With the exception of space there is no other subjective representation (Vorstellung) referring to something external, that would be called a priori objective. [This3 subjective condition of all external phenomena cannot therefore be compared to any other. The taste of wine does not belong to the objective determinations of wine, considered as an object, even as a phenomenal object, but to the peculiar nature of the sense belonging to the subject that tastes the wine. Colours are not qualities of a body, though inherent in its intuition, but they are likewise modifications only of the sense of sight, as it is affected in different ways by light. Space, on the contrary, as the very condition of external objects, is essential to their appearance or intuition. Taste and colour are by no means necessary conditions under which alone things can become to us objects of sensuous perception. They are connected with their appearance, as accidentally added effects only of our peculiar organisation. They are not therefore representations a priori, but are dependent on sensation (Empfindung), nay taste even on an affection (Gefühl) of pleasure and pain, which is the result of a sensation. No one can have a priori, an idea (Vorstellung) either of colour or of taste, but space refers to the pure form of intuition only, and involves no kind of sensation, nothing empirical; nay all kinds and determinations of space can and must be represented a priori, if concepts of forms and their relations are to arise. Through it alone is it possible that things should become external objects to us.]
My object in what I have said just now is only to prevent people from imagining that they can elucidate the ideality of space by illustrations which are altogether insufficient, such as colour, taste, etc., which should never be considered as qualities of things, but as modifications of the subject, and which therefore may be different with different people. For in this case that which originally is itself a phenomenon only, as for instance, a rose, is taken by the empirical understanding for a thing by itself, which nevertheless, with regard to colour, may appear different to every eye. The transcendental conception, on the contrary, of all phenomena in space, is a critical warning that nothing which is seen in space is a thing by itself, nor space a form of things supposed to belong to them by themselves, but that objects by themselves are not known to us at all, and that what we call external objects are nothing but representations of our senses, the form of which is space, and the true correlative of which, that is the thing by itself, is not known, nor can be known by these representations, nor do we care to know anything about it in our daily experience.
Second Section Of The Transcendental Æsthetic4
Of Time
I. Time is not an empirical concept deduced from any experience, for neither coexistence nor succession would enter into our perception, if the representation of time were not given a priori. Only when this representation a priori is given, can we imagine that certain things happen at the same time (simultaneously) or at different times (successively).
II. Time is a necessary representation on which all intuitions depend. We cannot take away time from phenomena in general, though we can well take away phenomena out of time. Time therefore is given a priori. In time alone is reality of phenomena possible. All phenomena may vanish, but time itself (as the general condition of their possibility) cannot be done away with.
III. On this a priori necessity depends also the possibility of apodictic principles of the relations of time, or of axioms of time in general. Time has one dimension only; different times are not simultaneous, but successive, while different spaces are never successive, but simultaneous. Such principles cannot be derived from experience, because experience could not impart to them absolute universality nor apodictic certainty. We should only be able to say that common experience teaches us that it is so, but not that it must be so. These principles are valid as rules under which alone experience is possible; they teach us before experience, not by means of experience.5
IV. Time is not a discursive, or what is called a general concept, but a pure form of sensuous intuition. Different times are parts only of one and the same time. Representation, which can be produced by a single object only, is called an intuition. The proposition that different times cannot exist at the same time cannot be deduced from any general concept. Such a proposition is synthetical, and cannot be deduced from concepts only. It is contained immediately in the intuition and representation of time.
V. To say that time is infinite means no more than that every definite quantity of time is possible only by limitations of one time which forms the foundation of all times. The original representation of time must therefore be given as unlimited. But when the parts themselves and every quantity of an object can be represented as determined by limitation only, the whole representation cannot be given by concepts (for in that case the partial representations come first), but it must be founded on immediate intuition.6
Conclusions from the foregoing concepts
a. Time is not something existing by itself, or inherent in things as an objective determination of them, something therefore that might remain when abstraction is made of all subjective conditions of intuition. For in the former case it would be something real, without being a real object. In the latter it could not, as a deter-mination or order inherent in things themselves, be antecedent to things as their condition, and be known and perceived by means of synthetical propositions a priori. All this is perfectly possible if time is nothing but a subjective condition under which alone7 intuitions take place within us. For in that case this form of internal intuition can be represented prior to the objects themselves, that is, a priori.
b. Time is nothing but the form of the internal sense, that is, of our intuition of ourselves, and of our internal state. Time cannot be a determination peculiar to external phenomena. It refers neither to their shape, nor their position, etc., it only determines the relation of representations in our internal state. And exactly because this internal intuition supplies no shape, we try to make good this deficiency by means of analogies, and represent to ourselves the succession of time by a line progressing to infinity, in which the manifold constitutes a series of one dimension only; and we conclude from the properties of this line as to all the properties of time, with one exception, i.e. that the parts of the former are simultaneous, those of the latter successive. From this it becomes clear also, that the representation of time is itself an intuition, because all its relations can be expressed by means of an external intuition.
c. Time is the formal condition, a priori, of all phenomena whatsoever. Space, as the pure form of all external intuition, is a condition, a priori, of external phenomena only. But, as all representations, whether they have for their objects external things or not, belong by themselves, as determinations of the mind, to our inner state, and as this inner state falls under the formal conditions of internal intuition, and therefore of time, time is a condition, a priori, of all phenomena whatsoever, and is so directly as a condition of internal phenomena (of our mind) and thereby indirectly of external phenomena also. If I am able to say, a priori, that all external phenomena are in space, and are determined, a priori, according to the relations of space, I can, according to the principle of the internal sense, make the general assertion that all phenomena, that is, all objects of the senses, are in time, and stand necessarily in relations of time.
If we drop our manner of looking at ourselves internally, and of comprehending by means of that intuition all external intuitions also within our power of representation, and thus take objects as they may be by themselves, then time is nothing. Time has objective validity with reference to phenomena only, because these are themselves things which we accept as objects of our senses; but time is no longer objective, if we remove the sensuous character of our intuitions, that is to say, that mode of representation which is peculiar to ourselves, and speak of things in general. Time is therefore simply a subjective condition of our (human) intuition (which is always sensuous, that is so far as we are affected by objects), but by itself, apart from the subject
, nothing. Nevertheless, with respect to all phenomena, that is, all things which can come within our experience, time is necessarily objective. We cannot say that all things are in time, because, if we speak of things in general, nothing is said about the manner of intuition, which is the real condition under which time enters into our representation of things. If therefore this condition is added to the concept, and if we say that all things as phenomena (as objects of sensuous intuition) are in time, then such a proposition has its full objective validity and a priori universality.
What we insist on therefore is the empirical reality of time, that is, its objective validity, with reference to all objects which can ever come before our senses. And as our intuition must at all times be sensuous, no object can ever fall under our experience that does not come under the conditions of time. What we deny is, that time has any claim on absolute reality, so that, without taking into account the form of our sensuous condition, it should by itself be a condition or quality inherent in things; for such qualities which belong to things by themselves can never be given to us through the senses. This is what constitutes the transcendental ideality of time, so that, if we take no account of the subjective conditions of our sensuous intuitions, time is nothing, and cannot be added to the objects by themselves (without their relation to our intuition) whether as subsisting or inherent. This ideality of time, however, as well as that of space, should not be confounded with the deceptions of our sensations, because in their case we always suppose that the phenomenon to which such predicates belong has objective reality, which is not at all the case here, except so far as this objective reality is purely empirical, that is, so far as the object itself is looked upon as a mere phenomenon. On this subject see a previous note, in section i, on Space.
Explanation
Against this theory which claims empirical, but denies absolute and transcendental reality to time, even intelligent men have protested so unanimously, that I suppose that every reader who is unaccustomed to these considerations may naturally be of the same opinion. What they object to is this: Changes, they say, are real (this is proved by the change of our own representations, even if all external phenomena and their changes be denied). Changes, however, are possible in time only, and therefore time must be something real. The answer is easy enough. I grant the whole argument. Time certainly is something real, namely, the real form of our internal intuition. Time therefore has subjective reality with regard to internal experience: that is, I really have the representation of time and of my determinations in it. Time therefore is to be considered as real, not so far as it is an object, but so far as it is the representation of myself as an object. If either I myself or any other being could see me without this condition of sensibility, then these self-same determinations which we now represent to ourselves as changes, would give us a kind of knowledge in which the representation of time, and therefore of change also, would have no place. There remains therefore the empirical reality of time only, as the condition of all our experience, while absolute reality cannot, according to what has just been shown, be conceded to it. Time is nothing but the form of our own internal intuition.8 Take away the peculiar condition of our sensibility, and the idea of time vanishes, because it is not inherent in the objects, but in the subject only that perceives them.
The reason why this objection is raised so unanimously, and even by those who have nothing very tangible to say against the doctrine of the ideality of space, is this. They could never hope to prove apodictically the absolute reality of space, because they are confronted by idealism, which has shown that the reality of external objects does not admit of strict proof, while the reality of the object of our internal perceptions (the perception of my own self and of my own status) is clear immediately through our consciousness. The former might be merely phenomenal, but the latter, according to their opinion, is undeniably something real. They did not see that both, without denying to them their reality as representations, belong nevertheless to the phenomenon only, which must always have two sides, the one when the object is considered by itself (without regard to the manner in which it is perceived, its quality therefore remaining always problematical), the other, when the form of the perception of the object is taken into consideration; this form belonging not to the object in itself, but to the subject which perceives it, though nevertheless belonging really and necessarily to the object as a phenomenon.
Time and space are therefore two sources of knowledge from which various a priori synthetical cognitions can be derived. Of this pure mathematics give a splendid example in the case of our cognitions of space and its various relations. As they are both pure forms of sensuous intuition, they render synthetical propositions a priori possible. But these sources of knowledge a priori (being conditions of our sensibility only) fix their own limits, in that they can refer to objects only in so far as they are considered as phenomena, but cannot represent things as they are by themselves. That is the only field in which they are valid; beyond it they admit of no objective application. This ideality of space and time, however, leaves the truthfulness of our experience quite untouched, because we are equally sure of it, whether these forms are inherent in things by themselves, or by necessity in our intuition of them only. Those, on the contrary, who maintain the absolute reality of space and time, whether as subsisting or only as inherent, must come into conflict with the principles of experience itself. For if they admit space and time as subsisting (which is generally the view of mathematical students of nature) they have to admit two eternal infinite and self-subsisting nonentities (space and time), which exist without their being anything real, only in order to comprehend all that is real. If they take the second view (held by some metaphysical students of nature), and look upon space and time as relations of phenomena, simultaneous or successive, abstracted from experience, though represented confusedly in their abstracted form, they are obliged to deny to mathematical propositions a priori their validity with regard to real things (for instance in space), or at all events their apodictic certainty, which cannot take place a posteriori, while the a priori conceptions of space and time are, according to their opinion, creations of our imagination only. Their source, they hold, must really be looked for in experience, imagination framing out of the relations abstracted from experience something which contains the general character of these relations, but which cannot exist without the restrictions which nature has imposed on them. The former gain so much that they keep at least the sphere of phenomena free for mathematical propositions; but, as soon as the understanding endeavours to transcend that sphere, they become bewildered by these very conditions. The latter have this advantage that they are not bewildered by the representations of space and time when they wish to form judgments of objects, not as phenomena, but only as considered by the understanding; but they can neither account for the possibility of mathematical knowledge a priori (there being, according to them, no true and objectively valid intuition a priori), nor can they bring the laws of experience into true harmony with the a priori doctrines of mathematics. According to our theory of the true character of these original forms of sensibility, both difficulties vanish.
Lastly, that transcendental æsthetic cannot contain more than these two elements, namely, space and time, becomes clear from the fact that all other concepts belonging to the senses, even that of motion, which combines both, presuppose something empirical. Motion presupposes the perception of something moving. In space, however, considered by itself, there is nothing that moves. Hence that which moves must be something which, as in space, can be given by experience only, therefore an empirical datum. On the same ground, transcendental æsthetic cannot count the concept of change among its a priori data, because time itself does not change, but only something which is in time. For this, the perception of something existing and of the succession of its determinations, in other words, experience, is required.
General Observations On Transcendental Æsthetic
In order t
o avoid all misapprehensions it will be necessary, first of all, to declare, as clearly as possible, what is our view with regard to the fundamental nature of sensuous knowledge.
What we meant to say was this, that all our intuition is nothing but the representation of phenomena; that things which we see are not by themselves what we see, nor their relations by themselves such as they appear to us, so that, if we drop our subject or the subjective form of our senses, all qualities, all relations of objects in space and time, nay space and time themselves, would vanish. They cannot, as phenomena, exist by themselves, but in us only. It remains completely unknown to us what objects may be by themselves and apart from the receptivity of our senses. We know nothing but our manner of perceiving them, that manner being peculiar to us, and not necessarily shared in by every being, though, no doubt, by every human being. This is what alone concerns us. Space and time are pure forms of our intuition, while sensation forms its matter. What we can know a priori—before all real intuition, are the forms of space and time, which are therefore called pure intuition, while sensation is that which causes our knowledge to be called a posteriori knowledge, i.e. empirical intuition. Whatever our sensation may be, these forms are necessarily inherent in it, while sensations themselves may be of the most different character. Even if we could impart the highest degree of clearness to our intuition, we should not come one step nearer to the nature of objects by themselves. We should know our mode of intuition, i.e. our sensibility, more completely, but always under the indefeasible conditions of space and time. What the objects are by themselves would never become known to us, even through the clearest knowledge of that which alone is given us, the phenomenon.
It would vitiate the concept of sensibility and phenomena, and render our whole doctrine useless and empty, if we were to accept the view (of Leibniz and Wolf), that our whole sensibility is really but a confused representation of things, simply containing what belongs to them by themselves, though smothered under an accumulation of signs (Merkmal) and partial concepts, which we do not consciously disentangle. The distinction between confused and well-ordered representation is logical only, and does not touch the contents of our knowledge. Thus the concept of Right, as employed by people of common sense, contains neither more nor less than the subtlest speculation can draw out of it, only that in the ordinary practical use of the word we are not always conscious of the manifold ideas contained in that thought. But no one would say therefore that the ordinary concept of Right was sensuous, containing a mere phenomenon; for Right can never become a phenomenon, being a concept of the understanding, and representing a moral quality belonging to actions by themselves. The representation of a Body, on the contrary, contains nothing in intuition that could belong to an object by itself, but is merely the phenomenal appearance of something, and the manner in which we are affected by it. This receptivity of our knowledge is called sensibility. Even if we could see to the very bottom of a phenomenon, it would remain for ever altogether different from the knowledge of the thing by itself.
Critique of Pure Reason Page 9