Transcendental Aesthetic

B 31 Critique of Pure Reason

I. Transcendental Doctrine of Elements

B 33 Transcendental Doctrine of Elements First Part Transcendental Aesthetic

§ 1

In whatever manner and by whatever means a cognition may relate to objects, the manner in which it relates to them immediately, and toward which all thinking as a means is directed, is intuition. But intuition occurs only insofar as the object is given to us; and this, in turn, is possible, for us human beings at least, only through its affecting the mind in a certain way. The capacity (receptivity) to receive representations through the way objects affect us is called sensibility. Through sensibility, then, objects are given to us, and it alone supplies us with intuitions; through the understanding, however, they are thought, and from it concepts arise. But all thinking must ultimately relate, whether straightaway (directly) or by a detour (indirectly), through certain marks, to intuitions, and hence, in our case, to sensibility, because no object can be given to us in any other way.

B 34 The effect of an object on the capacity for representation, insofar as we are affected by it, is sensation. An intuition that relates to the object through sensation is called empirical. The undetermined object of an empirical intuition is called appearance.

In appearance I call what corresponds to sensation its matter; but what makes it possible for the manifold of appearance to be ordered in certain relations I call the form of appearance. Since that in which alone sensations can be ordered and placed in a certain form cannot itself in turn be sensation, the matter of all appearance is indeed given to us only a posteriori, but its form must lie ready for all appearances a priori in the mind, and must therefore be capable of being considered apart from all sensation.

I call all representations pure (in the transcendental sense) in which nothing belonging to sensation is encountered. Accordingly, the pure form of sensible intuitions in general, in which all the manifold of appearances is intuited in certain relations, will be found a priori in the mind. This pure form of sensibility will itself also be called pure intuition.

B 35 Thus, if I separate from the representation of a body what the understanding thinks of it—substance, force, divisibility, and so on—and likewise what belongs in it to sensation—impenetrability, hardness, color, and so on—something from this empirical intuition still remains for me: namely, extension and shape. These belong to pure intuition, which occurs a priori in the mind as a mere form of sensibility, even without an actual object of the senses or sensation.

A science of all a priori principles of sensibility I call transcendental aesthetic*.

B 36 There must therefore be such a science, forming the first part of the transcendental doctrine of elements, in contrast to the science that contains the principles of pure thinking and is called transcendental logic.

* The Germans are the only people who now use the word “aesthetic” to designate what others call the critique of taste. Underlying this is a mistaken hope entertained by the excellent analyst Baumgarten: to bring the critical judging of beauty under principles of reason and raise its rules to a science. But this effort is futile. For the rules or criteria in question are, in their principal sources, merely empirical, and can therefore never serve as determinate a priori laws to which our judgment of taste would have to conform. Rather, the latter constitutes the proper touchstone of the correctness of the former. It is therefore advisable either to let this use of the name lapse again and reserve it for the doctrine that is a true science—which would also bring us closer to the language and sense of the ancients, among whom the division of cognition into aistheta kai noeta was very well known—or to share the name with speculative philosophy and take aesthetic partly in a transcendental sense and partly in a psychological meaning.

In transcendental aesthetic, then, we will first isolate sensibility by separating out everything the understanding thinks in connection with it through its concepts, so that nothing but empirical intuition remains. Second, we will detach from this everything belonging to sensation, so that nothing but pure intuition and the mere form of appearances remains, which is the only thing sensibility can supply a priori. In this investigation we will find that there are two pure forms of sensible intuition as principles of a priori cognition, namely space and time, which we will now consider.

B 37 Transcendental Aesthetic First Section On Space

§ 2 Metaphysical exposition of this concept

Through outer sense (a property of our mind) we represent objects as outside us, and all of them in space. In space their shape, magnitude, and relation to one another are determined or determinable. Inner sense, through which the mind intuits itself or its inner state, does not indeed give an intuition of the soul itself as an object; yet there is a determinate form under which alone the intuition of its inner state is possible, so that everything belonging to inner determinations is represented in relations of time. Time cannot be intuited outwardly, any more than space can be intuited as something within us. What, then, are space and time? Are they actual beings? Are they, to be sure, only determinations or relations of things, but such as would belong to things even in themselves, even if they were not intuited?

B 38 Or are they such as attach only to the form of intuition, and hence to the subjective constitution of our mind, without which these predicates cannot be ascribed to any thing at all? To learn about this, let us first expound the concept of space. By exposition (expositio) I understand the clear (though not exhaustive) representation of what belongs to a concept; an exposition is metaphysical when it contains what presents the concept as given a priori.

1 Space is not an empirical concept abstracted from outer experiences. For in order that certain sensations be referred to something outside me, that is, to something in a different place in space from the one in which I am, and likewise in order that I may represent them as outside and alongside one another, hence not merely as different but as in different places, the representation of space must already lie at the foundation. Accordingly, the representation of space cannot be borrowed through experience from the relations of outer appearance; rather, this outer experience is itself first possible only through that representation.

2 Space is a necessary a priori representation that underlies all outer intuitions. We can never form a representation of there being no space, although we can quite well think of no objects being encountered in it.

B 39 Space is therefore regarded as the condition of the possibility of appearances, not as a determination dependent on them, and is an a priori representation that necessarily underlies outer appearances.

3 Space is not a discursive or, as one says, general concept of relations of things in general, but a pure intuition. For, first, we can represent only one single space; and when we speak of many spaces, we mean by this only parts of one and the same unique space. Nor can these parts precede the single all-embracing space as if they were its constituents (from which its composition would be possible); they can be thought only in it. Space is essentially one; the manifold in it, and hence also the general concept of spaces in general, rests solely on limitations. From this it follows that an a priori intuition (which is not empirical) underlies all concepts of space. Thus all geometrical principles too—for example, that in a triangle two sides together are greater than the third—are never derived from general concepts of line and triangle, but from intuition, and indeed a priori with apodictic certainty.

4 Space is represented as an infinite given magnitude.

B 40 Now every concept must indeed be thought as a representation contained in an infinite multitude of different possible representations (as their common mark), and hence as containing these under itself. But no concept as such can be thought as containing an infinite multitude of representations within itself. Yet space is thought in this way (for all the parts of space, to infinity, exist simultaneously). Therefore the original representation of space is a priori intuition, not a concept.

§ 3 Transcendental exposition of the concept of space

By a transcendental exposition I understand the explanation of a concept as a principle from which the possibility of other synthetic a priori cognitions can be understood. For this purpose it is required 1) that such cognitions actually flow from the given concept, and 2) that these cognitions be possible only on the assumption of a given way of explaining this concept.

Geometry is a science that determines the properties of space synthetically and yet a priori. What, then, must the representation of space be for such a cognition of it to be possible?

B 41 It must originally be intuition; for from a mere concept no propositions can be drawn that go beyond the concept, which is nevertheless what happens in geometry (Introduction V). But this intuition must be found in us a priori, that is, before all perception of an object, and must therefore be pure, not empirical intuition. For geometrical propositions are all apodictic, that is, combined with the consciousness of necessity—for example, space has only three dimensions. Such propositions, however, cannot be empirical judgments or judgments of experience, nor can they be inferred from them (Introduction II).

How, then, can an outer intuition reside in the mind that precedes the objects themselves, and in which the concept of these objects can be determined a priori? Plainly in no other way than insofar as it has its seat solely in the subject, as the subject’s formal constitution for being affected by objects and thereby receiving an immediate representation of them, that is, intuition; thus only as the form of outer sense in general.

Our explanation alone, therefore, makes comprehensible the possibility of geometry as a synthetic a priori cognition. Any mode of explanation that does not provide this, even if it appears to bear some resemblance to ours, can most securely be distinguished from it by these marks.

B 42 Conclusions from the above concepts

a) Space represents no property whatever of any things in themselves, nor things in their relation to one another; that is, it represents no determination of them that attaches to the objects themselves and would remain even if we abstracted from all subjective conditions of intuition. For neither absolute nor relative determinations can be intuited before the existence of the things to which they belong, hence not a priori.

b) Space is nothing other than the form of all appearances of outer senses, that is, the subjective condition of sensibility under which alone outer intuition is possible for us. Since the subject’s receptivity for being affected by objects necessarily precedes all intuitions of these objects, we can understand how the form of all appearances can be given in the mind before all actual perceptions, hence a priori; and how, as a pure intuition in which all objects must be determined, it can contain principles of their relations prior to all experience.

Accordingly, we can speak of space, extended beings, and so on only from a human standpoint. If we depart from the subjective condition under which alone we can receive outer intuition, namely as we may be affected by objects, the representation of space means nothing at all.

B 43 This predicate is ascribed to things only insofar as they appear to us, that is, are objects of sensibility. The constant form of this receptivity, which we call sensibility, is a necessary condition of all relations in which objects are intuited as outside us; and, if we abstract from these objects, it is a pure intuition bearing the name of space. Since we cannot make the special conditions of sensibility into conditions of the possibility of things, but only of their appearances, we can indeed say that space comprises all things that may appear to us outwardly, but not all things in themselves, whether they are intuited or not, or by whatever subject they may be intuited. For we cannot judge at all whether the intuitions of other thinking beings are bound to the same conditions that limit our intuition and are universally valid for us. If we add the restriction of a judgment to the concept of its subject, the judgment then holds unconditionally. The proposition “All things are alongside one another in space” holds under the restriction that these things are taken as objects of our sensible intuition. If I add the condition to the concept here and say, “All things, as outer appearances, are alongside one another in space,” this rule holds universally and without restriction.

B 44 Our expositions accordingly teach the reality, that is, the objective validity, of space with regard to everything that can come before us outwardly as an object, but at the same time the ideality of space with regard to things when reason considers them in themselves, that is, without regard to the constitution of our sensibility. We therefore assert the empirical reality of space (with regard to all possible outer experience), while at the same time asserting its transcendental ideality: that it is nothing as soon as we leave aside the condition of the possibility of all experience and take it as something underlying things in themselves.

But apart from space there is also no other subjective representation related to something outer that could be called a priori objective. For from none of them can synthetic a priori propositions be derived, as they can from intuition in space, § 3. Strictly speaking, therefore, no ideality at all belongs to them, although they agree with the representation of space in belonging merely to the subjective constitution of our manner of sensing—for example, of sight, hearing, and touch, through sensations of colors, sounds, and warmth. But because these are mere sensations and not intuitions, they do not in themselves allow us to cognize any object, least of all a priori.

B 45 The intention of this observation is only to prevent anyone from attempting to elucidate the asserted ideality of space through quite inadequate examples: for instance, that colors, taste, and so on are rightly regarded not as constitutions of things but merely as modifications of our subject, which can even differ in different people. For in this case what is originally itself only appearance—for example, a rose—is taken in the empirical sense for a thing in itself, which may nevertheless appear differently in color to every eye. By contrast, the transcendental concept of appearances in space is a critical reminder that nothing intuited in space is a thing in itself, nor is space a form of things that might belong to them in themselves. Rather, objects in themselves are not known to us at all, and what we call outer objects are nothing other than mere representations of our sensibility, whose form is space. Their true correlate, however, that is, the thing in itself, is not cognized through these representations at all, nor can it be; yet it is also never inquired after in experience.

B 46 Transcendental Aesthetic Second Section On Time

§ 4 Metaphysical exposition of the concept of time

Time is 1. not an empirical concept abstracted from any experience. For simultaneity or succession would not itself enter perception if the representation of time did not underlie it a priori. Only on this presupposition can we represent that some things exist at one and the same time (simultaneously) or at different times (successively).

2 Time is a necessary representation that underlies all intuitions. With regard to appearances in general, we cannot remove time itself, although we can quite well take appearances out of time. Time is therefore given a priori. In it alone is all actuality of appearances possible. These can all fall away, but time itself, as the universal condition of their possibility, cannot be removed.

B 47 3. This a priori necessity also grounds the possibility of apodictic principles concerning the relations of time, or axioms of time in general. It has only one dimension: different times are not simultaneous but successive (just as different spaces are not successive but simultaneous). These principles cannot be drawn from experience, for experience would yield neither strict universality nor apodictic certainty. We could say only, “This is what ordinary perception teaches,” but not, “This is how it must be.” These principles hold as rules under which experiences are possible at all, and instruct us before experience, not through it.

4 Time is not a discursive or, as it is called, general concept, but a pure form of sensible intuition. Different times are only parts of the very same time. But a representation that can be given only through a single object is intuition. Nor could the proposition that different times cannot be simultaneous be derived from a general concept. The proposition is synthetic and cannot arise from concepts alone. It is therefore immediately contained in the intuition and representation of time.

5 The infinity of time means nothing more than that every determinate magnitude of time is possible only through limitations of one single time lying at the foundation.

B 48 The original representation, time, must therefore be given as unlimited. But where the parts themselves, and every magnitude of an object, can be represented determinately only through limitation, the whole representation must not be given through concepts (for these contain only partial representations); rather, immediate intuition must underlie them.

§ 5 Transcendental exposition of the concept of time

For this I can refer to No. 3, where for brevity I placed what is properly transcendental among the articles of the metaphysical exposition. Here I add that the concept of alteration and, with it, the concept of motion (as change of place) are possible only through and in the representation of time. If this representation were not an a priori (inner) intuition, no concept, whatever it might be, could make comprehensible the possibility of an alteration, that is, of a combination of contradictorily opposed predicates in one and the same object—for example, the being in a place and the not-being in that same place of the very same thing.

B 49 Only in time can both contradictorily opposed determinations be encountered in one thing, namely successively. Our concept of time thus explains the possibility of as many synthetic a priori cognitions as are set forth by the general theory of motion, which is by no means unfruitful.

§ 6 Conclusions from these concepts

a) Time is not something that would subsist on its own or inhere in things as an objective determination, and would thus remain if we abstracted from all subjective conditions of intuiting them. For in the first case it would be something actual without an actual object. As for the second, as a determination or order inhering in things themselves, it could not precede objects as their condition and be cognized and intuited a priori through synthetic propositions. This latter is, by contrast, quite possible if time is nothing but the subjective condition under which all intuitions can occur in us. For then this form of inner intuition can be represented before the objects, hence a priori.

b) Time is nothing other than the form of inner sense, that is, of the intuition of ourselves and of our inner state. For time can be no determination of outer appearances.

B 50 It belongs neither to a shape nor to a position, and so on, but instead determines the relation of representations in our inner state. And precisely because this inner intuition yields no shape, we also seek to compensate for this lack through analogies, representing the succession of time by a line extending to infinity, in which the manifold constitutes a series of only one dimension. From the properties of this line we infer all the properties of time, except the single one that the parts of the former are simultaneous, whereas those of the latter are always successive. From this it also becomes clear that the representation of time is itself intuition, because all its relations can be expressed in an outer intuition.

c) Time is the a priori formal condition of all appearances in general. Space, as the pure form of all outer intuition, is limited as an a priori condition merely to outer appearances. By contrast, all representations, whether they have outer things as their object or not, nevertheless belong in themselves, as determinations of the mind, to the inner state; and this inner state falls under the formal condition of inner intuition, hence of time. Time is therefore an a priori condition of all appearance in general: the immediate condition of inner appearances (those of our souls), and precisely thereby also the mediate condition of outer appearances.

B 51 If I can say a priori that all outer appearances are in space and determined a priori according to the relations of space, I can say quite generally, from the principle of inner sense, that all appearances in general, that is, all objects of the senses, are in time and necessarily stand in relations of time.

If we abstract from our way of intuiting ourselves inwardly and, through this intuition, also embracing all outer intuitions in our capacity for representation, and thus take objects as they may be in themselves, then time is nothing. It has objective validity only with regard to appearances, because these are already things we take as objects of our senses. But it is no longer objective if we abstract from the sensibility of our intuition, hence from the way of representing peculiar to us, and speak of things in general. Time is therefore solely a subjective condition of our (human) intuition (which is always sensible, that is, insofar as we are affected by objects), and in itself, apart from the subject, nothing. Nevertheless, with regard to all appearances, and hence also all things that can occur to us in experience, it is necessarily objective. We cannot say, “All things are in time.”

B 52 This is because in the concept of things in general we abstract from every way of intuiting them, whereas this is the very condition under which time belongs to the representation of objects. But if the condition is added to the concept, so that we say, “All things, as appearances (objects of sensible intuition), are in time,” the principle has its proper objective correctness and a priori universality.

Our assertions thus teach the empirical reality of time, that is, objective validity with regard to all objects that may ever be given to our senses. And since our intuition is always sensible, no object can ever be given to us in experience that does not fall under the condition of time. By contrast, we deny time any claim to absolute reality: that it would attach to things absolutely as a condition or property, even without regard to the form of our sensible intuition. Such properties as belong to things in themselves can never be given to us through the senses either. In this, then, consists the transcendental ideality of time: if we abstract from the subjective conditions of sensible intuition, it is nothing at all and can be counted neither as subsisting nor as inhering among objects in themselves (apart from their relation to our intuition).

B 53 Yet this ideality, no more than that of space, is to be compared with the subreptions of sensation. For in those cases we still presuppose that the appearance itself, in which these predicates inhere, has objective reality. Here this falls away entirely, except insofar as it is merely empirical, that is, regards the object itself merely as appearance. On this, see the above observation in the first section.

§ 7 Elucidation

Against this theory, which grants time empirical reality but denies it absolute and transcendental reality, I have heard an objection from insightful men with such unanimity that I infer it must naturally occur to every reader unaccustomed to these reflections. It runs as follows: alterations are actual (this is proved by the change of our own representations, even if one wished to deny all outer appearances along with their alterations). Now alterations are possible only in time; consequently, time is something actual. The answer presents no difficulty. I grant the entire argument. Time is certainly something actual, namely the actual form of inner intuition. It therefore has subjective reality with regard to inner experience; that is, I actually have the representation of time and of my determinations in it.

B 54 It is therefore actually to be regarded not as an object but as the way of representing myself as an object. But if I myself, or another being, could intuit me without this condition of sensibility, the very same determinations that we now represent as alterations would yield a cognition in which the representation of time, and hence also of alteration, did not occur at all. Its empirical reality as the condition of all our experiences therefore remains. Only absolute reality cannot be granted to it, according to what has been said above. It is nothing but the form of our inner intuition*. If we remove from it the special condition of our sensibility, the concept of time also vanishes; it attaches not to the objects themselves, but merely to the subject that intuits them.

* I can indeed say, “My representations follow one another,” but this means only that we are conscious of them as in a temporal succession, that is, according to the form of inner sense. Time is not on that account something in itself, nor a determination attaching objectively to things.

The reason this objection is made so unanimously, even by those who nevertheless know of no convincing objection to the doctrine of the ideality of space, is this.

B 55 They did not hope to demonstrate the absolute reality of space apodictically, because idealism stands against them, holding that the actuality of outer objects admits of no rigorous proof. By contrast, the actuality of the object of our inner sense (myself and my state) is immediately clear through consciousness. The former objects could be mere illusion; but the latter, in their opinion, is undeniably something actual. They did not consider, however, that both, without any need to dispute their actuality as representations, nevertheless belong only to appearance, which always has two sides. On the one side, the object is considered in itself, without regard to the way of intuiting it, and for that very reason its constitution always remains problematic. On the other, attention is paid to the form of the intuition of this object, which must be sought not in the object in itself but in the subject to whom it appears, yet nevertheless actually and necessarily belongs to the appearance of this object.

Time and space are thus two sources of cognition from which various synthetic cognitions can be drawn a priori, as pure mathematics in particular provides a brilliant example with regard to cognitions of space and its relations.

B 56 Taken together, they are pure forms of all sensible intuition and thereby make synthetic a priori propositions possible. But these a priori sources of cognition determine their own boundaries by that very fact (that they are merely conditions of sensibility). Namely, they relate only to objects insofar as these are considered as appearances, and do not present things in themselves. Appearances alone are the field of their validity; if we go beyond it, no further objective use of them occurs. This reality of space and time, moreover, leaves the security of cognition through experience untouched. For we are equally certain of it whether these forms necessarily attach to things in themselves or only to our intuition of these things. By contrast, those who assert the absolute reality of space and time, whether they take them as subsisting or merely inhering, must come into conflict with the principles of experience itself. For if they choose the first alternative (which is generally the position of mathematical investigators of nature), they must assume two eternal and infinite self-subsisting nonentities (space and time) that exist (without there being anything actual) merely to embrace everything actual within themselves. If they choose the second position (held by some metaphysical teachers of nature), space and time count for them as relations of appearances (alongside or successively).

B 57 These relations are abstracted from experience, though represented confusedly in their abstraction. They must then deny a priori mathematical teachings their validity concerning actual things (for example in space), or at least deny their apodictic certainty, since such certainty does not occur a posteriori at all; and on this view the a priori concepts of space and time are only creatures of imagination, whose source must really be sought in experience. From experience’s abstracted relations, imagination has made something that indeed contains their general character, but cannot occur without the restrictions nature has connected with them. The first group gains this much: they clear the field of appearances for mathematical assertions. On the other hand, these very conditions greatly entangle them when the understanding wishes to go beyond this field. The second group does indeed gain in this latter respect: the representations of space and time do not stand in their way when they wish to judge objects not as appearances but merely in relation to the understanding. Yet they can neither account for the possibility of a priori mathematical cognitions, since they lack a true and objectively valid a priori intuition, nor bring the propositions of experience into necessary agreement with those assertions.

B 58 Our theory of the true constitution of these two original forms of sensibility remedies both difficulties.

Finally, it is clear that transcendental aesthetic can contain no more than these two elements, space and time, because all other concepts belonging to sensibility, even that of motion, which unites both elements, presuppose something empirical. For motion presupposes the perception of something movable. In space considered in itself, however, there is nothing movable; hence the movable must be something found in space only through experience, and thus an empirical datum. Likewise, transcendental aesthetic cannot count the concept of alteration among its a priori data. For time itself does not alter, but something in time does. For this, then, perception of some existence and of the succession of its determinations is required, hence experience.

B 59 § 8 General observations on the Transcendental Aesthetic

I. First it will be necessary to explain as clearly as possible what our view is concerning the fundamental constitution of sensible cognition in general, to prevent every misinterpretation of it.

What we have meant to say, then, is that all our intuition is nothing but the representation of appearance; that the things we intuit are not in themselves what we intuit them as being, nor are their relations constituted in themselves as they appear to us; and that if we remove our subject, or even merely the subjective constitution of the senses in general, all the constitution and all the relations of objects in space and time, indeed space and time themselves, would vanish. As appearances they cannot exist in themselves, but only in us. What the objects may be in themselves, apart from all this receptivity of our sensibility, remains entirely unknown to us. We know nothing but our way of perceiving them, which is peculiar to us and need not necessarily belong to every being, though it belongs to every human being. This alone concerns us.

B 60 Space and time are its pure forms; sensation in general is its matter. The former alone we can cognize a priori, that is, before all actual perception, and it is therefore called pure intuition. The latter, however, is that in our cognition which makes it be called a posteriori cognition, that is, empirical intuition. The former attach to our sensibility with absolute necessity, whatever kind our sensations may be; the latter can be very diverse. Even if we could bring this intuition of ours to the highest degree of distinctness, we would thereby come no closer to the constitution of objects in themselves. For we would in any case completely cognize only our way of intuiting, that is, our sensibility, and this always only under the conditions of space and time originally attaching to the subject. What the objects may be in themselves would never become known to us even through the most enlightened cognition of their appearance, which alone is given to us.

To say, therefore, that our entire sensibility is nothing but the confused representation of things, containing solely what belongs to them in themselves but under an accumulation of marks and partial representations that we do not consciously separate, is to falsify the concepts of sensibility and appearance, rendering their entire doctrine useless and empty.

B 61 The distinction between an indistinct and a distinct representation is merely logical and does not concern the content. Without doubt, the concept of right employed by sound understanding contains precisely what the subtlest speculation can develop from it; only in ordinary practical use we are not conscious of these manifold representations in this thought. We cannot therefore say that the ordinary concept is sensible and contains a mere appearance, for right cannot appear at all; rather, its concept lies in the understanding and represents a constitution (the moral one) of actions that belongs to them in themselves. By contrast, the representation of a body in intuition contains nothing at all that could belong to an object in itself, but merely the appearance of something and the way we are affected by it. This receptivity of our capacity for cognition is called sensibility, and remains worlds apart from cognition of the object in itself, even if we were to see through the appearance to its very ground.

The Leibniz-Wolfian philosophy has therefore assigned an entirely mistaken standpoint to all investigations into the nature and origin of our cognitions, in regarding the distinction between sensibility and the intellectual as merely logical.

B 62 It is plainly transcendental, concerning not merely the form of distinctness or indistinctness but the origin and content of these cognitions. Through sensibility we cognize the constitution of things in themselves not merely indistinctly, but not at all; and as soon as we remove our subjective constitution, the represented object, with the properties sensible intuition ascribed to it, is nowhere to be found, nor can it be found. For precisely this subjective constitution determines its form as appearance.

Ordinarily, among appearances, we do distinguish what attaches essentially to their intuition and holds for every human sense in general from what belongs to it only contingently, being valid not in relation to sensibility in general but only to a particular position or organization of this or that sense. We then call the former a cognition that represents the object in itself, and the latter merely its appearance. But this distinction is only empirical. If we stop at it, as usually happens, and do not in turn regard that empirical intuition as mere appearance, as we should, in which nothing at all concerning any thing in itself is to be encountered, then our transcendental distinction is lost. We then believe that we do cognize things in themselves, although everywhere (in the sensible world), even in the deepest investigation of its objects, we deal with nothing but appearances.

B 63 Thus we will indeed call the rainbow a mere appearance during a sun shower, but the rain the thing in itself. This is correct insofar as we understand the latter concept only physically, as that which in universal experience, under every different position relative to the senses, is nevertheless determined in intuition in this and no other way. But if we take this empirical element in general and ask, without attending to its agreement with every human sense, whether it too represents an object in itself (not the raindrops, since these, as appearances, are already empirical objects), then the question of the relation of representation to object is transcendental. Not only are these drops mere appearances, but even their round shape, indeed even the space in which they fall, are nothing in themselves, but mere modifications or foundations of our sensible intuition; the transcendental object, however, remains unknown to us.

The second important concern of our transcendental aesthetic is that it should not merely win some favor as a plausible hypothesis, but be as certain and indubitable as can ever be required of a theory intended to serve as an organon. To make this certainty fully evident, let us choose a case.

B 64 In this case its validity can become manifest, and it can serve to clarify further what was stated in § 3.

Suppose, then, that space and time are objective in themselves and conditions of the possibility of things in themselves. First, it becomes apparent that a great many apodictic and synthetic a priori propositions occur concerning both, especially concerning space, which we therefore wish to investigate here in particular as our example. Since the propositions of geometry are cognized synthetically a priori and with apodictic certainty, I ask: from where do you obtain such propositions, and on what does our understanding rely in order to arrive at such absolutely necessary and universally valid truths? There is no other path than through concepts or through intuitions, both as given either a priori or a posteriori. The latter, namely empirical concepts, and likewise that on which they are grounded, empirical intuition, can yield no synthetic proposition except one that is itself merely empirical, that is, a proposition of experience. Hence it can never contain necessity and absolute universality, which are nevertheless characteristic of all propositions of geometry. As for the first and only means of attaining such cognitions, namely through mere concepts or through a priori intuitions, it is clear that no synthetic cognition at all can be attained from mere concepts, but only analytic cognition.

B 65 Take just the proposition that no space can be enclosed by two straight lines, and hence no figure is possible, and try to derive it from the concept of straight lines and the number two; or take the proposition that a figure is possible from three straight lines, and try likewise to derive it merely from these concepts. All your effort is futile, and you find yourselves compelled to take refuge in intuition, as geometry always does. You therefore give yourselves an object in intuition. But of what kind is this intuition? Is it a pure a priori intuition or an empirical one? If it were the latter, no universally valid proposition, still less an apodictic one, could ever arise from it, for experience can never supply such a thing. You must therefore give your object a priori in intuition and ground your synthetic proposition on it. Now if there did not lie within you a faculty of intuiting a priori; if this subjective condition, as to its form, were not at the same time the universal a priori condition under which alone the object of this (outer) intuition is itself possible; if the object (the triangle) were something in itself without relation to your subject—how could you say that what necessarily lies in your subjective conditions for constructing a triangle must also necessarily belong to the triangle in itself? For you could not add to your concepts (of three lines) something new (the figure).

B 66 That figure would for that reason necessarily have to be encountered in the object, since the object is given before your cognition and not through it. Thus, if space (and likewise time) were not a mere form of your intuition containing a priori conditions under which alone things can be outer objects for you, and without which subjective conditions they are nothing in themselves, you could establish absolutely nothing synthetically a priori about outer objects. It is therefore indubitably certain, and not merely possible or even probable, that space and time, as the necessary conditions of all (outer and inner) experience, are merely subjective conditions of all our intuition. In relation to them, therefore, all objects are mere appearances and not things given for themselves in this manner. For this very reason much can be said a priori about these appearances as regards their form, but never the least thing about the thing in itself that may underlie them.

II. To confirm this theory of the ideality of outer as well as inner sense, and hence of all objects of the senses as mere appearances, the following observation is especially useful: everything in our cognition that belongs to intuition—excluding, therefore, the feeling of pleasure and displeasure, and the will, which are not cognitions at all—contains nothing but mere relations.

B 67 These are relations of places in an intuition (extension), of change of places (motion), and of laws according to which this change is determined (moving forces). But what is present in the place, or what acts in the things themselves apart from the change of place, is not given through this. Now a thing in itself is not cognized through mere relations. We may therefore conclude that, since nothing but mere representations of relations is given to us through outer sense, it too can contain only the relation of an object to the subject in its representation, and not the inner character that belongs to the object in itself. It is just the same with inner intuition. Not only do the representations of outer senses constitute the actual material with which we occupy our mind, but time, in which we place these representations, already contains relations of succession, of simultaneity, and of what is simultaneous with succession (the persistent). Time itself precedes consciousness of these representations in experience and underlies the way we place them in the mind as its formal condition. Now what can precede, as a representation, every act of thinking anything is intuition; and if it contains nothing but relations, it is the form of intuition. Since this form represents nothing except insofar as something is posited in the mind, it can be nothing other than the way the mind is affected through its own activity.

B 68 The activity in question is this positing of its representation, so that the mind is affected through itself, that is, an inner sense as regards its form. Everything represented through a sense is to that extent always appearance. Either, then, no inner sense at all would have to be admitted, or the subject that is its object could be represented through it only as appearance, not as it would judge itself if its intuition were mere self-activity, that is, intellectual. The entire difficulty here rests only on how a subject can intuit itself inwardly; but this difficulty is common to every theory. Consciousness of oneself (apperception) is the simple representation of the I; and if through this alone all the manifold in the subject were given by its own activity, inner intuition would be intellectual. In human beings this consciousness requires inner perception of the manifold previously given in the subject, and because of this distinction, the way this manifold is given in the mind without spontaneity must be called sensibility. If the faculty of becoming conscious is to seek out (apprehend) what lies in the mind, it must affect the mind, and only in this way can it produce an intuition of itself. The form of this intuition, however, lies beforehand at the foundation in the mind. It determines, in the representation of time, the way the manifold is together in the mind.

B 69 The mind thus intuits itself not as it would immediately represent itself through its own activity, but according to the way it is affected from within, consequently as it appears to itself, not as it is.

III. When I say that in space and time both the intuition of outer objects and the mind’s self-intuition represent each as it affects our senses, that is, as it appears, I do not mean that these objects are mere illusion. For in appearance the objects, indeed even the constitutions we ascribe to them, are always regarded as something actually given. It is only that, insofar as this constitution depends merely on the subject’s way of intuiting in the relation of the given object to it, this object as appearance is distinguished from itself as object in itself. Thus I do not say that bodies merely seem to be outside me, or that my soul only seems to be given in my self-consciousness, when I assert that the quality of space and time, in conformity with which I posit both as the condition of their existence, lies in my way of intuiting and not in these objects in themselves. It would be my own fault if I made mere illusion out of what I ought to count as appearance*. But this does not happen according to our principle of the ideality of all our sensible intuitions.

B 70 Rather, if objective reality is ascribed to those forms of representation, it is impossible to avoid transforming everything through them into mere illusion. For if space and time are regarded as constitutions that must be encountered, as to their possibility, in things in themselves, and we reflect on the absurdities in which we then entangle ourselves, namely two infinite things that are neither substances nor anything actually inhering in substances.

B 71 These things must nevertheless exist, indeed must be the necessary condition of the existence of all things, and must remain even if all existing things are removed. Then we can hardly blame the good Berkeley for reducing bodies to mere illusion. Indeed, even our own existence, which would in this way be made dependent on the independently subsisting reality of a nonentity such as time, would have to be transformed along with it into sheer illusion, an absurdity of which no one has yet been guilty.

* The predicates of appearance can be ascribed to the object itself in relation to our sense: for example, the red color or the scent to the rose. But illusion can never be ascribed to the object as a predicate, precisely because it ascribes to the object in itself what belongs to it only in relation to the senses, or to the subject in general: for example, the two handles initially ascribed to Saturn. What is not to be encountered in the object in itself at all, but is always to be encountered in its relation to the subject and is inseparable from the representation of the former, is appearance. Thus the predicates of space and time are rightly ascribed to objects of the senses as such, and there is no illusion in this. But if I ascribe redness to the rose in itself, handles to Saturn, or extension in itself to all outer objects, without regard to a determinate relation of these objects to the subject and without restricting my judgment to it, only then does illusion arise.

IV. In natural theology, where one thinks an object that not only cannot be an object of intuition for us at all, but cannot in any way be an object of sensible intuition even to itself, one is careful to remove the conditions of time and space from all its intuition. For all its cognition must be intuition, not thinking, which always indicates limits. But by what right can one do this if one has previously made both into forms of things in themselves, indeed forms that, as a priori conditions of the existence of things, remain even if the things themselves have been removed? For as conditions of all existence in general, they would also have to be conditions of God’s existence. If we do not wish to make them objective forms of all things, nothing else remains.

B 72 We must make them subjective forms of our way of intuiting, outer as well as inner. This is called sensible because it is not original, that is, not such that through it the very existence of the object of intuition is given (which, so far as we can see, can belong only to the primordial being), but is dependent on the existence of the object, and is thus possible only through the object’s affecting the subject’s capacity for representation.

Nor is it necessary for us to restrict the way of intuiting in space and time to human sensibility. It may be that all finite thinking beings must necessarily agree with human beings in this, although we cannot decide it. Yet this universal validity does not make it cease to be sensibility, precisely because it is derivative (intuitus derivativus), not original (intuitus originarius), and hence not intellectual intuition. For the reason just given, intellectual intuition seems to belong only to the primordial being, never to a being dependent both in its existence and in its intuition, which determines its existence in relation to given objects. This last observation, however, must be counted only as an elucidation of our aesthetic theory, not as a ground of proof.

B 73 Conclusion of the Transcendental Aesthetic

Here, then, we have one of the elements required for solving the general problem of transcendental philosophy: How are synthetic a priori propositions possible? Namely, pure a priori intuitions, space and time. If we wish, in an a priori judgment, to go beyond the given concept, we find in them what can be discovered a priori not in the concept but in the intuition corresponding to it, and can be synthetically combined with that concept. For this reason, however, such judgments never extend further than to objects of the senses, and can hold only for objects of possible experience.

B 31 Critique of Pure Reason

I. Transcendental Doctrine of Elements

B 33 Of the Transcendental Doctrine of Elements First Part The Transcendental Aesthetic

§ 1

Whatever way a cognition relates to objects, and whatever means it uses, intuition is the way it connects to them directly. All thinking works toward intuition as its means. But intuition happens only when the object is given to us. And that, for us humans at least, can happen only if the object affects the mind in some way. We call the capacity (receptivity) to get representations through the way objects affect us sensibility. Objects are therefore given to us through sensibility, and only sensibility gives us intuitions. The understanding, by contrast, thinks objects, and concepts come from it. Still, all thinking has to refer back to intuitions in the end, whether straight on (directly) or by a roundabout way (indirectly), and it does so by means of certain marks. For us that means going back to sensibility, since an object can be given to us by no other route.

B 34 The effect an object has on our capacity for representation, when it affects us, is sensation. Intuition that refers to its object through sensation is called empirical. What we call an appearance is the undetermined object of an empirical intuition.

In an appearance, I call the part that corresponds to sensation its matter. I call the part that makes it possible for the manifold of the appearance to be ordered in certain relations the form of the appearance. The thing in which sensations alone can be ordered and put into a certain form cannot itself be sensation again. So the matter of every appearance is given to us only a posteriori. Its form, however, must lie ready for all appearances together in the mind a priori, and so it can be considered apart from all sensation.

I call a representation pure (in the transcendental sense) when it has nothing in it that belongs to sensation. It follows that a priori, in the mind, we meet the pure form of sensible intuition in general. In that form the whole manifold of appearances gets intuited in certain relations. This pure form of sensibility we will also call pure intuition.

B 35 Suppose I take the representation of a body and separate out what the understanding thinks in it, such as substance, force and divisibility. Suppose I also separate out what belongs to sensation, such as impenetrability, hardness and color. Something is still left over from this empirical intuition, namely extension and shape. These belong to pure intuition, which exists in the mind a priori as a bare form of sensibility, whether or not any real object of sense or sensation is there.

What I call transcendental aesthetic* is the science of all the a priori principles of sensibility. There has to be such a science.

B 36 It is Part One of the transcendental doctrine of elements. Its counterpart is the science that holds the principles of pure thinking, which is named transcendental logic.

* Only the Germans use the word “aesthetic” these days for what other peoples call the critique of taste. The word rests on a hope that failed. The excellent analyst Baumgarten hoped to bring the critical assessment of the beautiful under rational principles and to lift its rules to the level of a science. But this effort is in vain. Such rules, or criteria, are merely empirical in their main sources. They can therefore never serve as definite a priori laws that our judgment of taste would have to follow. It is rather the judgment of taste that is the real touchstone for whether the rules are correct. For this reason it is advisable to let the term lapse again and keep it for the doctrine that is true science. That would also move us nearer to the speech and thinking of the ancients. For them, dividing cognition into aistheta kai noeta (what can be sensed and what can be thought) was very well known. The other option is to share the term with speculative philosophy, and to take “aesthetic” partly in the transcendental sense, partly in the psychological sense.

So in the transcendental aesthetic we begin by isolating sensibility. To do that, we set aside everything the understanding thinks about it with its concepts, so that only empirical intuition remains. Next we split off from that intuition everything that belongs to sensation, leaving only pure intuition and the bare form of appearances. Sensibility can supply nothing else a priori. As we go, we will find that sensible intuition has two pure forms, serving as principles of a priori cognition: space and time. We turn to examine them now.

B 37 Of the Transcendental Aesthetic First Section On Space

§ 2 Metaphysical exposition of this concept

Outer sense is a property of our mind. By means of it we picture objects as lying outside us, every one of them in space. Space is where their shape, size and relation to one another are fixed, or can be fixed. Inner sense is how the mind looks at itself, or at its inner state. It does not, to be sure, hand us any intuition of the soul itself taken as an object. But there is a definite form under which alone we can intuit our inner state. That is why everything among our inner determinations is represented as standing in temporal relations. Neither can time be intuited as something outer, just as space cannot be intuited as something in us. So what are space and time? Are they real beings? Or are they merely determinations, or also relations, of things, but of a kind that would belong to them even in themselves, whether anyone intuited them or not? Or do they cling only to the form of intuition?

B 38 And so to the subjective makeup of our mind alone? Without that makeup, these predicates could not be given to any thing at all. To find out, we first lay out the concept of space. Under the heading of exposition (expositio) I understand a representation that is distinct, though not exhaustive, of whatever belongs to a concept. An exposition is called metaphysical when it covers whatever shows the concept to be given a priori.

1 Space is not an empirical concept drawn from outer experiences. Two things have to be possible. One is that I can refer certain sensations to something outside me. By that I mean something at another spot in space than the spot where I am. The other is that I can represent sensations as outside one another and side by side, so as not just different but in different places. For both, the representation of space must already be the foundation. That means experience cannot have lent us the representation of space from the relations among outer appearances. It is the other way around: this outer experience itself becomes possible only through that representation.

2 Space is a necessary representation, given a priori, which underlies every outer intuition. We can never picture there being no space, though we can easily think of it as containing no objects at all.

B 39 For that reason space counts as the condition that makes appearances possible, not as a determination that depends on them. It is an a priori representation, and it necessarily underlies outer appearances.

3 Space is not a discursive concept, or what people call a general concept of the relations of things as such. It is a pure intuition. To begin with, we can only imagine a single space. If we talk of many spaces, we really mean parts of one and the same space. Nor can these parts precede the one all-embracing space as its building blocks, as if its composition were made possible by them. They can only be thought within it. Space is essentially one. What is manifold in it, and with that the general concept of spaces as such, depends solely on limitations. The consequence is that every concept of space rests on an intuition of it that is a priori and not empirical. That also explains why geometrical principles never come from general concepts of line and triangle. Take the principle that two sides of a triangle together are greater than the third. Such principles are derived from intuition, and a priori, with apodictic certainty.

4 Space is represented as a given magnitude that is infinite.

B 40 Every concept has to be thought of as a representation contained in infinitely many different possible representations, as the mark they share. A concept therefore holds those representations under it. Yet no concept as a concept can be pictured as having infinitely many representations within it. Space is thought of that way, though, since all the parts of space, going on without end, exist at once. So the original representation of space is an a priori intuition and not a concept.

§ 3 Transcendental exposition of the concept of space

By a transcendental exposition I mean the explanation of a concept as a principle from which the possibility of other synthetic a priori cognitions can be understood. This requires two things: 1) that such cognitions actually follow from the given concept, and 2) that they are possible only if this concept is explained in a certain given way.

The science of geometry determines the properties of space, and does so synthetically yet a priori. So what must the representation of space be, for cognition of that kind to be possible at all? It has to be an intuition from the start.

B 41 That’s because no propositions going beyond a concept can be drawn from a mere concept, yet geometry draws them (Introduction V). That intuition must also be found in us a priori, before any perception of an object. So it is pure intuition and not empirical. After all, every geometrical proposition is apodictic, meaning it is joined with a consciousness of its necessity. Space has only three dimensions, for example. Such propositions can’t be empirical, or judgments of experience, and can’t be concluded from them (Introduction II).

Now, how can an outer intuition exist in the mind before the objects themselves, and in such a way that the concept of those objects can be fixed a priori? Plainly it can only be if the intuition has its seat in the subject alone. It would be the subject’s formal makeup for being affected by objects and so getting an immediate representation of them, that is, an intuition. So it can only be the form of outer sense in general.

Only our explanation lets us understand how geometry can be a synthetic a priori cognition. Any way of explaining things that does not deliver this can be told apart from ours most reliably by this sign, even if it seems at first glance to resemble ours somewhat.

B 42 Conclusions from the concepts above

a) Space does not represent any property of things in themselves, nor of those things in their relation to one another. In other words, it shows no determination that clings to the objects themselves and would stay once we leave out every subjective condition of intuition. Absolute determinations and relative ones alike cannot be intuited before the things they belong to exist. So they can’t be intuited a priori either.

b) Space is simply the form of all appearances to the outer senses, in other words the subjective condition of sensibility under which outer intuition is possible for us at all. The subject’s receptivity to being affected by objects necessarily comes before every intuition of those objects. That is how we can grasp that the form of every appearance is given in the mind before any real perception, which is to say a priori. And we can grasp how the same form, being a pure intuition in which every object has to be determined, can contain principles for the relations of those objects before any experience at all.

So we can speak of space, of extended beings and so on, only from the human standpoint. Say we drop the subjective condition under which alone we get outer intuition, namely the way objects may affect us. The representation of space then signifies nothing whatsoever.

B 43 Things get this predicate only to the degree that they appear to us, meaning that they are objects of sensibility. Sensibility is the name for this receptivity, and its form is permanent. It is the necessary condition of every relation within which objects get intuited as external to us. Leave those objects out of account, and what remains is a pure intuition that goes by the name of space. We can only turn the particular conditions of sensibility into conditions for the possibility of appearances, not of things. So we can fairly say that space takes in everything that may appear to us outwardly. It does not take in all things in themselves, whether or not they are intuited, and whoever the subject may be. We cannot tell, for other thinking beings, whether their intuition is bound by the very conditions that limit ours and hold universally for us. Suppose we attach a judgment’s restriction to the concept of the subject. Then the judgment holds without condition. The proposition “All things are side by side in space” is valid with a restriction, the restriction being that we regard the things as objects of our sensible intuition. Suppose I add that condition to the concept and say “As outer appearances, all things are side by side in space.” Then the rule holds universally and with no restriction.

B 44 Our expositions thus teach us the reality (the objective validity) of space for everything that can meet us outwardly as an object. They teach the ideality of space as well, with regard to things that reason weighs as they are in themselves, with no account taken of the nature of our sensibility. We therefore claim the empirical reality of space (for all possible outer experience), and in the same breath its transcendental ideality. That is, space is nothing at all as soon as we set aside what makes all experience possible, and treat space as something that lies at the base of things in themselves.

Apart from space, no other subjective representation that relates to something outer deserves to be called objective a priori. For none of the others lets us derive synthetic propositions a priori, as the intuition in space does (§ 3). So, strictly speaking, they have no ideality at all. They do resemble the representation of space in one respect: they belong only to the subjective makeup of a kind of sense, such as sight, hearing or touch, through sensations of colors, tones and warmth. But these are mere sensations, not intuitions. By themselves they let us cognize no object, least of all a priori.

B 45 This remark has just one aim: to stop anyone from trying to illustrate the claimed ideality of space with examples that fall far short. Colors, taste and the like, for instance, are rightly regarded not as qualities of things but only as changes in our subject, and these can even vary from one person to the next. In that case what is originally only an appearance, a rose for example, counts in the empirical sense as a thing in itself, though it can look different in color to each eye. By contrast, the concept of appearances in space, taken transcendentally, serves as a critical reminder. Whatever we intuit in space is not a thing in itself. Nor is space a form that would belong to things in their own right. Objects in themselves are simply unknown to us. What we call outer objects are only representations of our sensibility, and space is the form of that sensibility. Through them we do not cognize their true correlate, the thing in itself, and we cannot. And experience never asks about it.

B 46 Of the Transcendental Aesthetic Second Section On Time

§ 4 Metaphysical exposition of the concept of time

First (1.), time is not an empirical concept drawn from any experience. Without the representation of time underlying it a priori, we could not perceive simultaneity or succession at all. Time has to be presupposed before one can picture some things as simultaneous (in one and the same time), or as successive (in different times).

2 Time is a necessary representation underlying all intuitions. As far as appearances go, we can’t remove time itself, though we can easily remove the appearances from time. So time is given a priori. All actuality of appearances is possible only in it. The appearances may all vanish, but time itself, as the general condition of their possibility, can’t be abolished.

B 47 3. On this a priori necessity rests, too, the possibility of apodictic principles concerning time-relations, or of axioms about time generally. Time has only one dimension. Different times are not together but one after another, just as different spaces are not one after another but together. Experience cannot be the source of these principles, since it would give neither strict universality nor apodictic certainty. We could report that common perception shows things this way, but never that they have to be this way. These principles hold as the rules under which any experience is possible, and they instruct us ahead of experience, not by means of it.

4 Time is no discursive concept, nor what people call a general concept. It is a pure form of sensible intuition. Different times are merely parts of the very same time. A representation that only a single object can give is an intuition. Besides, no general concept could yield the proposition that different times can’t exist together. That proposition is synthetic, and concepts alone cannot produce it. So it is contained directly in the intuition and representation of time.

5 To say that time is infinite means only that any determinate length of time is possible by limiting one underlying time.

B 48 So the original representation, time, has to be given as unlimited. Whenever the parts themselves, and every magnitude of an object, can be represented as determinate only through limitation, the whole representation cannot be given by concepts, because concepts hold only partial representations. Immediate intuition must lie at its base.

§ 5 Transcendental exposition of the concept of time

So I can point to number 3, where, to keep it short, I put what is properly transcendental under the entries of the metaphysical exposition. Here I add the following. The concept of change is possible only through and within the representation of time. So is the concept of motion, which is change of place. Suppose this representation were not an (inner) intuition a priori. No concept of any kind could then explain to us how a change is possible. A change is a combination of predicates that contradict each other, in one and the same object. Take a thing’s being at a place and the very same thing’s not being at that place.

B 49 Only in time can a single thing be found with both of those contradictory determinations, namely one after the other. So our concept of time explains how there can be as much synthetic a priori cognition as the general doctrine of motion lays out, a doctrine that is far from barren.

§ 6 Conclusions from these concepts

a) Time is not something that would exist by itself, nor something attached to things as an objective determination, which would then remain if one abstracted from all the subjective conditions of intuiting them. If it were the first, time would be real without anything real to go with it. If it were the second, time would be a determination or an order inhering in the things themselves. As such it could not come ahead of the objects as their condition. Nor could synthetic propositions make it known and intuited a priori. Being known and intuited a priori in that way does work, by contrast, if time is merely the subjective condition under which any intuition can occur in us. In that case we can represent this form of inner intuition ahead of the objects, hence a priori.

b) Time is only the form of inner sense, meaning the way we look at ourselves and at our inner state. It cannot be a determination of outer appearances.

B 50 It has nothing to do with shape or position and the like. What it determines is the relation among representations in our inner state. And because this inner intuition gives us no shape, we try to make up the lack through analogies. We represent the sequence of time as a line extending to infinity. The manifold in it forms a series with only one dimension. Every property of time but one we read off from the properties of this line: the parts of the line exist together, but the parts of time are always one after another. This also makes plain that the representation of time is itself an intuition: all its relations can be put into an outer intuition.

c) Time is the formal a priori condition of all appearances in general. Space is the pure form of all outer intuition, and as an a priori condition it reaches no further than outer appearances. Time has no such restriction. Every representation, whether it has outer things as its object or not, belongs in itself, as a determination of the mind, to the inner state. This inner state stands under the formal condition of inner intuition and therefore under time. Time is thus an a priori condition of every appearance. It is the direct condition of inner appearances (those of our souls) and, by that very fact, the indirect condition of outer ones too.

B 51 I can say a priori that every outer appearance is in space and is fixed a priori according to spatial relations. In just the same way, the principle of inner sense lets me say quite generally: every appearance there is, that is, every object of the senses, is in time and necessarily stands in time-relations.

Suppose we leave aside our way of intuiting ourselves inwardly, the way through which all outer intuitions get taken up into our power of representation. Suppose we then consider objects as they might be in themselves. In that case time is nothing. It is objectively valid only for appearances, because those are already things we accept as objects of our senses. Leave out the sensibility of our intuition, our own peculiar way of representing, and speak of things in general: then time is no longer objective. Time is therefore nothing more than a subjective condition for our (human) intuition. Our intuition is always sensible, meaning it depends on objects affecting us. In itself, outside the subject, time is nothing. Even so, it is necessarily objective for all appearances, and so for all things that can meet us in experience. We cannot say that all things are in time.

B 52 The reason is that the concept of things in general leaves out every kind of intuition of them, and that intuition is the real condition under which time enters the representation of objects. Now join the condition to the concept. The principle then reads: when things count as appearances, as objects of sensible intuition, they are all in time. In that form it has sound objective correctness and a priori universality.

Our claims thus teach the empirical reality of time, in other words its objective validity for any object that can ever be presented to our senses. Our intuition is always sensible. So in experience we can never be given an object that escapes the condition of time. What we deny to time is any claim to absolute reality, that is, the idea that time would belong to things simply as a condition or property, even apart from the form of our sensible intuition. The senses could never hand us properties of that sort, the kind that belong to things in themselves. This is what the transcendental ideality of time consists in. According to it, time is simply nothing when the subjective conditions of sensible intuition are set aside. Take objects as they are in themselves, with no regard to how they relate to our intuition. Time can’t be counted among them, whether as subsisting or as inhering.

B 53 Still, this ideality, just like that of space, must not be set beside the subreptions of sensation. In those cases one assumes that the appearance itself, the thing these predicates inhere in, has objective reality. Here that reality disappears altogether, except so far as it is merely empirical, that is, where the object itself is regarded purely as an appearance. For this, see the remark above in the first section.

§ 7 Clarification

The theory allows time to be empirically real while contesting that it is absolutely or transcendentally real. I have heard one objection to it from insightful men, so unanimously that I conclude every reader unused to these thoughts must naturally come up with it. It runs as follows. Changes are real. (Our own representations keep alternating, and that proves it, even if someone wished to deny every outer appearance and its changes.) Now changes are possible only in time. So time is something real. The reply is not hard. I accept the whole argument. Time is indeed something real, namely the real form of inner intuition. It therefore has subjective reality in respect of inner experience. In other words, I truly have the representation of time.

B 54 I also have a representation of my determinations in it. So time is not, in fact, an object. It is the way in which I represent myself as an object. But suppose that I, or another being, were able to intuit me without the condition of sensibility. The same determinations that now appear to us as changes would then give a cognition containing no representation of time and so none of change. Its empirical reality thus stays, as the condition of all our experiences. Absolute reality is the one thing we cannot grant it, in light of the earlier points. Time is no more than the form that our inner intuition takes*. Take away the special condition of our sensibility and the concept of time disappears too. It does not cling to the objects themselves. It clings only to the subject doing the intuiting.

* I can indeed say that my representations follow one another. That says only that we are aware of them in a time sequence, which is to say, in the form of inner sense. Time is not, for that reason, something in itself, or a determination attached objectively to things.

The reason why this objection is raised so unanimously, even by people who can find nothing convincing to say against the doctrine of the ideality of space, is this.

B 55 They did not hope to prove the absolute reality of space apodictically, because idealism stands in their way. According to idealism, the actual existence of outer objects can’t be strictly proved. Our inner senses, by contrast, have an object (myself and my state), and its actuality is plain straight from consciousness. The former could be a mere illusion. The latter, they thought, is undeniably something actual. What they overlooked is that both belong only to appearance, even though no one may dispute their actuality as representations. An appearance always has two sides. In one, the object is considered in itself, whatever the way of intuiting it. For that very reason, its nature always stays problematic. In the other, we look to the form of intuition of this object. That form is not to be sought in the object itself but in the subject to which the object appears. Even so, it belongs to the appearance of this object really and necessarily.

So time and space are two sources of cognition. Various synthetic cognitions can be drawn from them a priori, as pure mathematics shows brilliantly, above all in its cognitions of space and its relations.

B 56 That is because the two together are the pure forms of all sensible intuition, and for that reason they make synthetic a priori propositions possible. Yet by the very fact that they are mere conditions of sensibility, these a priori sources set their own boundaries. They reach only objects viewed as appearances. They never present things in themselves. Only appearances make up the field where they hold. Outside it they have no further objective use. This reality of space and time, incidentally, leaves the certainty of empirical cognition untouched. Our certainty about it is the same either way: it makes no difference whether these forms necessarily cling to things in themselves or only to how we intuit those things. People who claim absolute reality for space and time, on the other hand, whether as subsisting or merely as inhering, are bound to clash with the principles of experience itself. Take the first choice (commonly the party of the mathematical natural scientists). They then have to accept two eternal and infinite entities that exist on their own and yet are not real things (space and time). These are there, though nothing real is there, merely to contain everything real. Now take the second choice (some metaphysical natural philosophers hold it). Space and time then count for them as relations among appearances (side by side or one after another), relations abstracted from experience.

B 57 Considered in isolation, they are represented only in a confused way. Then they must deny that the doctrines of a priori mathematics are valid for actual things (in space, for instance), or at least deny their apodictic certainty. The reason is that apodictic certainty never comes from the a posteriori. In their view, the concepts we hold a priori of space and time are mere products of imagination. Their source has to be sought in experience. Out of relations abstracted from experience, imagination has made something that contains what they have in common but cannot exist without the restrictions that nature has tied to them. The first group gains this much: the field of appearances is cleared for mathematical claims. But these same conditions badly trip them up when the understanding wants to go past that field. The second group gains something regarding the latter. The representations of space and time cause them no trouble when they judge objects not as appearances but purely by their relation to the understanding. What they cannot do is explain how a priori mathematical cognition is possible, since they have no true, objectively valid a priori intuition. Nor can they make the propositions of experience agree necessarily with those claims.

B 58 Our theory of the true nature of these two original forms of sensibility removes both difficulties.

Lastly, the transcendental aesthetic can contain only these two elements, space and time, and the reason is clear. Every other concept belonging to sensibility presupposes something empirical, even the concept of motion, which unites both. Motion presupposes the perception of something movable. But nothing movable exists in space considered in itself. So the movable has to be something found in space only by experience, and therefore an empirical datum. Likewise the transcendental aesthetic cannot count the concept of change among its a priori data. Time itself does not change. Something in time does. So the concept needs the perception of some existing thing and of the succession of its determinations, and therefore it needs experience.

B 59 § 8 General remarks on the transcendental aesthetic

I. To begin, we must say as plainly as we can what we think about the basic makeup of sensible cognition in general, so as to prevent any misreading of it.

What we meant to say was this. All our intuition is only the representation of appearance. The things we intuit are not what we take them to be in themselves, and their relations are not in themselves as they look to us. If we removed our subject, or even only the subjective makeup of the senses in general, all properties and relations of objects in space and time would vanish, and space and time themselves too. As appearances they can exist not in themselves but only in us. How objects are constituted in themselves, taken apart from this whole receptivity of our sensibility, is something we never learn. All we know is our way of perceiving them. It is peculiar to us, and it need not belong to every being, even though it belongs to every human. We have to do only with this way. Space and time are its pure forms.

B 60 Sensation in general is its matter. The pure forms alone can we cognize a priori, before any actual perception, and that is why they are called pure intuition. Sensation is what makes a cognition one a posteriori, an empirical intuition, as we call it. Pure forms are bound to our sensibility with sheer necessity, no matter what kind of sensations we have. Sensations can differ widely. Say we managed to make this intuition of ours as distinct as it can possibly be. We still would not come nearer to the nature of objects in themselves. For we would still cognize completely only our own way of intuiting, our sensibility, and always under the conditions of space and time that are original to the subject. What objects may be in themselves would never be known to us, however enlightened our cognition of their appearance is, the only thing that is given to us.

To say that our whole sensibility is just a confused representation of things is a falsification of the concepts of sensibility and appearance. It makes the whole doctrine of them useless and empty. On that idea, sensibility contains only what the things have in themselves, but heaped together with marks and partial representations that we don’t consciously sort out.

B 61 Distinct versus indistinct is only a logical difference between representations. It leaves their content alone. Doubtless the concept of right that sound understanding uses holds exactly what the subtlest speculation can unfold from it. In everyday practical use, though, we are not aware of the many representations contained in these thoughts. For that reason the everyday concept can’t be called sensible or said to contain mere appearance. Right can’t appear at all. Its concept lies in the understanding and stands for a property (the moral one) that actions have in themselves. The representation of a body in intuition is different. Nothing in it could belong to an object in itself. All it holds is the appearance of something and the way that thing affects us. We call this receptivity of our faculty of cognition sensibility. Even if we could see through the appearance to its very bottom, sensibility would still be worlds away from cognition of the object in itself.

Leibniz-Wolfian philosophy gave every inquiry into where our cognitions come from, and what they are, a wholly mistaken starting point. It regarded the difference between sensibility and what is intellectual as purely logical. In fact the difference is transcendental.

B 62 It is not only a matter of the form of distinctness or indistinctness. It also concerns origin and content. The consequence is that sensibility does not merely show us the nature of things in themselves indistinctly. It does not show it at all. Take away our subjective makeup and the represented object, with all the properties sensible intuition gave it, is not to be met with anywhere, nor could it be. For that makeup is just what fixes its form as an appearance.

We are used to sorting appearances into two kinds. One kind belongs essentially to their intuition and is valid for any human sense at all. The other kind belongs to it only by chance. The second kind is not valid for sensibility generally, but only for the particular position or organization of this sense or that. The first kind is then said to be cognition that presents the object in itself, and the second to present only its appearance. This distinction, though, is only empirical. Suppose we stop there, as usually happens, and fail to look at that empirical intuition in turn as mere appearance (as we should), so that nothing in it touches any thing in itself. Then our transcendental distinction is lost. We still believe that we cognize things in themselves. Yet everywhere in the world of sense we deal with appearances only.

B 63 This holds even for the deepest investigation of its objects. We would call a rainbow a mere appearance in a sun shower, and call the rain the thing in itself. That is even right, provided the second concept is understood merely physically: as whatever general experience finds determined in intuition in just this way and not otherwise, from every position relative to the senses. But take this empirical thing in general, and ask, without regard to whether it agrees with every human sense, whether it too presents an object in itself (not the raindrops, for those are empirical objects already, as appearances). The question about how the representation relates to the object is then transcendental. Not only are these drops mere appearances. Even their round shape is nothing in itself, and so is the space in which they fall. They are only modifications, or foundations, of our sensible intuition. The transcendental object remains unknown to us.

A second weighty matter for our transcendental aesthetic is this: it should not merely earn some goodwill as a plausible hypothesis. It should be as certain and beyond doubt as any theory can be asked to be that is meant to serve as an organon. To make this certainty fully evident, we will choose a case.

B 64 Through it, the validity of the theory can become obvious. It can also make clearer what was said in § 3.

Suppose space and time were objective in themselves and conditions for the possibility of things in themselves. Then, to begin with, a great many apodictic and synthetic propositions arise a priori from both, above all from space, which we will therefore use as our main example. Geometry’s propositions are cognized as synthetic a priori and with apodictic certainty. So I ask: where do you get such propositions? What does our understanding stand on, to reach truths that are so absolutely necessary and universally valid? The only routes are concepts and intuitions, and each of these is given either a priori or a posteriori. Empirical concepts, and the empirical intuition they are based on, can give only a synthetic proposition that is itself empirical, a proposition of experience. Such a proposition can never contain necessity and absolute universality, yet those are exactly what mark all geometrical propositions. That leaves the a priori kind as the only means left: to reach such cognitions through concepts alone or through a priori intuitions. Here it is clear that concepts alone give no synthetic cognition, only analytic.

B 65 Take the proposition that two straight lines can enclose no space, so that no figure is possible, and try to get it out of the concept of straight lines together with the number two. Or take the claim that three straight lines make a figure possible, and try the same with nothing but those concepts. All your effort is wasted. You are forced to run to intuition, as geometry always does. So you give yourselves an object in intuition. What sort of intuition is it, though, pure and a priori or empirical? Were it empirical, it could never yield a universally valid proposition, let alone an apodictic one, because experience cannot provide that. So you must give your object in intuition a priori and build your synthetic proposition on it. Now suppose you had no capacity to intuit a priori. Suppose also that this subjective condition were not, in its form, at once the universal a priori condition for the very possibility of the object of this (outer) intuition. Suppose, too, that the object (the triangle) existed in itself, unconnected to you as a subject. Then how could you claim that whatever your own subjective conditions necessarily involve in constructing a triangle must hold necessarily of the triangle in itself? You could not add anything new (the figure) to your concepts (of three lines).

B 66 That new thing would then have to turn up in the object as a matter of necessity, because the object is given ahead of your cognition, not by means of it. Suppose space, and time too, were not a mere form of your intuition, containing the a priori conditions under which alone things can be outer objects for you (objects that are nothing in themselves without these subjective conditions). Then you could establish nothing at all synthetically, a priori, about outer objects. It is therefore not merely possible, or probable, but certain, that space and time are nothing but subjective conditions of all our intuition. They are the necessary conditions of all experience, outer and inner. In relation to them all objects are mere appearances, not things given for themselves in this way. About their form, therefore, much can be said a priori, but never the slightest about the thing in itself that may lie beneath these appearances.

II. One remark does a lot to back up this theory. The theory says outer sense and inner sense are ideal, so every object of the senses is a mere appearance. Here is the remark. Whatever in our cognition counts as intuition holds relations and nothing else. (I set aside feelings of pleasure and pain, and the will, because those aren’t cognitions at all.) There are relations among places within an intuition, which gives us extension.

B 67 There are changes of place, which give us motion. And there are the laws that fix those changes, which give us the moving forces. None of this shows us what is actually present in a place. It doesn’t show what the things themselves do besides move about. Bare relations can never get us to a cognition of a thing in itself. So we should conclude the following. Outer sense hands us only representations of relations. All it can carry, then, is how an object stands to the subject, within the subject’s representation. It can’t carry the inner nature that belongs to the object by itself. The same goes for inner intuition. For one thing, the representations of the outer senses are the real material we fill our mind with. But there is more to it. We place those representations in time. Time comes before our awareness of them in experience, and it lies beneath our placing of them in the mind, as a formal condition. And time already holds relations: of one thing after another, of things at once, and of what lasts while other things follow one another (the permanent). Now whatever can precede every act of thinking something, as a representation, is intuition. When intuition holds only relations, what we have is its form. This form presents nothing unless something is placed in the mind. So the only thing it can be is the way the mind gets affected by its own activity.

B 68 That activity is this very placing of its representation. Thus the mind is affected by itself. Put differently, this is inner sense, taken as to its form. Anything a sense represents is, in that respect, always an appearance. So either we should not grant inner sense at all, or the subject that is its object can show up through it only as an appearance. It couldn’t show up the way it would judge itself to be, supposing its intuition were pure self-activity, that is, intellectual. All the difficulty here comes down to one question: how can a subject look inward at itself? But every theory faces that difficulty. Being conscious of oneself (apperception) is just the bare representation of the I. Suppose that representation alone gave the subject everything manifold in it, by the subject’s own activity. Then inner intuition would be intellectual. In human beings, this consciousness needs an inner perception of the manifold that was already given to the subject. How that manifold gets into the mind without any spontaneity has to be called sensibility, to mark the difference. Now take the capacity to become conscious of oneself. If it is to hunt for whatever lies in the mind (to apprehend it), it has to affect the mind. That is the only way it can bring about an intuition of itself. But the form of this intuition already lies in the mind as a ground. It fixes how the manifold sits together in the mind.

B 69 It does this within the representation of time. So the mind looks at itself, not as it would present itself straight from its own activity, but as it is affected from within. It sees itself as it seems to itself, not as it is.

III. When I say that intuition in space and time represents two things as they affect our senses, that is, as they appear, I do not mean that these objects are mere illusion. The two things are the outer objects and the mind’s intuition of itself. For when something appears, its objects are always taken as really given, and so are the properties we assign them. The one catch is this. Suppose a property hangs only on how the subject intuits, within the relation between the given object and the subject. Then we tell the object as appearance apart from that same object as it is in itself. So I am not claiming that bodies only seem to exist outside me, or that my soul merely seems to be given in my consciousness of myself. I claim that space and time owe their character to how I intuit, not to these objects in themselves. I place both bodies and soul by that character, as the condition of their existence. I would have only myself to blame if I made illusion out of what I should count as appearance*.

B 70 But that doesn’t happen under our principle that all our sensible intuitions are ideal. Rather, if you give those forms of representation objective reality, you cannot avoid turning everything into mere illusion. Suppose you treat space and time as properties that could only exist if they were found in things in themselves. Now look at the absurdities you get tangled in. You end up with two infinite things. They aren’t substances, and they aren’t anything really belonging to substances, and yet they exist.

B 71 They are even the necessary condition for the existence of all things. And they would stay put even if every existing thing were taken away. With all that on the table, nobody can fairly criticize good Berkeley for demoting bodies to mere illusion. Worse, our own existence would turn into pure illusion along with time. Our existence would then hang on the self-standing reality of a non-thing like time. No one so far has been guilty of such an absurdity.

* We can ascribe predicates of appearance to the object itself, as it relates to our sense. The red color of a rose, or its smell, is an example. Illusion, though, can never be treated as a predicate of the object. The reason is exactly that illusion hands the object, taken alone, something that belongs to it only through the senses, or through the subject generally. The two handles people first gave Saturn are an example. Whatever is never in the object by itself, but always in how it stands to the subject, and can’t be pulled apart from the representation of it, is appearance. So it is right to give the objects of the senses, as such, the predicates of space and time. There is no illusion in that. It is different when I credit the rose with redness in itself, or Saturn with handles, or all outer objects with extension in themselves. That happens when I overlook how these objects stand to the subject in some definite way, and fail to hold my judgment to that. Only then does illusion arise.

IV. In natural theology we imagine an object that is no object of intuition for us whatever. More than that, it can’t be an object of sensible intuition even for itself. So people take great care to strip the conditions of time and space away from all of its intuition. (Everything it cognizes must be intuition, not thinking, since thinking always shows limits.) But by what right do we do that? We would already have turned space and time into forms of things in themselves. They would be forms that stay, as a priori conditions for the existence of things, even if the things were removed. They would hold for all existence whatever, so they would hold for God’s existence too. Suppose we refuse to treat them as objective forms of everything. Then we have one choice left.

B 72 We must treat them as forms that belong to the subject, to our way of intuiting, outer and inner alike. We call this way of intuiting sensible because it isn’t original. An original intuition would be one in which the object’s very existence gets given. (As far as we could tell, only the original being could have that.) Ours depends instead on the object’s existence. It is possible only when the object affects the subject’s capacity for representation.

We also needn’t limit the intuiting that happens in space and time to the sensibility of human beings. Perhaps every finite thinking being has to match human beings here. (We can’t settle that.) Even so, being universal doesn’t stop it from being sensibility. The reason is that this intuition is derived (intuitus derivativus) and not original (intuitus originarius). So it is not intellectual intuition. As just argued, only the original being seems to have intellectual intuition. It never belongs to a being that is dependent, in its existence as well as in its intuition (the intuition that fixes its existence relative to given objects). Still, we should count that last remark as an illustration of our aesthetic theory only, and not as a proof.

B 73 Conclusion of the Transcendental Aesthetic

Here we have one piece of what we need in order to solve the general problem of transcendental philosophy: how are synthetic propositions a priori possible? The piece is the pure intuitions a priori, space and time. Say we want to leave a given concept behind in a judgment a priori. In these intuitions we meet what the concept lacks. It can be discovered a priori in the intuition that fits the concept, and joined to the concept synthetically. For that very reason, though, such judgments reach no further than objects of the senses. They hold only for objects of possible experience.