Critique of Pure Reason

by Immanuel Kant

  Thirdly. The Leibnizian monadology has really no other foundation than that Leibniz represented the difference of the internal and the external in relation to the understanding only. Substances must have something internal, which is free from all external relations, and therefore from composition also. The simple, therefore, or uncompounded, is the foundation of the internal of things by themselves. This internal in the state of substances cannot consist in space, form, contact, or motion (all these determinations being external relations), and we cannot therefore ascribe to substances any other internal state but that which belongs to our own internal sense, namely, the state of representations. This is the history of the monads, which were to form the elements of the whole universe, and the energy of which consists in representations only, so that properly they can be active within themselves only.

  For this reason, his principle of a possible community of substances could only be a pre-established harmony, and not a physical influence. For, as everything is actively occupied internally only, that is, with its own representations, the state of representations in one substance could not be in active connection with that of another; but it became necessary to admit a third cause, exercising its influence on all substances, and making their states to correspond with each other, not indeed by occasional assistance rendered in each particular case (systema assistentiae), but through the unity of the idea of a cause valid for all, and in which all together must receive their existence and permanence, and therefore also their reciprocal correspondence according to universal laws.

  Fourthly. Leibniz's celebrated doctrine of space and time, in which he intellectualised these forms of sensibility, arose entirely from the same delusion of transcendental reflection. If by means of the pure understanding alone I want to represent the external relations of things, I can do this only by means of the concept of their reciprocal action; and if I want to connect one state with another state of the same thing, this is possible only in the order of cause and effect. Thus it happened that Leibniz conceived space as a certain order in the community of substances, and time as the dynamical sequence of their states. That which space and time seem to possess as proper to themselves and independent of things, he ascribed to the confusion of these concepts. which made us mistake what is a mere form of dynamical relations for a peculiar and independent intuition, antecedent to things themselves. Thus space and time became with him the intelligible form of the connection of things (substances and their states) by themselves, and things were intelligible substances (substantiae noumena). Nevertheless he tried to make these concepts valid for phenomena, because he would not concede to sensibility any independent kind of intuition, but ascribed all, even the empirical representation of objects, to the understanding, leaving to the senses nothing but the contemptible work of confusing and mutilating the representations of the understanding.

  But, even if we could predicate anything synthetically by means of the pure understanding of things by themselves (which however is simply impossible), this could never be referred to phenomena, because these do not represent things by themselves. We should therefore in such a case have to compare our concepts in a transcendental reflection under the conditions of sensibility only, and thus space and time would never be determinations of things by themselves, but of phenomena. What things may be by themselves we know not, nor need we care to know, because, after all, a thing can never come before me otherwise than as a phenomenon.

  The remaining reflective conceptions have to be treated in the same manner. Matter is substantial phenomenon. What may belong to it internally, I seek for in all parts of space occupied by it, and in all effects produced by it, all of which, however, can be phenomena of the external senses only. I have therefore nothing that is absolutely, but only what is relatively internal, and this consists itself of external relations. Nay, what according to the pure understanding should be the absolutely internal of matter is a mere phantom, for matter is never an object of the pure understanding, while the transcendental object which may be the ground of the phenomenon which we call matter, is a mere something of which we could not even understand what it is, though somebody should tell us. We cannot understand anything except what carries with it in intuition something corresponding to our words. If the complaint 'that we do not understand the internal of things,' means that we do not comprehend by means of the pure understanding what the things which appear to us may be of themselves, it seems totally unjust and unreasonable; for it means that without senses we should be able to know and therefore to see things, that is, that we should possess a faculty of knowledge totally different from the human, not only in degree, but in kind and in intuition, in fact, that we should not be men, but beings of whom we ourselves could not say whether they are even possible, much less what they would be like. Observation and analysis of phenomena enter into the internal of nature, and no one can say how far this may go in time. Those transcendental questions, however, which go beyond nature, would nevertheless remain unanswerable, even if the whole of nature were revealed to us, for it is not given to us to observe even our own mind with any intuition but that of our internal sense. In it lies the mystery of the origin of our sensibility. Its relation to an object, and the transcendental ground of that unity, are no doubt far too deeply hidden for us, who can know even ourselves by means of the internal sense only, that is, as phenomena, and we shall never be able to use the same imperfect instrument of investigation in order to find anything but again and again phenomena, the non-sensuous, and non-phenomenal cause of which we are seeking in vain.

  What renders this criticism of the conclusions by means of the acts of mere reflection extremely useful is, that it shows clearly the nullity of all conclusions with regard to objects compared with each other in the understanding only, and that it confirms at the same time what we have so strongly insisted on, namely, that phenomena, though they cannot be comprehended as things by themselves among the objects of the pure understanding, are nevertheless the only objects in which our knowledge can possess objective reality, i.e. where intuition corresponds to concepts.

  When we reflect logically only, we only compare in our understanding concepts among themselves, trying to find out whether both have exactly the same contents, whether they contradict themselves or not, whether something belongs to a concept, or is added to it, and which of the two may be given, while the other may be a mode only of thinking the given concept. But if I refer these concepts to an object in general (in a transcendental sense), without determining whether it be an object of sensuous or intellectual intuition, certain limitations appear at once, warning us not to go beyond the concept, and upsetting all empirical use of it, thus proving that a representation of an object, as of a thing in general, is not only insufficient, but, if without sensuous determination, and independent of empirical conditions, self-contradictory. It is necessary therefore either to take no account at all of the object (as we do in logic) or, if not, then to think it under the conditions of sensuous intuition, because the intelligible would require a quite peculiar intuition which we do not possess, and, without it, would be nothing to us, while on the other side phenomena also could never be things by themselves. For if I represent to myself things in general only, the difference of external relations cannot, it is true, constitute a difference of the things themselves, but rather presupposes it; and, if the concept of one thing does not differ at all internally from that of another, I only have one and the same thing placed in different relations. Furthermore, by adding a mere affirmation (reality) to another, the positive in it is indeed augmented, and nothing is taken away or removed, so that we see that the real in things can never be in contradiction with itself, etc.

  A certain misunderstanding of these reflective concepts has, as we showed, exercised so great an influence on the use of the understanding, as to mislead even one of the most acute philosophers to the adoption of a so-called system of intellectual knowledge, which undertakes to determine objects without the
intervention of the senses. For this reason the exposition of the cause of the misunderstanding, which lies in the amphiboly of these concepts, as the origin of false principles, is of great utility in determining and securing the true limits of the understanding. It is no doubt true, that what can be affirmed or denied of a concept in general, can also be affirmed or denied of any part of it (dictum de omni et nullo); but it would be wrong so to change this logical proposition as to make it say that whatever is not contained in a general concept, is not contained either in the particular concepts comprehended under it; for these are particular concepts for the very reason that they contain more than is conceived in the general concept. Nevertheless the whole intellectual system of Leibniz is built up on this fallacy, and with it falls necessarily to the ground, together with all equivocation in the use of the understanding, that had its origin in it.

  Leibniz's principle of discernibility is really based on the supposition that, if a certain distinction is not to be found in the general concept of a thing, it could not be met with either in the things themselves, and that therefore all things were perfectly the same (numero eadem), which are not distinguished from each other in their concept also, as to quality or quantity. And because in the mere concept of a thing, no account has been taken of many a necessary condition of its intuition, it has rashly been concluded that that which, in forming an abstraction, has been intentionally left out of account, did really not exist anywhere, and nothing has been allowed to a thing except what is contained in its concept.

  The concept of a cubic foot of space, wherever and how many times soever I may think it, is in itself perfectly the same. But two cubic feet are nevertheless distinguished in space, by their places alone (numero diversa), and these places are conditions of the intuition in which the object of our concept is given, and which, though they do not belong to the concept, belong nevertheless to the whole of sensibility. In a similar manner there is no contradiction in the concept of a thing, unless something negative has been connected with something affirmative; and simply affirmative concepts, if joined together, cannot neutralise each other. But in sensuous intuition, where we have to deal with reality (for instance motion), there exist conditions (opposite directions) of which in the concept of motion in general no account was taken, and which render possible an opposition (not however a logical one), and from mere positives produce zero = 0, so that it would be wrong to say that all reality must be in perfect agreement, if there is no opposition between its concepts.2 If we keep to concepts only, that which we call internal is the substratum of all relations or external determinations. If therefore I take no account of any of the conditions of intuition, and confine myself solely to the concept of a thing, then I may drop no doubt all external relations, and yet there must remain the concept of something which implies no relation, but internal determinations only. From this it might seem to follow that there exists in everything something (substance) which is absolutely internal, preceding all external determinations, nay, rendering them possible. It might likewise seem to follow that this substratum, as no longer containing any external relations, must be simple (for corporeal things are always relations only, at least of their parts existing side by side); and as we know of no entirely internal determinations beyond those of our own internal sense, that substratum might be taken, not only as simple, but likewise (according to the analogy of our own internal sense) as determined by representations, so that all things would be really monads, or simple beings endowed with representations. All this would be perfectly true, unless something more than the concept of a thing in general were required in order to give us objects of external intuition, although the pure concept need take no account of it. But we see, on the contrary, that a permanent phenomenon in space (impenetrable extension) may contain mere relations without anything that is absolutely internal, and yet be the first substratum of all external perception. It is true that if we think by concepts only, we cannot think something external without something internal, because conceptions of relations presuppose things given, and are impossible without them. But as in intuition something is contained which does not exist at all in the mere concept of a thing, and as it is this which supplies the substratum that could never be known by mere concepts, namely, a space which, with all that is contained in it, consists of purely formal, or real relations also, I am not allowed to say, that, because nothing can be represented by mere concepts without something absolutely internal, there could not be in the real things themselves; comprehended under those concepts, and in their intuition, anything external, without a foundation of something absolutely internal. For, if we take no account of all conditions of intuition, then no doubt nothing remains in the mere concept but the internal in general, with its mutual relations, through which alone the external is possible. This necessity, however, which depends on abstraction alone, does not apply to things, if they are given in intuition with determinations expressive of mere relations, and without having for their foundation anything internal, for the simple reason that they are phenomena only, and not things in themselves. Whatever we may know of matter are nothing but relations (what we call internal determinations are but relatively internal); but there are among these relations some which are independent and permanent, and by which a certain object is given us. That I, when abstraction is made of these relations, have nothing more to think, does not do away with the concept of a thing, as a phenomenon, nor with the concept of an object in abstracto. It only shows the impossibility of such an object as could be determined by mere concepts, that is of a noumenon. It is no doubt startling to hear, that a thing should consist entirely of relations, but such a thing as we speak of is merely a phenomenon, and can never be thought by means of the categories only; nay, it consists itself of the mere relation of something in general to our senses. In the same manner, it is impossible for us to represent the relations of things in abstracto as long as we deal with concepts only, in any other way than that one should be the cause of determinations in the other, this being the very concept of our understanding, with regard to relations. But as in this case we make abstraction of all intuition, a whole class of determinations, by which the manifold determines its place to each of its component parts, that is, the form of sensibility (space), disappears, though in truth it precedes all empirical casualty.

  If by purely intelligible objects we understand things which, without all schemata of sensibility, are thought by mere categories, such objects are simply impossible. It is our sensuous intuition by which objects are given to us that forms the condition of the objective application of all the concepts of our understanding, and without that intuition the categories have no relation whatever to any object. Nay, even if we admitted a kind of intuition different from the sensuous, our functions of thought would have no meaning with regard to it. If we only mean objects of a non-sensuous intuition, to which our categories do not apply, and of which we can have no knowledge whatever (either intuitional or conceptual), there is no reason why noumena, in this merely negative meaning, should not be admitted, because in this case we mean no more than this, that our intuition does not embrace all things, but objects of our senses only; that, consequently, its objective validity is limited, and space left for some other kind of intuition, and consequently for things as objects of it. But in that sense the concept of a noumenon is problematical, that is, the representation of a thing of which we can neither say that it is possible or that it is impossible, because we have no conception of any kind of intuition but that of our senses, or of any kind of concepts but of our categories, neither of them being applicable to any extra-sensuous object. We cannot therefore extend in a positive sense the field of the objects of our thought beyond the conditions of our sensibility, or admit, besides phenomena, objects of pure thought, that is, noumena, simply because they do not possess any positive meaning that could be pointed out. For it must be admitted that the categories by themselves are not sufficient for a knowledge of things, and that, witho
ut the data of sensibility, they would be nothing but subjective forms of unity of the understanding, and without an object. We do not say that thought is a mere product of the senses, and therefore limited by them, but it does not follow that therefore thought, without sensibility, has its own pure use, because it would really be without an object. Nor would it be right to call the noumenon such an object of the pure understanding, for the noumenon means the problematical concept of an object, intended for an intuition and understanding totally different from our own, and therefore themselves mere problems. The concept of the noumenon is not therefore the concept of an object, but only a problem, inseparable from the limitation of our sensibility, whether there may not be objects independent of its intuition. This is a question that can only be answered in an uncertain way, by saying that as sensuous intuition does not embrace all things without exception, there remains a place for other objects, that cannot therefore be absolutely denied, but cannot be asserted either as objects of our understanding, because there is no definite concept for them (our categories being unfit for that purpose).

  The understanding therefore limits the sensibility without enlarging thereby its own field, and by warning the latter that it can never apply to things by themselves, but to phenomena only, it forms the thought of an object by itself, but as transcendental only, which is the cause of phenomena, and therefore never itself a phenomenon: which cannot be thought as quantity, nor as reality, nor as substance (because these concepts require sensuous forms in which to determine an object), and of which therefore it must always remain unknown, whether it is to be found within us only, or also without us; and whether, if sensibility were removed, it would vanish or remain. If we like to call this object noumenon, because the representation of it is not sensuous, we are at liberty to do so. But as we cannot apply to it any of the concepts of our understanding, such a representation remains to us empty, serving no purpose but that of indicating the limits of our sensuous knowledge, and leaving at the same time an empty space which we cannot fill either by possible experience, or by the pure understanding.