The whole of our perception rests a priori on pure intuition (if the perception is regarded as representation, then on time, as the form of our internal intuition), the association of it (the whole) on the pure synthesis of imagination, and our empirical consciousness of it on pure apperception, that is, on the permanent identity of oneself in the midst of all possible representations.
If we wish to follow up the internal ground of this connection of representations to that point towards which they must all converge, and where they receive for the first time that unity of knowledge which is requisite for every possible experience, we must begin with pure apperception. Intuitions are nothing to us, and do not concern us in the least, if they cannot be received into our consciousness, into which they may enter either directly or indirectly. Knowledge is impossible in any other way. We are conscious a priori of our own permanent identity with regard to all representations that can ever belong to our knowledge, as forming a necessary condition of the possibility of all representations (because these could not represent anything in me, unless they belonged with everything else to one consciousness and could at least be connected within it). This principle stands firm a priori, and may be called the transcendental principle of the unity of all the manifold of our representations (therefore also of intuition). This unity of the manifold in one subject is synthetical; the pure apperception therefore supplies us with a principle of the synthetical unity of the manifold in all possible intuitions.4
This synthetical unity, however, presupposes or involves a synthesis, and if that unity is necessary a priori, the synthesis also must be a priori. The transcendental unity of apperception therefore refers to the pure synthesis of imagination as a condition a priori of the possibility of the manifold being united in one knowledge. Now there can take place a priori the productive synthesis of imagination only, because the reproductive rests on conditions of experience. The principle therefore of the necessary unity of the pure (productive) synthesis of imagination, before all apperception, constitutes the ground of the possibility of all knowledge, nay, of all experience.
The synthesis of the manifold in imagination is called transcendental, if, without reference to the difference of intuitions, it affects only the a priori conjunction of the manifold; and the unity of that synthesis is called transcendental if, with reference to the original unity of apperception, it is represented as a priori necessary. As the possibility of all knowledge depends on the unity of that apperception, it follows that the transcendental unity of the synthesis of imagination is the pure form of all possible knowledge through which therefore all objects of possible experience must be represented a priori.
This unity of apperception with reference to the synthesis of imagination is the understanding, and the same unity with reference to the transcendental synthesis of the imagination, the pure understanding. It must be admitted therefore that there exist in the understanding pure forms of knowledge a priori, which contain the necessary unity of the pure synthesis of the imagination in reference to all possible phenomena. These are the categories, that is, the pure concepts of the understanding. The empirical faculty of knowledge of man contains therefore by necessity an understanding which refers to all objects of the senses, though by intuition only, and by its synthesis through imagination, and all phenomena, as data of a possible experience, must conform to that understanding. As this relation of phenomena to a possible experience is likewise necessary, (because, without it, we should receive no knowledge through them, and they would not in the least concern us), it follows that the pure understanding constitutes by the means of the categories a formal and synthetical principle of all experience, and that phenomena have thus a necessary relation to the understanding.
We shall now try to place the necessary connection of the understanding with the phenomena by means of the categories more clearly before the reader, by beginning with the beginning, namely, with the empirical.
The first that is given us is the phenomenon, which, if connected with consciousness, is called perception. (Without its relation to an at least possible consciousness, the phenomenon could never become to us an object of knowledge. It would therefore be nothing to us; and because it has no objective reality in itself, but exists only in being known, it would be nothing altogether.) As every phenomenon contains a manifold, and different perceptions are found in the mind singly and scattered, a connection of them is necessary, such as they cannot have in the senses by themselves. There exists therefore in us an active power for the synthesis of the manifold which we call imagination, and the function of which, as applied to perceptions, I call apprehension.5 This imagination is meant to change the manifold of intuition into an image, it must therefore first receive the impressions into its activity, which I call to apprehend.
It must be clear, however, that even this apprehension of the manifold could not alone produce a coherence of impressions or an image, without some subjective power of calling one perception from which the mind has gone over to another back to that which follows, and thus forming whole series of perceptions. This is the reproductive faculty of imagination which is and can be empirical only.
If representations, as they happen to meet with one another, could reproduce each other at haphazard, they would have no definite coherence, but would form irregular agglomerations only, and never produce knowledge. It is necessary therefore that their reproduction should be subject to a rule by which one representation connects itself in imagination with a second and not with a third. It is this subjective and empirical ground of reproduction according to rules, which is called the association of representations.
If this unity of association did not possess an objective foundation also, which makes it impossible that phenomena should be apprehended by imagination in any other way but under the condition of a possible synthetical unity of that apprehension, it would be a mere accident that phenomena lend themselves to a certain connection in human knowledge. Though we might have the power of associating perceptions, it would still be a matter of uncertainty and chance whether they themselves are associable; and, in case they should not be so, a number of perceptions, nay, the whole of our sensibility, might possibly contain a great deal of empirical consciousness, but in a separate state, nay, without belonging to the one consciousness of myself, which, however, is impossible. Only by ascribing all perceptions to one consciousness (the original apperception) can I say of all of them that I am conscious of them. It must be therefore an objective ground, that is, one that can be understood as existing a priori, and before all empirical laws of imagination, on which alone the possibility, nay, even the necessity of a law can rest, which pervades all phenomena, and which makes us look upon them all, without exception, as data of the senses, associable by themselves, and subject to general rules of a permanent connection in their reproduction. This objective ground of all association of phenomena I call their affinity, and this can nowhere be found except in the principle of the unity of apperception applied to all knowledge which is to belong to me. According to it all phenomena, without exception, must so enter into the mind or be apprehended as to agree with the unity of apperception. This, without a synthetical unity in their connection, which is therefore necessary objectively also, would be impossible.
We have thus seen that the objective unity of all (empirical) consciousness in one consciousness (that of the original apperception) is the necessary condition even of all possible perception, while the affinity of all phenomena (near or remote) is a necessary consequence of a synthesis in imagination which is a priori founded on rules.
Imagination is therefore likewise the power of a synthesis a priori which is the reason why we called it productive imagination, and so far as this aims at nothing but the necessary unity in the synthesis of all the manifold in phenomena, it may be called the transcendental function of imagination. However strange therefore it may appear at first, it must nevertheless have become clear by this time that the affinity of phenomena and
with it their association, and through that, lastly, their reproduction also according to laws, that is, the whole of our experience, becomes possible only by means of that transcendental function of imagination, without which no concepts of objects could ever come together in one experience.
It is the permanent and unchanging Ego (or pure apperception) which forms the correlative of all our representations, if we are to become conscious of them, and all consciousness belongs quite as much to such an all-embracing pure apperception as all sensuous intuitions belongs, as a representation, to a pure internal intuition, namely, time. This apperception it is which must be added to pure imagination, in order to render its function intellectual. For by itself, the synthesis of imagination, though carried out a priori, is always sensuous, and only connects the manifold as it appears in intuition, for instance, the shape of a triangle. But when the manifold is brought into relation with the unity of apperception, concepts which belong to the understanding become possible, but only as related to sensuous intuition through imagination.
We have therefore a pure imagination as one of the fundamental faculties of the human soul, on which all knowledge a priori depends. Through it we bring the manifold of intuition on one side in connection with the condition of the necessary unity of pure apperception on the other. These two extreme ends, sense and understanding, must be brought into contact with each other by means of the transcendental function of imagination, because, without it, the senses might give us phenomena, but no objects of empirical knowledge, therefore no experience. Real experience, which is made up of apprehension, association (reproduction), and lastly recognition of phenomena, contains in this last and highest (among the purely empirical elements of experience) concepts, which render possible the formal unity of experience, and with it, all objective validity (truth) of empirical knowledge. These grounds for the recognition of the manifold, so far as they concern the form only of experience in general, are our categories. On them is founded the whole formal unity in the synthesis of imagination and, through it, of6 the whole empirical use of them (in recognition, reproduction, association, and apprehension) down to the very phenomena, because it is only by means of those elements of knowledge that the phenomena can belong to our consciousness and therefore to ourselves.
It is we therefore who carry into the phenomena which we call nature, order and regularity, nay, we should never find them in nature, if we ourselves, or the nature of our mind, had not originally placed them there. For the unity of nature is meant to be a necessary and a priori certain unity in the connection of all phenomena. And how should we a priori have arrived at such a synthetical unity, if the subjective grounds of such unity were not contained a priori in the original sources of our knowledge, and if those subjective conditions did not at the same time possess objective validity, as being the grounds on which alone an object becomes possible in our experience?
We have before given various definitions of the understanding, by calling it the spontaneity of knowledge (as opposed to the receptivity of the senses), or the faculty of thinking, or the faculty of concepts or of judgments; all of these explanations, if more closely examined, coming to the same. We may now characterise it as the faculty of rules. This characteristic is more significant, and approaches nearer to the essence of the understanding. The senses give us forms (of intuition), the understanding rules, being always busy to examine phenomena, in order to discover in them some kind of rule. Rules, so far as they are objective (therefore necessarily inherent in our knowledge of an object), are called laws. Although experience teaches us many laws, yet these are only particular determinations of higher laws, the highest of them, to which all others are subject, springing a priori from the understanding; not being derived from experience, but, on the contrary, imparting to the phenomena their regularity, and thus making experience possible. The understanding therefore is not only a power of making rules by a comparison of phenomena, it is itself the lawgiver of nature, and without the understanding nature, that is, a synthetical unity of the manifold of phenomena, according to rules, would be nowhere to be found, because phenomena, as such, cannot exist without us, but exist in our sensibility only. This sensibility, as an object of our knowledge in any experience, with everything it may contain, is possible only in the unity of apperception, which unity of apperception is transcendental ground of the necessary order of all phenomena in an experience. The same unity of apperception with reference to the manifold of representations (so as to determine it out of one)7 forms what we call the rule, and the faculty of these rules I call the understanding. As possible experience therefore, all phenomena depend in the same way a priori on the understanding, and receive their formal possibility from it as, when looked upon as mere intuitions, they depend on sensibility, and become possible through it, so far as their form is concerned.
However exaggerated therefore and absurd it may sound, that the understanding is itself the source of the laws of nature, and of its formal unity, such a statement is nevertheless correct and in accordance with experience. It is quite true, no doubt, that empirical laws, as such, cannot derive their origin from the pure understanding, as little as the infinite manifoldness of phenomena could be sufficiently comprehended through the pure form of sensuous intuition. But all empirical laws are only particular determinations of the pure laws of the understanding, under which and according to which the former become possible, and phenomena assume a regular form, quite as much as all phenomena, in spite of the variety of their empirical form, must always submit to the conditions of the pure form of sensibility.
The pure understanding is therefore in the categories the law of the synthetical unity of all phenomena, and thus makes experience, so far as its form is concerned, for the first time possible. This, and no more than this, we were called upon to prove in the transcendental deduction of the categories, namely, to make the relation of the
Summary Representation
Of the Correctness and of the Only Possibility of this Deduction of the Pure Concepts of the Understanding
If the objects with which our knowledge has to deal were things by themselves, we could have no concepts a priori of them. For where should we take them? If we took them from the object (without asking even the question, how that object could be known to us) our concepts would be empirical only, not concepts a priori. If we took them from within ourselves, then that which is within us only, could not determine the nature of an object different from our representations, that is, supply a ground why there should be a thing to which something like what we have in our thoughts really belongs, and why all this representation should not rather be altogether empty. But if, on the contrary, we have to deal with phenomena only, then it becomes not only possible, but necessary, that certain concepts a priori should precede our empirical knowledge of objects. For being phenomena, they form an object that is within us only, because a mere modification of our sensibility can never exist outside us. The very idea that all these phenomena, and therefore all objects with which we have to deal, are altogether within me, or determinations of my own identical self, implies by itself the necessity of a permanent unity of them in one and the same apperception. In that unity of a possible consciousness consists also the form of all knowledge of objects, by which the manifold is thought as belonging to one object. The manner therefore in which the manifold of sensuous representation (intuition) belongs to our consciousness, precedes all knowledge of an object, as its intellectual form, and constitutes a kind of formal a priori knowledge of all objects in general, if they are to be thought (categories). Their synthesis by means of pure imagination, and the unity of all representations with reference to the original apperception, precede all empirical knowledge. Pure concepts of the understanding are therefore a priori possible, nay, with regard to experience, necessary, for this simple reason, because our knowledge has to deal with nothing but phenomena, the possibility of which depends on ourselves, and the connection and unity of which (in the representation
of an object) can be found in ourselves only, as antecedent to all experience, nay, as first rendering all experience possible, so far as its form is concerned. On this ground, as the only possible one, our deduction of the categories has been carried out.]
1 That is a transcendental deduction.
2 Read deren instead of dessen.
3 The last paragraph is omitted in the Second Edition. There is instead a criticism of Locke and Hume, Supplement XIII. The Deduction of the Categories is much changed, as seen in Supplement XIV.
4 This point is of great importance and should be carefully considered. All representations have a necessary relation to some possible empirical consciousness, for if they did not possess that relation, and if it were entirely impossible to become conscious of them, this would be the same as if they did not exist. All empirical consciousness has a necessary relation to a transcendental consciousness, which precedes all single experiences, namely, the consciousness of my own self as the original apperception. It is absolutely necessary therefore that in my knowledge all consciousness should belong to one consciousness of my own self. Here we have a synthetical unity of the manifold (consciousness) which can be known a priori, and which may thus supply a foundation for synthetical propositions a priori concerning pure thinking in the same way as space and time supply a foundation for synthetical propositions which concern the form of mere intuition.
The synthetical proposition that the different kinds of empirical consciousness must be connected in one self-consciousness, is the very first and synthetical foundation of all our thinking. It should be remembered that the mere representation of the Ego in reference to all other representations (the collective unity of which would be impossible without it) constitutes our transcendental consciousness. It does not matter whether that representation is clear (empirical consciousness) or confused, not even whether it is real; but the possibility of the logical form of all knowledge rests necessarily on the relation to this apperception as a faculty.
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