Critique of Pure Reason

by Immanuel Kant

  Therefore the Soul is a person.

  Criticism of the Third Paralogism of Transcendental Psychology

  Whenever I want to know by experience the numerical identity of an external object, I shall have to attend to what is permanent in that phenomenon to which, as the subject, everything else refers as determination, and observe the identity of the former during the time that the latter is changing. I myself, however, am an object of the internal sense, and all time is but the form of the internal sense. I therefore refer each and all of my successive determinations to the numerically identical self; and this in all time, that is, in the form of the inner intuition of myself. From this point of view, the personality of the soul should not even be considered as inferred, but as an entirely identical proposition of self-consciousness in time, and that is indeed the reason why it is valid a priori. For it really says no more than this: that during the whole time, while I am conscious of myself, I am conscious of that time as belonging to the unity of myself; and it comes to the same thing whether I say that this whole time is within me as an individual unity, or that I with numerical identity am present in all that time.

  In my own consciousness, therefore, the identity of person is inevitably present. But if I consider myself from the point of view of another person (as an object of his external intuition), then that external observer considers me, first of all, in time, for in the apperception time is really represented in me only. Though he admits, therefore, the I, which at all times accompanies all representations in my consciousness, and with entire identity, he will not yet infer from it the objective permanence of myself. For as in that case the time in which the observer places me is not the time of my own, but of his sensibility, it follows that the identity which is connected with my consciousness is not therefore connected with his, that is, with the external intuition of my subject.

  The identity of my consciousness at different times is therefore a formal condition only of my thoughts and their coherence, and proves in no way the numerical identity of my subject, in which, in spite of the logical identity of the I, such a change may have passed as to make it impossible to retain its identity, though we may still attribute to it the same name of I, which in every other state, and even in the change of the subject, might yet retain the thought of the preceding and hand it over to the subsequent subject.5

  Although the teaching of some old schools that everything is in a flux, and nothing in the world permanent, cannot be admitted, if we admit substances, yet it must not be supposed that it can be refuted by the unity of self-consciousness. For we ourselves cannot judge from our own consciousness whether, as souls, we are permanent or not, because we reckon as belonging to our own identical self that only of which we are conscious, and therefore are constrained to admit that, during the whole time of which we are conscious, we are one and the same. From the point of view of a stranger, however, such a judgment would not be valid, because, perceiving in the soul no permanent phenomena, except the representation of the I, which accompanies and connects them all, we cannot determine whether that I (being a mere thought) be not in the same state of flux as the other thoughts which are chained together by the I.

  It is curious, however, that the personality and what is presupposed by it, namely, the permanence and substantiality of the soul, has now to be proved first. For if we could presuppose these, there would follow, if not the permanence of consciousness, yet the possibility of a permanent consciousness in one and the same subject, and this is sufficient to establish personality which does not cease at once, because its effect is interrupted at the time. This permanence, however, is by no means given us before the numerical identity of ourself, which we infer from identical apperception, but is itself inferred from it, so that, according to rule, the concept of substance, which alone is empirically useful, would have to follow first upon it. But as the identity of person follows by no means from the identity of the I, in the consciousness of all time in which I perceive myself, it follows that we could not have founded upon it the substantiality of the soul.

  Like the concept of substance and of the simple, however, the concept of personality also may remain, so long as it is used as transcendental only, that is, as a concept of the unity of the subject which is otherwise unknown to us, but in the determinations of which there is an uninterrupted connection by apperception. In this sense such a concept is necessary for practical purposes and sufficient, but we can never pride ourselves on it as helping to expand our knowledge of our self by means of pure reason, which only deceives us if we imagine that we can concluse an uninterrupted continuance of the subject from the mere concept of the identical self. That concept is only constantly turning round itself in a circle, and does not help us as with respect to any question which aims at synthetical knowledge. What matter may be as a thing by itself (a transcendental object) is entirely unknown to us; though we may observe its permanence as a phenomenon, since it is represented as something external. When however I wish to observe the mere I during the change of all representations, I have no other correlative for my comparisons but again the I itself, with the general conditions of my consciousness. I cannot therefore give any but tautological answers to all questions, because I put my concept and its unity in the place of the qualities that belong to me as an object, and thus really take for granted what was wished to be known.

  The Fourth Paralogism of Ideality (with Regard to External Relations)

  That, the existence of which can only be inferred as a cause of given perceptions, has a doubtful existence only:—

  All external phenomena are such that their existence cannot be perceived immediately, but that we can only infer them as the cause of given perceptions:—

  Therefore the existence of all objects of the external senses is doubtful. This uncertainty I call the ideality of external phenomena, and the doctrine of that ideality is called idealism; in comparison with which the other doctrine, which maintains a possible certainty of the objects of the external senses, is called dualism.

  Criticism of the Fourth Paralogism of Transcendental Psychology

  We shall first have to examine the premisses. We are perfectly justified in maintaining that that only which is within ourselves can be perceived immediately, and that my own existence only can be the object of a mere perception. The existence of a real object therefore outside me (taking this word in its intellectual meaning) can never be given directly in perception, but can only be added in thought to the perception, which is a modification of the internal sense, and thus inferred as its external cause. Hence Cartesius was quite right in limiting all perception, in the narrowest sense, to the proposition, I (as a thinking being) am. For it must be clear that, as what is without is not within me, I cannot find it in my apperception; nor hence in any perception which is in reality a determination of apperception only.

  In the true sense of the word, therefore, I can never perceive external things, but only from my own internal perception infer their existence, taking the perception as an effect of which something external must be the proximate cause. An inference, however, from a given effect to a definite cause is always uncertain, because the effect may be due to more than one cause. Therefore in referring a perception to its cause, it always remains doubtful whether that cause be internal or external; whether in fact all so-called external perceptions are not a mere play of our external sense, or point to real external objects as their cause. At all events the existence of the latter is inferential only, and liable to all the dangers of inferences, while the object of the internal sense (I myself with all my representations) is perceived immediately, and its existence cannot be questioned.

  It must not be supposed, therefore, that an idealist is he who denies the existence of external objects of the senses; all he does is to deny that it is known by immediate perception, and to infer that we can never become perfectly certain of their reality by any experience whatsoever.

  Before I expose the deceptive illusion of our p
aralogism, let me remark that we must necessarily distinguish two kinds of idealism, the transcendental and the empirical. Transcendental idealism teaches that all phenomena are representations only, not things by themselves, and that space and time therefore are only sensuous forms of our intuition, not determinations given independently by themselves or conditions of objects, as things by themselves. Opposed to this transcendental idealism, is a transcendental realism, which considers space and time as something in itself (independent of our sensibility). Thus the transcendental realist represents all external phenomena (admitting their reality) as things by themselves, existing independently of us and our sensibility, and therefore existing outside us also, if regarded according to pure concepts of the understanding. It is this transcendental realist who afterwards acts the empirical idealist, and who, after wrongly supposing that the objects of the senses, if they are to be external, must have an existence by themselves, and without our senses, yet from this point of view considers all our sensuous representations insufficient to render certain the reality of their objects.

  The transcendental idealist, on the contrary, may well be an empirical realist, or, as he is called, a dualist; that is, he may admit the existence of matter, without taking a step beyond mere self-consciousness, or admitting more than the certainty of representations within me, that is the cogito, ergo sum. For as he considers matter, and even its internal possibility, as a phenomenon only, which, if separated from our sensibility, is nothing, matter with him is only a class of representations (intuition) which are called external, not as if they referred to objects external by themselves, but because they refer perceptions to space, in which everything is outside everything else, while space itself is inside us.

  We have declared ourselves from the very beginning in favour of this transcendental idealism. In our system, therefore, we need not hesitate to admit the existence of matter on the testimony of mere self-consciousness, and to consider it as established by it (i.e. the testimony), in the same manner as the existence of myself, as a thinking being. I am conscious of my representations, and hence they exist as well as I myself, who has these representations. External objects, however (bodies), are phenomena only, therefore nothing but a class of my representations, the objects of which are something by means of these representations only, and apart from them nothing. External things, therefore, exist by the same right as I myself, both on the immediate testimony of my self-consciousness, with this difference only, that the representation of myself, as a thinking subject, is referred to the internal sense only, while the representations which indicate extended beings are referred to the external sense also. With reference to the reality of external objects, I need as little trust to inference, as with reference to the reality of the object of my internal sense (my thoughts), both being nothing but representations, the immediate perception (consciousness) of which is at the same time a sufficient proof of their reality.

  The transcendental idealist is, therefore, an empirical realist, and allows to matter, as a phenomenon, a reality which need not be inferred, but may be immediately perceived. The transcendental realism, on the contrary, is necessarily left in doubt, and obliged to give way to empirical idealism, because it considers the objects of the external senses as something different from the senses themselves, taking mere phenomena as independent beings, existing outside us. And while with the very best consciousness of our representation of these things, it is far from certain that, if a representation exists, its corresponding object must exist also, it is clear that in our system external things, that is, matter in all its shapes and changes, are nothing but mere phenomena, that is, representations within us, of the reality of which we are immediately conscious.

  As, so far as I know, all psychologists who believe in empirical idealism are transcendental realists, they have acted no doubt quite consistently, in ascribing great importance to empirical idealism, as one of the problems from which human reason could hardly extricate itself. For indeed, if we consider external phenomena as representations produced inside us by their objects, as existing as things by themselves outside us, it is difficult to see how their existence could be known otherwise but through a syllogism from effect to cause, where it must always remain doubtful, whether the cause be within or without us. Now we may well admit that something which, taken transcendentally, is outside us, may be the cause of our external intuitions, but this can never be the object which we mean by the representations of matter and material things; for these are phenomena only, that is, certain kinds of representations existing always within us, and the reality of which depends on our immediate consciousness, quite as much as the consciousness of my own thoughts. The transcendental object is unknown equally in regard to internal and external intuition.

  Of this, however, we are not speaking at present, but only of the empirical object, which is called external, if represented in space, and internal, when represented in temporal relations only, both space and time being to be met with nowhere except in ourselves.

  The expression, outside us, involves however an inevitable ambiguity, because it may signify either, something which, as a thing by itself, exists apart from us, or what belongs to outward appearance only. In order, therefore, to remove all uncertainty from that concept, taken in the latter meaning (which alone affects the psychological question as to the reality of our external intuition) we shall distinguish empirically external objects from those that may be called so in a transcendental sense, by calling the former simply things occurring in space.

  Space and time are no doubt representations a priori, which dwell in us as forms of our sensuous intuition, before any real object has determined our senses by means of sensation, enabling them to represent the object under those sensuous conditions. But this something, material or real, that is to be seen in space, presupposes necessarily perception, and cannot be fancied or produced by means of imagination without that perception, which indicates the reality of something in space. It is sensation, therefore, that indicates reality in space and time, according as it is related to the one or the other mode of sensuous intuition. If sensation is once given (which, if referring to an object in general, and not specialising it, is called perception), many an object may be put together in imagination from the manifold materials of perception, which has no empirical place in space or time, but in imagination only. This admits of no doubt, whether we take the sensations of pain and pleasure, or the external ones of colour, heat, etc.; it is always perception by which the material for thinking of any objects of external intuition must be first supplied. This perception, therefore (to speak at present of external intuitions only), represents something real in space. For, first, perception is the representation of a reality, while space is the representation of a mere possibility of coexistence. Secondly, this reality is represented before the external sense, that is, in space. Thirdly, space itself is nothing but mere representation, so that nothing in it can be taken as real, except what is represented in it;6 or, vice versa, whatever is given in it, that is, whatever is represented in it by perception, is also real in it, because, if it were not real in it, that is, given immediately by empirical intuition, it could not be created by fancy, the real of intuition being unimaginable a priori.

  Thus we see that all external perception proves immediately something real in space, or rather is that real itself. Empirical realism is therefore perfectly true, that is, something real in space always corresponds to our external intuitions. Space itself, it is true, with all its phenomena, as representations, exists within me only, but the real or the material of all objects of intuition is nevertheless given in that space, independent of all fancy or imagination; nay, it is impossible that in that space anything outside us (in a transcendental sense) could be given, because space itself is nothing outside our sensibility. The strictest idealist, therefore, can never require that we should prove that the object without us (in its true meaning) corresponds to our perception. For granted there are such obj
ects, they could never be represented and seen, as outside us, because this presupposes space, and the reality in space, as a mere representation, is nothing but the perception itself. It thus follows, that what is real in external phenomena, is real in perception only, and cannot be given in any other way.

  From such perceptions, whether by mere play of fancy or by experience, knowledge of objects can be produced, and here no doubt deceptive representations may arise, without truly corresponding objects, the deception being due, either to illusions of imagination (in dreams), or to a fault of judgment (the so-called deceptions of the senses). In order to escape from these false appearances, one has to follow the rule that, whatever is connected according to empirical laws with a perception, is real. This kind of illusion, however, and its prevention, concerns idealism as well as dualism, since it affects the form of experience only. In order to refute empirical idealism and its unfounded misgivings as to the objective reality of our external perceptions, it is sufficient to consider 1) that external perception proves immediately a reality in space, which space, though in itself a mere form of representations, possesses nevertheless objective reality with respect to all external phenomena (which themselves are mere representations only); 2) that without perception, even the creations of fancy and dreams would not be possible, so that our external senses, with reference to the data from which experience can spring, must have real objects corresponding to them in space.

  There are two kinds of idealists, the dogmatic, who denies the existence of matter, and the sceptical, who doubts it, because he thinks it impossible to prove it. At present we have nothing to do with the former, who is an idealist, because he imagines he finds contradictions in the possibility of matter in general. This is a difficulty which we shall have to deal with in the following section on dialectical syllogisms, treating of reason in its internal struggle with reference to the concepts of the possibility of all that belongs to the connection of experience. The sceptical idealist, on the contrary, who attacks only the ground of our assertion, and declares our conviction of the existence of matter, which we founded on immediate perception, as insufficient, is in reality a benefactor of human reason, because he obliges us, even in the smallest matter of common experience, to keep our eyes well open, and not to consider as a well-earned possession what may have come to us by mistake only. We now shall learn to understand the great advantage of these idealistic objections. They drive us by main force, unless we mean to contradict ourselves in our most ordinary propositions, to consider all perceptions, whether we call them internal or external, as a consciousness only of what affects our sensibility, and to look on the external objects of them, not as things by themselves, but only as representations of which, as of every other representation, we can become immediately conscious, and which are called external, because they depend on what we call the external sense with its intuition of space, space being itself nothing but an internal kind of representation in which certain perceptions become associated.