetic unity, as a condition
a priori under which I combine the manifold of an intuition
in general, is -- if I abstract from the constant form of
my inner intuition, namely, time -- the category of cause, by
means of which, when I apply it to my sensibility, I determine
everything that happens in accordance with the relation
which it prescribes, and I do so in time in general. Thus my
apprehension of such an event, and therefore the event itself,
considered as a possible perception, is subject to the concept
of the relation of effects and causes, and so in all other
cases.
Categories are concepts which prescribe laws a priori to
appearances, and therefore to nature, the sum of all appearances
(natura materialiter spectata). The question therefore
arises, how it can be conceivable that nature should have to
proceed in accordance with categories which yet are not 
derived from it, and do not model themselves upon its pattern;
that is, how they can determine a priori the combination of
the manifold of nature, while yet they are not derived from it.
The solution of this seeming enigma is as follows.
 That the laws of appearances in nature must agree with the
understanding and its a priori form, that is, with its faculty
of combining the manifold in general, is no more surprising
than that the appearances themselves must agree with the form
of a priori sensible intuition. For just as appearances do not
exist in themselves but only relatively to the subject in which,
so far as it has senses, they inhere, so the laws do not exist in
the appearances but only relatively to this same being, so far as
it has understanding. Things in themselves would necessarily,
P 173
apart from any understanding that knows them, conform to
laws of their own. But appearances are only representations of
things which are unknown as regards what they may be in
themselves. As mere representations, they are subject to no
law of connection save that which the connecting faculty 
prescribes. Now it is imagination that connects the manifold of
sensible intuition; and imagination is dependent for the unity
of its intellectual synthesis upon the understanding, and for
the manifoldness of its apprehension upon sensibility. All
possible perception is thus dependent upon synthesis of 
apprehension, and this empirical synthesis in turn upon 
transcendental synthesis, and therefore upon the categories. 
Consequently, all possible perceptions, and therefore everything that
can come to empirical consciousness, that is, all appearances
of nature, must, so far as their connection is concerned, be 
subject to the categories. Nature, considered merely as nature in
general, is dependent upon these categories as the original
ground of its necessary conformity to law (natura formaliter
spectata). Pure understanding is not, however, in a position,
through mere categories, to prescribe to appearances any
a priori laws other than those which are involved in a nature
in general, that is, in the conformity to law of all appearances
in space and time. Special laws, as concerning those appearances
which are empirically determined, cannot in their specific
character be derived from the categories, although they are
one and all subject to them. To obtain any knowledge whatsoever
of these special laws, we must resort to experience; but
it is the a priori laws that alone can instruct us in regard to
experience in general, and as to what it is that can be known
as an object of experience.
$27
Outcome of this Deduction of the Concepts of
Understanding
We cannot think an object save through categories; we
cannot know an object so thought save through intuitions
corresponding to these concepts. Now all our intuitions are
sensible; and this knowledge, in so far as its object is given, is
empirical. But empirical knowledge is experience. Conse-
P 174
quently, there can be no a priori knowledge, except of objects
of possible experience.
But although this knowledge is limited to objects of experience,
it is not therefore all derived from experience. The
pure intuitions [of receptivity] and the pure concepts of 
understanding are elements in knowledge, and both are found in us
a priori. There are only two ways in which we can account for
a necessary agreement of experience with the concepts of its
objects: either experience makes these concepts possible or these
concepts make experience possible. The former supposition
does not hold in respect of the categories (nor of pure sensible
intuition); for since they are a priori concepts, and therefore
independent of experience, the ascription to them of an
empirical origin would be a sort of generatio aequivoca. There
remains, therefore, only the second supposition -- a system, as
it were, of the epigenesis of pure reason -- namely, that the 
categories contain, on the side of the understanding, the grounds
of the possibility of all experience in general. How they make
experience possible, and what are the principles of the 
possibility of experience that they supply in their application to
appearances, will be shown more fully in the following chapter
on the transcendental employment of the faculty of judgment.
A middle course may be proposed between the two above
mentioned, namely, that the categories are neither self-thought
first principles a priori of our knowledge nor derived from 
experience, but subjective dispositions of thought, implanted in
us from the first moment of our existence, and so ordered by
our Creator that their employment is in complete harmony
with the laws of nature in accordance with which experience
P 175
proceeds -- a kind of preformation-system of pure reason.
P 174n
++ Lest my readers should stumble at the alarming evil consequences
which may over-hastily be inferred from this statement, I
may remind them that for thought the categories are not limited by
the conditions of our sensible intuition, but have an unlimited field.
It is only the knowledge of that which we think, the determining of
the object, that requires intuition. In the absence of intuition, the
thought of the object may still have its true and useful consequences,
as regards the subject's employment of reason. The use of reason is
not always directed to the determination of an object, that is, to 
knowledge, but also to the determination of the subject and of its volition
-- a use which cannot be here dealt with.
P 175
Apart, however, from the objection that on such an hypothesis
we can set no limit to the assumption of predetermined
dispositions to future judgments, there is this decisive 
objection against the suggested middle course, that the necessity
of the categories, which belongs to their very conception,
would then have to be sacrificed. The concept of cause, for
instance, which expresses the necessity of an event under a
presupposed condition, would be false if it rested only on an
arbitrary subjective necessity, implanted in us, of connecting
certain empirical representations according to the rule of
causal relation. I would not then be able to say that the effect
is connected with the cause in the object, that is to say, 
necessarily, but only that I am so constituted that I cannot think
this representation otherwise than as thus connected. This is
exactly what the sceptic most desires. For if this be the situation,
all our insight, resting on the supposed objective validity
of our judgments, is nothing but sheer illusion; nor would
there be wanting people who would refuse to admit this subjective
necessity, a necessity which can only be felt. Certainly
a man cannot dispute with anyone regarding that which 
depends merely on the mode in which he is himself organised.
Brief Outline of this Deduction
The deduction is the exposition of the pure concepts of the
understanding, and therewith of all theoretical a priori knowledge,
as principles of the possibility of experience -- the principles
being here taken as the determination of appearances in
space and time in general, and this determination, in turn, as
ultimately following from the original synthetic unity of 
apperception, as the form of the understanding in its relation to
space and time, the original forms of sensibility.
I consider the division by numbered paragraphs as necessary
up to this point, because thus far we have had to treat
of the elementary concepts. We have now to give an account
of their employment, and the exposition may therefore 
proceed in continuous fashion, without such numbering.