<a1> [B33] The Transcendental Doctrine of Elements

Knowledge can relate to objects in various ways and through various intermediaries. Intuition is that through which it is immediately related to objects, and to which all thought is directed as the intermediary of knowledge. But intuition takes place only in so far as the object is given to us. Again, in the case of us humans at least, an object can be given to us only if it affects the mind in a certain way. Receptivity, or the capacity to acquire representations through the way in which we are affected by objects, is called sensibility. So it is by means of sensibility that objects are given to us, and it is sensibility alone that provides us with intuitions. But intuitions are thought through the understanding, and it is from the understanding that concepts arise. However, all thought must ultimately relate to intuitions, whether directly or indirectly, by virtue of certain properties. So in the case of us human beings, thought relates to sensibility, because no object can be given to us in any other way.

<a2> [B34] The effect of an object on the faculty of representation, in so far as we are affected by it, is sensation. An intuition which is related to the object through sensation is called empirical. The undetermined object of an empirical intuition is called an appearance.

<a3> That in an appearance which corresponds to sensation, I call its matter, and that which enables the multiplicity of the appearance to be organised in particular relationships, I call the form of the appearance. That which is essential for sensations to be organised and put into a particular form, cannot itself be a sensation. Therefore, while the matter of all appearance is indeed given to us only aposteriori, the whole of its form must lie ready for it in the mind apriori, and hence its form can be considered separately from all sensation.

<a4> I call any representation pure (in the transcendental sense) if it contains nothing that belongs to experience. So the pure form of sensory intuition in general will be found apriori in the mind, and through it all the multiplicity of appearances will be intuited in particular relationships. This pure form of sensibility is also itself called pure [B35] intuition. Thus if I abstract from the representation of a body everything that the understanding thinks about it (substance, force, divisibility, etc.), and also everything in it that belongs to sensation (impenetrability, hardness, colour, etc.), I am still left with something from this empirical intuition, namely extension and shape. These belong to pure intuition, which exists apriori in the mind as a pure form of sensibility, even when there is no actual object of the senses, or any actual sensation.

<a5> I call a science of all the principles of apriori sensibility the transcendental aesthetic.*

• either let the term revert to its original meaning, and reserve it for a doctrine which is a genuine science — in which case we would come closer to the terminology and meaning of the ancients, who were renowned for their division of knowledge into what is known by the senses (aestheta) and what is known by the intellect (noeta);
• or share the term between speculative philosophy and the critique of taste, so that the term ‘aesthetic’ can be taken both in a transcendental sense, and as having a psychological meaning.]

<a6> There must be such a science as the Transcendental Aesthetic, and it [B36] constitutes the first part of the Transcendental Doctrine of Elements. It is complemented by the second part, which contains the principles of pure thought, and is called the Transcendental Logic.

<a7> So in the Transcendental Aesthetic, we shall:

1. isolate sensibility, by abstracting everything which the understanding thinks in it through its concepts, so that nothing remains except empirical intuition; then
2. separate off from empirical intuition everything which belongs to sensation, so that nothing remains except pure intuition and the mere form of appearances — which is all that sensibility can supply apriori.

In the course of this investigation, it will emerge that there are two pure forms of sensory intuition which serve as apriori principles, namely space and time. I shall now proceed to a consideration of these.

<a8> [B37] The Transcendental Aesthetic

Outer sense is a property of our mind, and it is the means by which we represent to ourselves objects as outside us, and as occupying a single space. It is in space that their shape, size, and relations with each other are, or can be determined. Inner sense is the means by which the mind intuits itself or its inner state. It does not supply any intuition of the soul itself as an object, but it is a determinate form, namely time, which is essential for the soul to be able to intuit its inner state. Everything which belongs to inner determinations is represented in relations of time.

<a9> Time cannot be intuited externally, any more than space can be intuited as something internal to us. So what are space and time? Are they actual beings? Are they merely determinations or even relations of things, although ones which would still intrinsically belong to things even if they were not intuited? Or do they belong only to the form of intuition, and hence to the [B38] subjective nature of our minds, so that without this nature, spatio-temporal predicates could not be ascribed to things at all?

<a10> In order to answer these questions, I shall begin by expounding the concept of space. By exposition I mean the clear (though not complete) representation of what belongs to a concept. An exposition is metaphysical when it contains what shows the concept as given apriori.

<a11> 1. Space is not an empirical concept abstracted from outer experiences. For the representation of space must already be presupposed in order for me to be able:

• to relate certain sensations to something outside me (in other words, to something in a different part of space from that in which I find myself); and
• to represent them as separated from or next to one another, and hence not merely as different from each other, but also as in different places.

So the representation of space cannot be obtained empirically from the properties of outer appearance. Rather, this outer experience itself becomes possible only through the representation of space.

<a12> 2. Space is a necessary apriori representation, which is presupposed by all outer intuitions. You can never form a representation of space not existing, though you can easily think that it is empty of objects. [B39] So it must be regarded as the precondition for the possibility of appearances, and not as a determination depending on them. It is an apriori representation, which necessarily grounds outer appearances.

<a13> 3. Space is a pure intuition, and not a wide-ranging or (as is said) a universal concept of relations of things in general. For, first, you can represent only one single space, and if you talk of different spaces, you really mean only different parts of one and the same unique space. Secondly, these parts cannot exist before the single, all-embracing space, as, so to speak, building-blocks from which it can be assembled together as a whole. Rather these parts can be thought only as in space.

<a14> Space is essentially unitary. The multiplicity it contains, and hence also the universal concept of spaces in general, depends wholly on limitations of unitary space. From this it follows that, as far as space is concerned, all concepts of it are based on an apriori intuition, which is not empirical. So it also follows that no geometrical axioms (e.g. that in a triangle, the sum of two sides is greater than the third), can ever be deduced from the universal concepts of line and triangle, but only from intuition — and indeed deduced apriori with demonstrative certainty.

<a15> 4. Space is represented as an infinite given quantity. Now it is true that every concept [B40] must be thought as a representation which is contained in an infinite number of different possible representations as their common characteristic. So the concept contains these representations in the sense that they come under it. But no concept, as such, can be thought as containing an infinite number of representations in itself. However, this is just how space is thought, since all parts of space, right down to infinity, exist simultaneously. Thus the originative representation of space is an apriori intuition, and not a concept.

<a16> §3

By a transcendental exposition, I mean explaining a concept as a principle which enables us to understand the possibility of further synthetic apriori knowledge. In order to fulfil this purpose, it is required:

1. that such knowledge does actually flow from the given concept; and
2. that the possibility of this knowledge presupposes a given way of explaining the concept.

<a17> Geometry is a science which determines the properties of space synthetically, and yet also apriori. So what must the representation of space be, for such knowledge of it to be possible? It must be an originative intuition, and not just a concept. For [B41] no propositions which go beyond a concept can be deduced from it alone — and as I showed in the Introduction (section 5), the propositions of geometry do go beyond geometrical concepts. But this intuition must be found in us apriori, that is, before any perception of an object. Hence it must be a pure, and not an empirical intuition. For all geometrical propositions are demonstratively certain — that is, we cannot be conscious of them without at the same time being conscious of their necessity. For example, propositions like ‘Space has only three dimensions’ cannot be empirical or experiential judgments, nor can they be deduced from such judgments, as I showed in the Introduction (section 2).

<a18> But how can the mind contain an outer intuition, which exists before its objects themselves, and in which the concept of its objects can be determined apriori? Obviously, the only way this is possible is because the intuition is located in the subject of perception, as the capacity of the subject to be affected by objects, but only so far as their form is concerned. It is the means by which the mind obtains a direct representation of its objects, i.e. intuition. Consequently, the intuition of space is merely the form of outer sense in general.

<a19> So my explanation is the only one which makes it comprehensible how it is possible for geometry to consist of synthetic apriori knowledge. Any other kind of explanation which fails to achieve this is clearly distinguishable from mine by virtue of this very failure, even if it seems to bear some similarity to mine in other respects.

<a20> [B42] Conclusions from the above concepts

(a) Space does not represent any property of things in themselves, nor does it represent them in terms of their mutual relationships. In other words, it does not represent any determination of things which inheres in objects themselves, and which remains even when you leave out of account any subjective preconditions for intuition. For no determinations of things, whether absolute or relative, can be intuited before the existence of the things in which they inhere, and hence they cannot be intuited apriori.

<a21> (b) Space is nothing other than the form of all appearances of outer sense. In other words, it is the precondition for sensibility on the side of the subject, and it alone is what makes outer intuition possible for us. The receptivity of the subject, that is, its capacity to be affected by objects, necessarily precedes any intuitions of these objects. Consequently, it is easy to understand how the form of all appearances can be given in the mind before any actual perceptions, and hence apriori. It is also easy to understand how space, as a pure intuition in which all objects must be determined, can contain principles of the relations between objects before any experience.

<a22> So it is only from our standpoint as human beings that we can talk of space, extended beings, and so on. If we go beyond the preconditions which are in ourselves as subjects, and which are necessary for us to have outer intuition, the representation of space [B43] has nothing at all to refer to. The predicate of spatiality is attributable to things only in so far as they appear to us, that is, only in so far as they are objects of sensibility. Space, as the all-present form of this receptivity, which we call sensibility, is a necessary precondition for all relationships in which objects are intuited as outside us. If we leave these objects out of account, there remains a pure intuition called ‘space’. We cannot turn the preconditions which are peculiar to sensibility into preconditions for the possibility of things, but only into preconditions for the possibility of their appearances.

<a23> Therefore we can indeed say that space encompasses all things that can appear to us as external; but not that it encompasses things in themselves, whether they are intuited or not, or even whatever subject they are intuited by. For we can make no judgment at all about the intuitions of other thinking beings, and we cannot tell whether or not they are bound by the same preconditions which limit our intuition, and which are universally valid for us.

<a24> If we add the limited scope of a judgment to the concept of its subject, the judgment then becomes valid unconditionally. For example, the proposition ‘All things are related to each other in space’ is valid with the proviso that these things are taken as objects of our sensory intuition. If I now add the precondition to the concept, and say: ‘All things as outer appearances are related to each other in space,’ this rule is valid universally and without any limitation of scope.

<a25> So my [B44] exposition teaches 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 they are considered in themselves through reason, that is, without reference to the properties of our sensibility. I therefore assert the empirical reality of space with regard to all possible outer experience, but also its transcendental ideality. This means that space is nothing as soon as we forget that it is the precondition of the possibility of all experience, and take it as something which things in themselves depend on.

<a26> Apart from space, there are no other subjective representations related to something outer, which can be called apriori objective. For none of them give rise to synthetic apriori propositions in the way that intuition in space does (see §3, above). To be more precise, they have no ideality at all, even though they have it in common with the representation of space, that they belong merely to the subjective properties of the kind of senses we have. For example, sight, hearing, and touch give us sensations of colours, sounds, and warmth; but since these are merely sensations, and not intuitions, they do not by themselves provide us with knowledge of any object — least of all, apriori knowledge.

<a27> [B45] The purpose of this comment is simply to prevent anyone from making the mistake of using completely inappropriate examples to illustrate the ideality of space which I assert here. For instance, colours, taste, etc. are rightly considered not to be properties of things, but merely alterations in us as subjects; and they can even be different in different people. In this case, something which is itself ultimately only an appearance, e.g. a rose, is taken by the empirical understanding for a thing in itself, despite the fact that, in respect of its colour, it can appear differently to every observer. By contrast, the transcendental concept of an appearance in space is a critical reminder that absolutely nothing intuited in space is a thing in itself, and that space is not a form of things which belongs to them as they are in themselves. Rather, objects as they are in themselves are completely unknown to us, and what we call outer objects are nothing other than mere representations of our sensibility. Their form is space, but space does not and cannot give us any knowledge of their true correlate, namely the thing in itself. But in experience no question is ever asked about the thing in itself.

<a28> [B46] The Transcendental Aesthetic

1. Time is not an empirical concept which has been abstracted from any experience. For even the simultaneous or successive existence of things would not be perceived, if the representation of time did not underlie it apriori. Only on the presupposition of time can you represent things as existing at one and the same time (simultaneously) or at different times (successively).

<a29> 2. Time is a necessary representation, which is the foundation of all intuitions. It is universally true of appearances that you cannot remove time itself; but you certainly can take appearances away from time. So time is given apriori. In time alone is any actuality of appearances possible. Appearances could all be entirely annihilated; but time itself (as the universal precondition of their possibility) cannot be removed.

<a30> [B47] 3. This apriori necessity is also why it is possible for there to be self-evident axioms about the properties of time, or axioms about time in general — that it has only one dimension; and that different times are not simultaneous, but successive (just as different spaces are not successive, but co-existent). These axioms could not be abstracted from experience, since experience would provide neither strict universality nor self-evident certainty. We could only say, ‘This is what we all learn from perception,’ but not ‘This is how things must be.’ These axioms serve as rules, under which alone experiences are possible; and they teach us before experiences, and not through perception.

<a31> 4. Time is not a wide-ranging concept (or ‘universal’ concept, as it is called), but a pure form of sensory intuition. Different times are only parts of one and the same time. But a representation which can be given only through a single object is an intuition. Furthermore, the proposition that different times cannot exist simultaneously could not be deduced from a single universal concept. The proposition is synthetic, and cannot be deduced from concepts alone. Therefore it is contained immediately in the intuition and representation of time.

<a32> 5. The endlessness of time means merely that all determinate tracts of time are possible only through [B48] delimitations of a single time, from which they originate. Consequently, the originative representation Time must be given as undelimited. But the representation of a whole cannot be given through concepts, if its parts themselves (and every quantity of an object) can be represented determinately only through delimitation, since concepts contain only partial representations. Rather, the foundation of the parts must be immediate intuition.

<a33> §5

For a transcendental exposition, I can refer to §4, paragraph 3, where, in order to save time, I included what is essentially transcendental in the section on the metaphysical exposition.

<a34> Here I shall add that the concept of change, and with it the concept of motion (as change of position) is possible only through and in the representation of time. If this representation were not an apriori intuition (of inner sense), no concept whatever could make intelligible the possibility of a change in one and the same object, since it consists in a combination of contradictorily opposed predicates (for example, one and the same thing being in a place, and not being in the same place). Two [B49] contradictorily opposed determinations can be met with in a single thing only in time, namely one after the other. So our concept of time explains the possibility of all the synthetic apriori knowledge included in the general doctrine of motion — which is by no means unfruitful.

<a35> §6

(a) Time is not something which exists in itself, or belongs to things as an objective determination. Consequently, it would not remain if you left out of account all the subjective preconditions of the intuition of things. For in the first case, it would be something actual, but without having an actual object. As for the second case, it could not precede objects as their condition, or be known and intuited apriori through synthetic propositions, because it would be a determination or ordering which belonged to things themselves. But it can indeed be known apriori, if time is nothing other than the subjective condition for any intuition to come into existence within us. For thus this form of inner intuition can be represented before objects are represented, and hence apriori.

<a36> (b) Time is nothing other than the form of inner sense, that is, of the intuition of our self, and of our inner state. For time cannot be any determination of outer appearances. It does not belong [B50] to a shape, or a position, etc., but instead it determines the relationship between representations in our inner state. And precisely because this inner intuition provides nothing which has a shape, we try to make up for this lack through analogies. We represent the sequence of time as a line continuing without end, in which the multiplicity consists of a series which has only one dimension. We use the properties of this line to draw conclusions about all the properties of time, except for the one property, that the parts of the line exist simultaneously, whereas the parts of time always exist successively. From this too it is obvious that the representation of time is itself an intuition, because all its properties can be expressed in an outer intuition.

<a37> (c) Time is the universal apriori formal precondition of all appearances. Space, as the pure form of all outer intuition, is limited to being the apriori precondition merely of outer appearances. However, all representations, whether or not they have external things as their objects, belong in themselves to our inner state, as determinations of the mind. But this inner state is subject to the formal conditions of inner intuition, and therefore to time. Consequently, time is a universal apriori precondition of all appearance. More precisely, it is the immediate precondition of inner appearances (of our souls), and through inner appearances it is also the mediate precondition of outer appearances. [B51] If I can say apriori that all outer appearances are in space, and determined apriori in accordance with the properties of space, then the foundation of inner sense allows me to say quite universally that absolutely all appearances (i.e. all objects of the senses) are in time, and necessarily conform to the properties of time.

<a38> Time is nothing, if we take objects as they might be in themselves — that is, if we leave out of account our way of inwardly intuiting ourselves, and also of including outer intuitions within our faculty of representation by means of this inner intuition. Time has objective validity only in relation to appearances, because these are already things which we take as objects of our senses. However, it is no longer objective if we leave out of account the sensory nature of our intuition (and hence the way of representing things which is peculiar to us humans), and start talking about things as universals. So time is only a subjective condition of our (human) intuition, which is always sensory — that is, we have intuitions only in so far as we are affected by objects. In itself, outside the subject, time is nothing. Nevertheless, it is necessarily objective in relation to all appearances, and hence also to all things which can enter into our experience. We cannot say, ‘All things are in time,’ because [B52] every kind of intuition of things is left out of account in the concept of a thing in general. But intuition is the essential precondition for time to belong to the representation of objects. Now if this precondition is added to the concept, we will then be saying, ‘All things, as appearances (objects of sensory intuition) are in time.’ And this formulation of the axiom will be sound, and objectively true and universal apriori.

<a39> So what I have said implies the empirical reality of time — in other words, its objective validity in relation to all objects which might ever be given to our senses. And since our intuition is always sensory, no object can ever be given to us in experience which does not come under the precondition of time. On the other hand, I dispute any claim of time to absolute reality — that is, as belonging to things intrinsically, as a precondition or essential property, without any reference to the form of our sensory intuition. The essential properties of things in themselves can never be given to us through our senses. This is what the transcendental ideality of time consists in. It means that, if you leave out of account the subjective conditions of sensory intuition, time is nothing at all, and it cannot be counted as either underlying or inhering in objects as they are in themselves (without their relationship to our intuition).

<a40> But the ideality of time, [B53] like that of space, is utterly different from the illusory nature of sensation. In the case of sensation, it is assumed that the appearance itself, in which the predicates of space and time inhere, has objective reality. But in the case of space and time, there is no question of objective reality, except in so far as it is merely empirical — that is to say, except in so far as the object itself is regarded as merely an appearance. On this point, see the first Section, above.

<a41> §7

My theory allows time empirical reality, but refuses it absolute and transcendental reality. However, intelligent people have raised an objection to this theory so unanimously, that I conclude it must naturally occur to any reader who is unused to these studies. This objection is as follows. There actually are alterations — this is proved by the change in our own representations, even if you deny the genuineness of all outer appearances, together with their alterations. But alterations are possible only in time; therefore time is something actual.

<a42> There is no difficulty in providing an answer. I accept the whole argument. Time is certainly something actual, namely the actual form of inner intuition. Thus it has subjective reality with respect to inner experience — that is, I actually have the representation [B54] of time and of my determinations in it. So time is to be considered actual — not as an object, but as the way in which I represent myself as an object. But if I could intuit myself, or some other being could intuit me, without this precondition of sensibility, these very same determinations, which we now represent as alterations, would provide a kind of knowledge which contained no representation of time at all, and hence none of alteration either. But time still has empirical reality, as the precondition of all our experiences. It is only absolute reality it cannot be allowed to have, for the reasons given above. Time is nothing other than the form of our inner intuition.*

If we take away from time the special precondition of our sensibility, the concept of time disappears with it, since it does not inhere in objects themselves, but merely in the subject which intuits them.

<a43> I shall now give the reason why this objection has been made so unanimously, even though those who make it have nothing [B55] enlightening to say against the thesis of the ideality of space. They could not hope to establish the absolute reality of space with demonstrative certainty, because they are confronted by idealism, according to which the actuality of outer objects is incapable of strict proof. By contrast, the actuality of the object of our inner sense (my self and my state) is directly obvious through consciousness. Outer objects could be nothing but an illusion; whereas the object of inner sense is undeniably something actual (in their opinion, that is).

<a44> However, they overlooked the fact that both are in the same position. In neither case can their actuality as representations be disputed, but they both belong only to appearance. An appearance always has two sides. On the one side, the object is considered as it is in itself — but since no attention is paid to the way in which it is intuited, the nature of the object always remains problematic. On the other side, the form of the intuition of the object is taken into account. However, the form is to be found, not in the object as it is in itself, but in the subject to which the object appears. Nevertheless, the form of the intuition actually and necessarily belongs to the appearance of the object.

<a45> So time and space are two sources of knowledge, which give rise to synthetic apriori knowledge of various sorts. The most striking example is mathematics, as far as concerns knowledge of space and its properties. [B56] Taken together, both time and space constitute the forms of all sensory intuition, and as such they make synthetic apriori propositions possible. But these sources of apriori knowledge determine their own limits, by virtue of the fact that they are no more than preconditions of sensibility. These limits are that they apply to objects only in so far as objects are considered as appearances — they do not represent things in themselves. The scope of their validity is confined to appearances, and if we go beyond appearances, there is no further objective use for these sources of knowledge.

<a46> Further, this way in which space and time are real leaves the certainty of experiential knowledge untouched, since we are just as convinced of it, whether these forms necessarily belong 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 self-subsistent entities, or merely as inhering in things in themselves) must themselves come into conflict with the principles of experience.

<a47> Those who opt for the first alternative (which is the line usually taken by mathematical physicists), are committed to two eternal and infinite self-subsistent non-things (space and time), which are there (yet without there being anything actual) only in order to include everything actual within themselves.

<a48> Those who take the other line (as do some metaphysical physicists), hold that space and time are [B57] relations between appearances (simultaneous and successive respectively), which are abstracted from experience, and represented only confusedly in the process of abstraction. Therefore they must deny apriori mathematics any validity, and at least any demonstrative certainty, when it is applied to actual things (things in space, for example), since demonstrative certainty can never be established aposteriori. On this view, the apriori concepts of space and time are merely products of the imagination, and their source must actually be looked for in experience. The imagination has used the relations abstracted from experience to construct something which does indeed contain what is common to them, but which cannot be established without the restrictions which nature has attached to them.

<a49> The first group have the upper hand in as much as they do not prevent mathematical assertions from being applicable to the world of appearances. On the other hand, when they want to take their understanding beyond the world of appearances, they are completely nonplussed by the above restrictions.

<a50> The second group have the upper hand as far as the latter point is concerned, because the representations of space and time do not prevent them from judging objects, not as appearances, but merely in relation to the understanding. On the other hand, they cannot provide any foundation for the possibility of apriori mathematical knowledge (since they lack a true and objectively valid apriori intuition), nor can they find any necessary connection which brings experiential propositions into harmony with the claims of mathematics.

<a51> My theory [B58] avoids the difficulties faced by both the above groups, by giving a true account of the nature of the two originative forms of sensibility.

<a52> Finally, it needs to be shown that the Transcendental Aesthetic cannot contain any more than these two components, namely space and time. This is obvious, because all other concepts which belong to sensibility presuppose something empirical. This is true even of the concept of motion, which is a combination both of the apriori and of the empirical. The concept of motion presupposes the perception of something movable. But the concept of space, considered in itself, does not contain the concept of anything movable. Consequently, the movable must be something which is found in space only through experience, and hence given empirically.

<a53> For the same reason, the Transcendental Aesthetic cannot include the concept of alteration among its apriori data, since time itself does not alter, but only something which is in time. The concept of alteration requires the perception of some being or other, and of the succession of its determinations — and this can be supplied only by experience.

<a54> [B59] §8

In order to avoid any misunderstanding, it is first necessary for me to explain, as clearly as possible, my opinion as to the fundamental nature of sensory knowledge in general.

What I have meant to say is that all our intuition is nothing other than the representation of appearance. The things we intuit are not, in themselves, the kind of things we intuit them as being; nor do their properties, in themselves, have the same nature as appears to us. If we took away ourselves as subjects, or even only the subjective nature of the senses in general, then the whole nature and all the properties of objects in space and time, and even space and time themselves, would disappear. Since they are appearances, they cannot exist as things in themselves, but only in us. It remains entirely unknown to us what objects are like in themselves and independently of all this receptivity of our sensibility. All we know is our way of perceiving them, which is peculiar to us; and although it is shared by all humans, it is not necessarily shared by other beings. But here we are concerned only with humans.

<a55> Space and time are the [B60] pure forms of human perception, and sensation in general is its matter. Only the forms can be known apriori, that is, before all actual perception; and that is why this knowledge is called pure intuition. The matter is the component of our knowledge by virtue of which it is called aposteriori knowledge, that is, empirical intuition. The forms inhere in our sensibility with absolute necessity, whatever kind of sensations we have, whereas our sensations can be very different from one another.

<a56> Even if we could raise the distinctness of our intuitions to the highest degree, this would not bring us any closer to the nature of objects in themselves. Whatever happened, we would have a complete knowledge only of our manner of intuition, that is, of our sensibility; and this would still come under the preconditions of space and time, which have their ultimate source in the subject. We could still never know what objects might be in themselves, since even the clearest knowledge is only of their appearance, which is all that is given to us.

<a57> According to the Leibniz-Wolff philosophy, the whole of our sensibility is nothing but the confused representation of things, which includes solely what belongs to things as they are in themselves, but only through an accumulation of characteristics and partial representations which we cannot consciously distinguish. However, this adulterates the concept of sensibility and appearance, and makes the whole of epistemology null and void. The distinction between confused [B61] and distinct representations is purely logical, and has nothing to do with content.

<a58> It is no doubt the case that the concept of right possessed by anyone with a sound understanding contains all that the subtlest speculation can draw out of it, except that in its ordinary and practical use, we are not conscious of the multiplicity of representations contained in this thought. But this does not allow us to say that the ordinary concept is sensory, and contains merely an appearance. The right cannot ‘appear’ at all. Rather, its concept is to be found in the understanding, and it represents a property (the moral property) of actions, and it belongs to them as they are in themselves. By contrast, the representation of a body in intuition contains nothing at all which could belong to an object in itself, but merely the appearance of something, and the way in which we are affected by it. This receptivity of our faculty of knowledge is called ‘sensibility’, and it remains worlds apart from knowledge of the object in itself, even if we could see right through to the innermost depths of the appearance.

<a59> The Leibniz-Wolff philosophy has therefore sent all investigations into the nature and origin of our knowledge in entirely the wrong direction, by treating the difference between sensibility and intellectual knowledge as merely a logical one. But the difference is obviously transcendental, and it depends, not simply on the formal question of whether they are distinct [B62] or confused, but on the difference between the origin and content of each. It is not that sensibility gives us confused knowledge of the nature of things in themselves, but that it gives us no knowledge of them at all. Once we take away the subjective nature of our sensibility, nothing at all is, or can be, left of the object represented, or of the properties our sensory intuition attributes to it, since it is precisely this subjective nature of our sensibility that determines the form of the object as an appearance.

<a60> In appearances, we normally make a perfectly good distinction between what inheres in the intuition of them essentially, and hence is universally valid for the senses of every human being, and what belongs to them only contingently. The contingent element is not valid of the universal properties of sensibility, but only of a particular disposition or structure of this or that sense. So it is normally said that the first kind of knowledge represents the object in itself, and the second only its appearance. However, this distinction is only empirical. People usually stick with it, and fail to see (as they should) that the empirical intuition is in its turn merely an appearance, so that it contains nothing at all that belongs to any thing in itself. When this happens, my transcendental distinction is lost, and we end up believing that we know things in themselves, even though we never (in the world of the senses) have any dealings with anything other than appearances, however deeply we research into [B63] their objects.

<a61> For example, we would certainly call a rainbow in a sunny shower a mere appearance, and the rain a thing in itself. This is acceptable, as long as we understand the concept of a thing in itself merely in the physical sense, as that which is determined in intuition just this one way, in all our experience, and irrespective of its situation relative to our senses. But if we take this empirical object as a universal, that is, ignoring its conformity with all human senses, we can ask whether it represents a thing in itself. (And here I am not talking about the raindrops, since they are surely empirical objects, by virtue of being appearances.) This question is the transcendental one about the relation between a representation and its object. Not only are the raindrops mere appearances, but also their round shape, and even the space within which they fall, are nothing in themselves, but mere modifications or prerequisites of our sensory intuition. But the transcendental object remains unknown to us.

<a62> The second major concern of my Transcendental Aesthetic is that it should not gain a certain amount of favour merely as a plausible hypothesis. Rather, it should be as certain and indubitable as could ever be required of a theory which is to serve as an instrument of the understanding. In order to make the reader completely convinced of its certainty, I shall take a case in which its validity can become obvious, [B64] and which can serve to clarify what I said in §3.

<a63> Let us just suppose that space and time were objective in themselves, and preconditions for the possibility of things in themselves. For a start, it appears that both give rise to a large number of demonstrably certain synthetic apriori propositions. Since this is especially true of space, I shall use space as my main example in this investigation.

<a64> Given that the propositions of geometry are synthetic apriori and known with demonstrative certainty, I ask the following question: Where do you get such propositions from, and what does our understanding depend on, in order to attain such utterly necessary and universally valid truths? The only way is through concepts or through intuitions, and both are given either apriori or aposteriori. Empirical concepts, along with the empirical intuition on which they are based, cannot yield any synthetic proposition other than one which is also merely empirical, that is, an experiential proposition. Consequently it cannot contain any necessity or absolute universality — yet these are precisely the characteristics of all geometrical propositions.

<a65> So the only remaining means is the first, namely to attain such knowledge through pure concepts or through apriori intuitions. However, it is clear that no synthetic knowledge can be obtained from pure concepts, but only analytic knowledge. [B65] Just take the proposition ‘With two straight lines it is impossible to enclose a space and hence to construct a figure,’ and try to derive it from the concepts of straight lines and of the number two. Again, take the proposition ‘It is possible to construct a figure out of three straight lines,’ and try to derive it simply from these concepts. All your efforts are in vain, and you find yourself forced to have recourse to intuition, as geometricians always do.

<a66> So an object has been given to you in intuition. But what sort of intuition is this? Is it a pure apriori intuition, or an empirical one? If it were an empirical one, it could never give rise to a universally valid proposition, let alone one known with demonstrative certainty; for experience can never provide anything of this sort.

<a67> You must therefore give yourself an object apriori in intuition, and base your synthetic proposition on it. Suppose the following were the case:

• you do not have within you a faculty for apriori intuition;
• these subjective preconditions, with respect to their form, are not at the same time the universal apriori preconditions for the possibility of the object itself of this outer intuition;
• the object (the triangle) is something in itself, without any relation to you as subject.

On these suppositions, how could you say that what is included among the subjective preconditions necessary for you to construct 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) which must necessarily be found for that purpose in the object, since [B66] the object is given before your experience, and not through it.

<a68> So space (and time as well) is a mere form of intuition, which contains the apriori preconditions for things to be outer objects for you, and these objects are in themselves nothing without these subjective preconditions. If this were not the case, you would not be able to decide anything at all about outer objects that was both synthetic and apriori. Therefore it is indubitably certain, and not merely possible or probable, that space and time are merely the subjective preconditions of all our intuition, since they are the necessary preconditions of all outer and inner experience. Consequently, in relation to these preconditions, all objects are mere appearances, and since they are given in this way, they are not things existing by themselves. This is why we can say many things about them apriori, at least as far as their form is concerned; whereas we can never say anything at all about the thing in itself that might underlie these appearances.

<a69> Note 2

The following note will serve admirably to confirm my theory of the ideality of both the outer and the inner senses, and hence the ideality of the objects of the senses, as mere appearances. Let us consider everything in our knowledge which belongs to intuition — so this immediately excludes the feelings of desire or aversion, and the will, since they are not kinds of knowledge. Now everything which belongs to intuition contains nothing but mere relations: relations of places in one intuition (extension), [B67] change of places (motion), and laws in accordance with which this change is determined (motive forces). But these relations do not tell us what is present in the place, or what brings about change of place in things themselves. A thing is not known as it is in itself merely through relations. So it is easy to judge that, since only representations of relations are given to us through outer sense, this sense can contain in its representation only the relation of an object to the subject, and not the inner properties of the object in itself.

<a70> Exactly the same is true of inner intuition. This is partly because it is in inner intuition that the representations of the outer senses constitute the essential material with which we occupy our minds. But it is also because inner intuition contains the time in which we place these representations, and which itself precedes consciousness of them in experience. Time underlies these representations as the formal precondition of the way in which we place them in our minds, and it already includes the relations of succession and simultaneity, and of that which is simultaneous with succession, namely the persistent.

<a71> Now that which, as representation, can precede any act of thinking something, is intuition; and if it contains nothing other than relations, it is the form of intuition. Since this form does not represent anything unless something is placed in the mind, it cannot be anything other than the way in which the mind is affected through its own activity (namely this [B68] placing of its representation), and hence it is the way in which the mind is affected by itself. In other words, it is an inner sense as far as its form is concerned.

<a72> Everything that is represented through a sense is to that extent always an appearance. In the case of inner sense, we must either deny the existence of such a sense altogether, or accept that the self as subject (which is the object of inner sense) can be represented through it only as an appearance. This is quite different from how the subject would judge itself to be, if its intuition were pure self-activity, that is to say, intellectual.

<a73> The only remaining difficulty is that of how a subject can intuit itself inwardly — but this difficulty is common to all theories. Consciousness of oneself (apperception) is a simple representation of the ‘I’; and if through this alone all the multiplicity within the subject were given through the activity of the self, then the inner intuition would be intellectual. But in humans, this consciousness requires inner perception of the multiplicity already given in the subject, and the means by which this is given in the mind without spontaneity must be called sensibility, in order to keep it distinct from intellectual intuition.

<a74> If the faculty of self-consciousness is to apprehend what lies in the soul, it must affect the soul. This is the only way it can stimulate an intuition of itself. But the form of the intuition, which already underlies it in the mind, determines the way in which the multiplicity is connected together in the mind, and it does this through the representation [B69] of time. So the mind intuits itself, not as it would represent itself if it were directly self-active, but as it is inwardly affected. Consequently, it intuits itself as it appears to itself, and not as it is.

<a75> Note 3

I have said that the intuition of outer objects and the self-intuition of the mind both represent objects and the mind in space and time as they affect our senses — in other words, as they appear. But I do not mean by this that these objects are a mere illusion. For in appearance, objects, and even the properties we attribute to them, are always regarded as something actually given. All I mean is that, if we take into account the relation between the given object and the subject, then these properties depend only on the way the subject intuits them. Consequently, the object as appearance will be distinct from the same object as it is in itself.

<a76> I have also said that the essential nature of space and time, in which I locate bodies and the soul as a precondition for their existence, is to be found in my way of intuiting them, and not in objects as they are in themselves. But again, I do not mean that bodies merely seem to be outside me, or that my soul merely seems to be given in my self-consciousness. It would be my own fault if I turned what I should count as appearance into mere illusion.*

<a78> This [B70] confusion between appearance and mere illusion as not a consequence of my principle of the ideality of all our sensory intuitions. Rather, it is a consequence of attributing objective reality to these forms of representation, which makes it impossible to avoid turning everything into mere illusion. Just suppose that space and time are properties which must be found in things in themselves if they are to be possible. Then consider the absurdities this would involve us in. There would be two infinite things, which are neither substances nor anything actual inhering in substances — yet they would have to be something existent, [B71] and even be the necessary precondition for the existence of all things. Still worse, they would continue to exist, even if all existing things were annihilated. On this showing, we can hardly blame the good Berkeley for demoting bodies to mere illusion. Indeed, the same would have to be true even of our own existence. If it were similarly made dependent on the self-subsistent reality of a non-thing such as time, it would be reduced to sheer illusion along with time. But no-one has yet allowed themselves to be guilty of such an absurdity.

<a79> Note 4

I now turn to natural theology. Here, we think an object which not only cannot be an object of intuition for us, but which also can in no way be an object of sensory intuition for himself. We are therefore careful to remove the preconditions of space and time from all his intuition — and all his knowledge must consist of intuition rather than thought, since thought always involves limitations. But by what right do we remove these preconditions, if we have already made both of them forms of things in themselves? As such, they would remain apriori preconditions for the existence of things, even if the things themselves did not exist. Therefore, as preconditions for all existence in general, they would also have to be preconditions for the existence of God.

<a80> But if we do not want to make space and time objective forms [B72] which apply to all things, the only alternative is to make them the subjective forms of both our outer and our inner ways of intuiting things. This way of intuiting things is called ‘sensory’, because it is not originative — that is, it is not such that through it alone the existence of the object of intuition is given. As far as we are aware, only God has originative intuition. Our way of intuiting things depends on the existence of the object; so it is possible only if the faculty of representation in the subject is affected by the object.

<a81> It is not necessarily the case that humans are the only beings whose sensibility is restricted to intuitions in space and time. It might be that every finite thinking being must necessarily share this feature with humans — though we are not in a position to judge whether this is so or not. But however universal it might be, it would not cease to be sensibility, precisely because it is a derivative, and not an originative intuition, and hence not an intellectual one. For reasons I have already given, intellectual intuition seems to belong only to God, and it should never be attributed to a dependent being, which is dependent both as to its existence and as to its intuition (which determines its existence in relation to the objects given to it). However, this last remark must be taken merely as a clarification of my theory of the Aesthetic, and not as part of its proof.

<a82> [B73] Conclusion of the Transcendental Aesthetic

Here we now have one of the elements required for the solution of the general problem of transcendental philosophy, namely: how are synthetic apriori propositions possible? This element consists in the pure apriori intuitions of space and time. When we wish to make an apriori judgment which goes beyond the concept given, it is space and time that contain what can be discovered apriori, and connected synthetically with the concept. It is not in the concept, but in the intuition which corresponds to the concept. But for this reason, such a judgment cannot extend beyond objects of the senses, and can be valid only for objects of possible experience.

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