§ 17
The Principle of the Synthetical Unity of Apperception is the Highest Principle of all Employment of the Understanding
The highest principle of the possibility of all intuition, in relation to sensibility, was, according to the transcendental Æsthetic, that all the manifold in it should be subject to the formal conditions of space and time. The highest principle of the same possibility in relation to the understanding is, that all the manifold in intuition must be subject to the conditions of the original synthetical unity of apperception.15
All the manifold representations of intuition, so far as they are given us, are subject to the former, so far as they must admit of being connected in one consciousness, to the latter; and without that nothing can be thought or known by them, because the given representations would not share the act of apperception (I think) in common, and could not be comprehended in one self-consciousness.
The understanding in its most general sense is the faculty of cognitions. These consist in a definite relation of given representations to an object; and an object is that in the concept of which the manifold of a given intuition is connected. All such connection of representations requires of course the unity of the consciousness in their synthesis: consequently, the unity of consciousness is that which alone constitutes the relation of representations to an object, that is, their objective validity, and consequently their becoming cognitions, so that the very possibility of the understanding depends on it.
The first pure cognition of the understanding, therefore, on which all the rest of its employment is founded, and which at the same time is entirely independent of all conditions of sensuous intuition, is this very principle of the original synthetical unity of apperception. Space, the mere form of external sensuous intuition, is not yet cognition: it only supplies the manifold of intuition a priori for a possible cognition. In order to know anything in space, for instance, a line, I must draw it, and produce synthetically a certain connection of the manifold that is given, so that the unity of that act is at the same time the unity of the consciousness (in the concept of a line), and (so that) an object (a determinate space) is then only known for the first time. The synthetical unity of consciousness is, therefore, an objective condition of all knowledge; a condition, not necessary for myself only, in order to know an object, but one to which each intuition must be subject, in order to become an object for me, because the manifold could not become connected in one consciousness in any other way, and without such a synthesis.
No doubt, that proposition, as I said before, is itself analytical, though it makes synthetical unity a condition of all thought, for it really says no more than that all my representations in any given intuition must be subject to the condition under which alone I can ascribe them, as my representations, to the identical self, and therefore comprehend them, as synthetically connected, in one apperception through the general expression, I think.
And yet this need not be a principle for every possible understanding, but only for that which gives nothing manifold through its pure apperception in the representation, I am. An understanding which through its self-consciousness could give the manifold of intuition, and by whose representation the objects of that representation should at the same time exist, would not require a special act of the synthesis of the manifold for the unity of its consciousness, while the human understanding, which possesses the power of thought only, but not of intuition, requires such an act. To the human understanding that first principle is so indispensable that it really cannot form the least concept of any other possible understanding, whether it be intuitive by itself, or possessed of a sensuous intuition, different from that in space and time.
§ 18
What is the Objective Unity of Self-consciousness?
The transcendental unity of apperception connects all the manifold given in an intuition into a concept of an object. It is therefore called objective, and must be distinguished from the subjective unity of consciousness, which is a form of the internal sense, by which the manifold of intuition is empirically given, to be thus connected. Whether I can become empirically conscious of the manifold, as either simultaneous or successive, depends on circumstances, or empirical conditions. The empirical unity of consciousness, therefore, through the association of representations, is itself phenomenal and wholly contingent, while the pure form of intuition in time, merely as general intuition containing the manifold that is given, is subject to the original unity of the consciousness, through the necessary relation only of the manifold of intuition to the one, I think,—that is, through the pure synthesis of the understanding, which forms the a priori ground of the empirical synthesis. That unity alone is, therefore, valid objectively; the empirical unity of apperception, which we do not consider here, and which is only derived from the former, under given conditions in concreto, has subjective validity only. One man connects the representation of a word with one thing, another with another, and the unity of consciousness, with regard to what is empirical, is not necessary nor universally valid with reference to that which is given.
§ 19
The Logical Form of all Judgments consists in the Objective Unity of Apperception of the Concepts contained therein
I could never feel satisfied with the definition of a judgment in general, given by our logicians, who say that it is the representation of a relation between two concepts. Without disputing with them in this place as to the defect of that explanation, that it may possibly apply to categorical, but not to hypothetical and disjunctive judgments (the latter containing, not a relation of concepts, but of judgments themselves),—though many tedious consequences have arisen from this mistake of logicians,—I must at least make this observation, that we are not told in what that relation consists.16
But, if I examine more closely the relation of given cognitions in every judgment, and distinguish it, as belonging to the understanding, from the relation according to the rules of reproductive imagination (which has subjective validity only), I find that a judgment is nothing but the mode of bringing given cognitions into the objective unity of apperception. This is what is intended by the copula is, which is meant to distinguish the objective unity of given representations from the subjective. It (the copula is) indicates their relation to the original apperception, and their necessary unity, even though the judgment itself be empirical, and therefore contingent; as, for instance, bodies are heavy. By this I do not mean to say that these representations belong necessarily to each other, in the empirical intuition, but that they belong to each other by means of the necessary unity of apperception in the synthesis of intuitions, that is, according to the principles of the objective determination of all representations, so far as any cognition is to arise from them, these principles being all derived from the principle of the transcendental unity of apperception. Thus, and thus alone, does the relation become a judgment, that is, a relation that is valid objectively, and can thus be kept sufficiently distinct from the relation of the same representations, if it has subjective validity only, for instance, according to the laws of association. In the latter case, I could only say, that if I carry a body I feel the pressure of its weight, but not, that it, the body, is heavy, which is meant to say that these two representations are connected together in the object, whatever the state of the subject may be, and not only associated or conjoined in the perception, however often it may be repeated.
§ 20
All Sensuous Intuitions are subject to the Categories as to Conditions under which alone their Manifold Contents can come together in one Consciousness
The manifold which is given us in a sensuous intuition is necessarily subject to the original synthetical unity of apperception, because by it alone the unity of intuition becomes possible (§ 7). That act of the understanding, further, by which the manifold of given representations (whether intuitions or concepts) is brought under one apperception in general, is the logical function of a judgment (§ 19). The manifold, therefore, so
far as it is given in an empirical intuition, is determined with regard to one of the logical functions of judgment, by which, indeed, it is brought to consciousness in general. The categories, however, are nothing but these functions of judgment, so far as the manifold of a give intuition is determined with respect to them (§ 13, see p. 84). Therefore the manifold in any given intuition is naturally subject to the categories.
§ 21
Note
The manifold, contained in an intuition which I call my own, is represented through the synthesis of the understanding, as belonging to the necessary unity of self-consciousness, and this takes place through the category.17
This category indicates, therefore, that the empirical consciousness of the manifold, given in any intuition, is subject to a pure self-consciousness a priori, in the same manner as the empirical intuition is subject to a pure sensuous intuition which likewise takes place a priori.
In the above proposition a beginning is made of a deduction of the pure concepts of the understanding. In this deduction, as the categories arise in the understanding only, independent of all sensibility, I ought not yet to take any account of the manner in which the manifold is given for an empirical intuition, but attend exclusively to the unity which, by means of the category, enters into the intuition through the understanding. In what follows (§ 26) we shall show, from the manner in which the empirical intuition is given in sensibility, that its unity is no other than that which is prescribed by the category (according to § 20) to the manifold of any given intuition. Thus only, that is, by showing their validity a priori with respect to all objects of our senses, the purpose of our deduction will be fully attained.
There is one thing, however, of which, in the above demonstration, I could not make abstraction: namely, that the manifold for an intuition must be given antecedently to the synthesis of the understanding, and independently of it;—how, remains uncertain. For if I were to imagine an understanding, itself intuitive (for instance, a divine understanding, which should not represent to itself given objects, but produce them at once by his representation), the categories would have no meaning with respect to such cognition. They are merely rules for an understanding whose whole power consists in thinking, that is, in the act of bringing the synthesis of the manifold, which is given to it in intuition from elsewhere, to the unity of apperception; an understanding which therefore knows nothing by itself, but connects only and arranges the material for cognition, that is, the intuition which must be given to it by the object. This peculiarity of our understanding of producing unity of apperception a priori by means of the categories only, and again by such and so many, cannot be further explained, any more than why we have these and no other functions of judgment, and why time and space are the only forms of a possible intuition for us.
§ 22
The Category admits of no other Employment for the Cognition of Things, but its Application to Objects of Experience
We have seen that to think an object is not the same as to know an object. In order to know an object, we must have the concept by which any object is thought (the category), and likewise the intuition by which it is given. If no corresponding intuition could be given to a concept, it would still be a thought, so far as its form is concerned: but it would be without an object, and no knowledge of anything would be possible by it, because, so far as I know, there would be nothing, and there could be nothing, to which my thought could be referred. Now the only possible intuition for us is sensuous (see Æsthetic); the thought of any object, therefore, by means of a pure con`cept of the understanding, can with us become knowledge only, if it is referred to objects of the senses. Sensuous intuition is either pure (space and time), or empirical, i.e. if it is an intuition of that which is represented in space and time, through sensation as immediately real. By means of pure intuition we can gain knowledge a priori of things as phenomena (in mathematics), but only so far as their form is concerned; but whether there are things which must be perceived, according to that form, remains unsettled. Mathematical concepts, by themselves, therefore, are not yet knowledge, except under the supposition that there are things which admit of being represented by us, according to the form of that pure sensuous intuition only. Consequently, as things in space and time are only given as perceptions (as representations accompanied by sensations), that is, through empirical representations, the pure concepts of the understanding, even if applied to intuitions a priori, as in mathematics, give us knowledge in so far only as these pure intuitions, and therefore through them the concepts of the understanding also, can be applied to empirical intuitions. Consequently the categories, by means of intuition, do not give us any knowledge of things, except under the supposition of their possible application to empirical intuition; they serve, in short, for the possibility of empirical knowledge only, which is called experience. From this it follows that the categories admit of no other employment for the cognition of things, except so far only as these are taken as objects of possible experience.
§ 23
The foregoing proposition is of the greatest importance, for it determines the limits of the employment of the pure concepts of the understanding with reference to objects, in the same manner as the transcendental Æsthetic determined the limits of the employment of the pure form of our sensuous intuition. Space and time are conditions of the possibility of how objects can be given to us, so far only as objects of the senses, therefore of experience, are concerned. Beyond these limits they represent nothing, for they belong only to the senses, and have no reality beyond them. Pure concepts of the understanding are free from this limitation, and extend to objects of intuition in general, whether that intuition be like our own or not, if only it is sensuous and not intellectual. This further extension, however, of concepts beyond our sensuous intuition, is of no avail to us; for they are in that case empty concepts of objects, and the concepts do not even enable us to say, whether such objects be possible or not. They are mere forms of thought, without objective reality: because we have no intuition at hand to which the synthetical unity of apperception, which is contained in the concepts alone, could be applied, so that they might determine an object. Nothing can give them sense and meaning, except our sensuous and empirical intuition.
If, therefore, we assume an object of a non-sensuous intuition as given, we may, no doubt, determine it through all the predicates, which follow from the supposition that nothing belonging to sensuous intuition belongs to it, that, therefore, it is not extended, or not in space, that its duration is not time, that no change (succession of determinations in time) is to be met in it, etc. But we can hardly call this knowledge, if we only indicate how the intuition of an object is not, without being able to say what is contained in it, for, in that case, I have not represented the possibility of an object, corresponding to my pure concept of the understanding, because I could give no intuition corresponding to it, but could only say that our intuition did not apply to it. But what is the most important is this, that not even a single category could be applied to such a thing; as, for instance, the concept of substance, that is, of something that can exist as a subject only, but never as a mere predicate. For I do not know whether there can be anything corresponding to such a determination of thought, unless empirical intuition supplies the case for its application. Of this more hereafter.
§ 24
Of the Application of the Categories to Objects of the Senses in General
The pure concepts of the understanding refer, through the mere understanding, to objects of intuition, whether it be our own, or any other, if only sensuous intuition, but they are, for that very reason, mere forms of thought, by which no definite object can be known. The synthesis, or connection of the manifold in them, referred only to the unity of apperception, and became thus the ground of the possibility of knowledge a priori, so far as it rests on the understanding, and is therefore not only transcendental, but also purely intellectual. Now as there exists in us a certain form of sensuous int
uition a priori, which rests on the receptivity of the faculty of representation (sensibility), the understanding, as spontaneity, is able to determine the internal sense through the manifold of given representations, according to the synthetical unity of apperception, and can thus think synthetical unity of the apperception of the manifold of sensuous intuition a priori, as the condition to which all objects of our (human) intuition must necessarily be subject. Thus the categories, though pure forms of thought, receive objective reality, that is, application to objects which can be given to us in intuition, but as phenomena only; for it is with reference to them alone that we are capable of intuition a priori.
This synthesis of the manifold of sensuous intuition, which is possible and necessary a priori, may be called figurative (synthesis speciosa), in order to distinguish it from that which is thought in the mere category, with reference to the manifold of an intuition in general, and is called intellectual synthesis (synthesis intellectualis). Both are transcendental, not only because they themselves are carried out a priori, but because they establish also the possibility of other knowledge a priori.
But this figurative synthesis, if it refers to the original synthetical unity of apperception only, that is, to that transcendental unity which is thought in the categories, must be called the transcendental synthesis of the faculty of imagination, in order thus to distinguish it from the purely intellectual synthesis. Imagination is the faculty of representing an object even without its presence in intuition. As all our intuition is sensuous, the faculty of imagination belongs, on account of the subjective condition under which alone it can give a corresponding intuition to the concepts of the understanding, to our sensibility. As, however, its synthesis is an act of spontaneity, determining, and not, like the senses, determinable only, and therefore able to determine a priori the senses, so far as their form is concerned, according to the unity of apperception, the faculty of imagination is, so far, a faculty of determining our sensibility a priori, so that the synthesis of the intuitions, according to the categories, must be the transcendental synthesis of the faculty of imagination. This is an effect, produced by the understanding on our sensibility, and the first application of it (and at the same time the ground of all others) to objects of the intuition which is only possible to us. As figurative, it is distinguished from the intellectual synthesis, which takes place by the understanding only, without the aid of the faculty of imagination. In so far as imagination is spontaneity, I call it occasionally productive imagination: distinguishing it from the reproductive, which in its synthesis is subject to empirical laws only, namely, those of association, and which is of no help for the explanation of the possibility of knowledge a priori, belonging, therefore, to psychology, and not to transcendental philosophy.
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