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Kant

The Critique of Pure Reason 

 Transcendental Aesthetic: A

return to 'critique of pure reason' contents page 

Immanuel Kant (1724-1804)

auxiliary sources for 'The Critique'

VG: Professor Victor Gijsbers, Netherlands, youtube lectures

DR: Professor Daniel Robinson, Oxford, youtube lectures

RPW: Prof. Robert Paul Wolff, youtube lectures

MJ: translation, Mieklejohn

PG: translation, Paul Guyer

MM: translation, Max Muller: "[His] main merit, as he has very justly claimed, is his greater accuracy in rendering passages in which a specially exact appreciation of the niceties of German idiom happens to be important for the sense." TN

TN: translation, N.K. Smith

PR: translation-commentary, P.M. Rudisill

CN: commentary, N.K. Smith

SG: commentary, Sebastian Gardner

SP: glossary, Stephen Palmquist

LT: glossary, Lucas Thorpe

 *********************************************

In whatever way and through whatever means a cognition may relate
to objects, that through which it relates immediately to them, and at
which all thought as a means is directed as an end, is intuition. This,
however, takes place only insofar as the object is given to us; but this in
turn, is possible only if it affects the mind in a certain way. The capac
ity (receptivity) to acquire representations through the way in which
we are affected by objects is called sensibility. Objects are therefore
given to us by means of sensibility, and it alone affords us intuitions;
but they are thought through the understanding, and from it arise
concepts. But all thought, whether straightaway (direct) or through a
detour (indirect), must ultimately be related to intuitions, thus, in our
case, to sensibility, since there is no other way in which objects can be
given to us.
 

The effect of an object on the capacity for representation, insofar as we are affected by it, is sensation. That intuition which is related to the object through sensation is called empirical. The undetermined object
of an empirical intuition is called appearance.

I call that in the appearance which corresponds to sensation its matter,
but that which allows the manifold of appearance to be intuited as or-

dered in certain relations I call the fonn of appearance. Since that within
which the sensations can alone be ordered and placed in a certain form
cannot itself be in turn sensation, the matter of all appearance is only
given to us a posteriori, but its form must all lie ready for it in the mind a
priori, and can therefore be considered separately from all sensation.
I call all representations pure (in the transcendental sense) in which
nothing is to be encountered that belongs to sensation. Accordingly the
pure form of sensible intuitions in general is to be encountered in the
mind a priori, wherein all of the manifold of appearances is intuited in
certain relations. This pure form of sensibility itself is also called pure
intuition. So if I separate from the representation of a body that which
the understanding thinks about it, such as substance, force, divisibility,
etc., as well as that which belongs to sensation, such as impenetrability,
hardness, color, etc., something from this empirical intuition is still left
for me, namely extension and form. These belong to the pure intuition,
which occurs a priori, even without an actual object of the senses or sen
sation, as a mere form of sensibility in the mind.

I call a science of all principles of a priori sensibility the transcen
dental aesthetic. There must therefore be such a science, which
constitutes the first part of the transcendental doctrine of elements, in
contrast to that which contains the principlesc of pure thinking, and is
named transcendental logic.

In the transcendental aesthetic we will therefore first isolate sensibility by separating off everything that the understanding thinks through
its concepts, so that nothing but empirical intuition remains. Second,
we will then detach from the latter everything that belongs to sensation,
so that nothing remains except pure intuition and the mere form of ap
pearances, which is the only thing that sensibility can make available a
priori. In this investigation it will be found that there are two pure forms
of sensible intuition as principlesa of a priori cognition, namely space
and time, with the assessment of which we will now be concerned.
 

By means of outer sense (a property of our mind) we represent to our
selves objects as outside us, and all as in space. In space their form,
magnitude, and relation to one another is determined, or deter
minable, inner sense, by means of which the mind intuits itself, or its
inner state, gives, to be sure, no intuition of the soul itself, as an ob-
ject; yet it is still a determinate form, under which the intuition of its
inner state is alone possible, so that everything that belongs to the
inner determinations is represented in relations of time. Time can no
more be intuited externally than space can be intuited as something in
us.

Now what are space and time? Are they actual entities? Are they
only determinations or relations of things, yet ones that would pertain
to them even if they were not intuited, or are they relations that only
attach to the form of intuition alone, and thus to the subjective consti-tution of our mind, without which these predicates could not be as
cribed to anything at all? In order to instruct ourselves about this, we
will consider space first.

1) Space is not an empirical concept that has been drawn from outer
experiences. For in order for certain sensations to be relatedd to some
thing outside me (i.e., to something in another place in space from that
in which I find myself), thus in order for me to represent them as out
side one another, thus not merely as different but as in different places,
the representation of space must already be their ground) Thus the
representation of space cannot be obtained from the relations of outer appearance through experience, but this outer experience is itself first
possible only through this representation.
 

2) Space is a necessary representation, a priori, which is the ground of
all outer intuitions. One can never represent that there is no space, al
though one can very well think that there are no objects to be encoun
tered in it. It is therefore to be regarded as the condition of the possi
bility of appearances, not as a determination dependent on them, and is
an a priori representation that necessarily grounds outer appearances.

3) The apodictic certainty of all geometrical principles and the possi
bility of their a priori construction are grounded in this a priori necessity.
For if this representation of space were a concept acquired a posteriori,
which was drawn out of general outer experience, the first principles of
mathematical determination would be nothing but perceptions. They
would therefore have all the contingency of perception, and it would not
even be necessary that only one straight line lie between two points, but
experience would merely always teach that. What is borrowed from ex
perience always has only comparative universality, namely through in
duction. One would therefore only be able to say that as far as has been
observed to date, no space has been found that has more than three
dimensions.

4) Space is not a discursive or, as is said, general concept of relations of things in general, but a pure intuition. For, first, one can only repre
sent a single space, and if one speaks of many spaces, one understands by that only parts of one and the same unique space. And these parts cannot as it were precede the single all-encompassing space as its components (from which its composition would be possible), but rather are only thought in it. It is essentially single; the manifold in it, thus also the general concept of spaces in general, rests merely on limitations.
 

From this it follows that in respect to it an a priori intuition (which is
not empirical) grounds all concepts of them. Thus also all geometrical
principles, e.g., that in a triangle two sides together are always greater
than the third, are never derived from general concepts of line and tri
angle, but rather are derived from intuition and indeed derived a priori
with apodictic certainty.
 

5) Space is represented as a given infinite magnitude. A general con
cept of space (which is common to a foot as well as an ell) can determine nothing in respect to magnitude. If there were not boundlessness in the progress of intuition, no concept of relations could bring with it a principle of their infinity.

Conclusions from the above concepts.
 

a) Space represents no property at all of any things in themselves nor
any relation of them to each other, i.e., no determination of them that
attaches to objects themselves and that would remain even if one were
to abstract from all subjective conditions of intuition. For neither a
solute nor relative determinations can be intuited prior to the existence
of the things to which they pertain, thus be intuited a priori.
 

b) Space is nothing other than merely the form of all appearances of
outer sense, i.e., the subjective condition of sensibility, under which
alone outer intuition is possible for us. Now since the receptivity of the
subject to be affected by objects necessarily precedes all intuitions of
these objects, it can be understood how the form of all appearances can
be given in the mind prior to all actual perceptions, thus 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.
 

We can accordingly speak of space, extended beings, and so on, only
from the human standpoint. If we depart from the subjective condition
under which alone we can acquire outer intuition, namely that through
which we may be affected by objects, then the representation of space

signifies nothing at all. This predicate is attributed to things only inso
far as they appear to us, i.e., are objects of sensibility. The constant
form of this receptivity, which we call sensibility, is a necessary condi
tion of all the relations within which objects can be intuited as outside
us, and, if one abstracts from these objects, it is a pure intuition, which
bears 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 well say that space comprehends all things that
may appear to us externally, but not all things in themselves, whether
they be intuited or not, ord by whatever subject they may be intuited.
For we cannot judge at all whether the intuitions of other thinking be
ings are bound to the same conditions that limit our intuition and that
are universally valid for us. If we add the limitation of a judgment to the
concept of the subject, then the judgment is unconditionally valid. The
proposition "All things are next to one another in space" is valid only
under the limitation that these things be taken as objects of our sensible
intuition. If here I add the condition to the concept and say: "All things,
as outer intuitions, are next to one another in space," then this rule is
valid universally and without limitation. Our expositions accordingly
teach the reality (i.e., objective validity) of space in regard to everything
that can come before us externally as an object, but at the same time the
ideality of space in regard to things when they are considered in them
selves through reason, i.e., without taking account of the constitution of
our sensibility. We therefore assert the empirical reality of space (with
respect to all possible outer experience), though to be sure at the same
time its transcendental ideality, i.e., that it is nothing as soon as we
leave out the condition of the possibility of all experience, and take it as
something that grounds the things in themselves.

Besides space, however, there is no other subjective representation
related to something external that could be called a priori objective.
Hence this subjective condition of all outer appearances cannot be
compared with any other. The pleasant taste of a wine does not belong
to the objective determinations of the wine, thus of an object even con
sidered as an appearance, but rather to the particular constitution of
sense in the subject that enjoys it. Colors are not objective qualities of
the bodies to the intuition of which they are attached, but are also only
modifications of the sense of sight, which is affected by light in a cer
tain way. Space, on the contrary, as a condition of outer objects neces
sarily belongs to their appearance or intuition. Taste and colors are by
no means necessary conditions under which alone the objects can be objects of the senses for us. They are only combined with the appear-
ance as contingently added effects of the particular organization. Hence
they are not a priori representations, but are grounded on sensation, and
pleasant taste is even grounded on feeling (of pleasure and displeasure)
as an effect of the sensation. And no one can have a priori the represen-
tation either of a color or of any taste: but space concerns only the pure
form of intuition, thus it includes no sensation (nothing empirical) in it-
self, and all kinds and determinations of space can and even must be
able to be represented a priori if concepts of shapes as well as relations
are to arise. Through space alone is it possible for things to be outer obects for us.
 

The aim of this remark is only to prevent one from thinking of illustrating the asserted ideality of space with completely inadequate examples, since things like colors, taste, etc., are correctly considered not as
qualities of things but as mere alterations of our subject, which can even
be different in different people. For in this case that which is originally
itself only appearance, e.g., a rose, counts in an empirical sense as a
thing in itself, which yet can appear different to every eye in regard to color. The transcendental concept of appearances in space, on the con-
trary, is a critical reminder that absolutely nothing that is intuited in
space is a thing in itself, and that space is not a form that is proper to
anything in itself, but rather that objects in themselves are not known
to us at all, and that what we call outer objects are nothing other than
mere representations of our sensibility, whose form is space, but whose
true correlate, i.e., the thing in itself, is not and cannot be cognized
through them, but is also never asked after in experience.

The Transcendental Aesthetic
Second Section
On time.

Time is (1) not an empirical concept that is somehow drawn from an ex
perience. For simultaneity or succession would not themselves come
into perception if the representation of time did not ground them a priori. Only under its presupposition can one represent that several things
exist at one and the same time (simultaneously) or in different times
(successively).
 

Time is (2) a necessary representation that grounds all intuitions. In
regard to appearances in general one cannot remove time, though one
can very well take the appearances away from time. Time is therefore
given a priori. In it alone is all actuality of appearances possible. The lat
ter could all disappear, but time itself, as the universal condition of their
possibility, cannot be removed.
 

(3) This a priori necessity also grounds the possibility of apodictic
principles of the relations of time, or axioms of time in general. It has
only one dimension: different times are not simultaneous, but succes
sive (just as different spaces are not successive, but simultaneous).
These principles could not be drawn from experience, for this would
yield neither strict universality nor apodictic certainty. We would only
be able to say: This is what common perception teaches, but not: This
is how matters must stand. These principles are valid as rules under
which experiences are possible at all, and instruct us prior to them, not
through it.
 

(4) Time is no discursive or, as one calls it, general concept, but a pure form of sensible intuition. Different times are only parts of one and the
same time. That representation, however, which can only be given
through a single object, is an intuition. Further, the proposition that
different times cannot be simultaneous cannot be derived from a gen-

eral concept. The proposition is synthetic, and cannot arise from con
cepts alone. It is therefore immediately contained in the intuition and
representation of time.

(5) The infinitude of time signifies nothing more than that every de
terminate magnitude of time is only possible through limitations of a single time grounding it. The original representation, time, must there-
fore be given as unlimited. But where the parts themselves and every
magnitude of an object can be determinately represented only through
limitation, there the entire representation cannot be given through
concepts (for then the partial representations precede) but their imme-
diate intuition must be the ground.

Conclusions from these concepts.
 

a) Time is not something that would subsist for itself or attach to things
as an objective determination, and thus remain if one abstracted from
all subjective conditions of the intuition of them; for in the first case it
would be something that was actual yet without an actual object. As far
as the second case is concerned, however, time could not precede the objects as a determination or order attaching to the things themselves
as their condition and be cognized and intuited a priori through syn-
thetic propositions. But the latter, on the contrary, can very well occur
if time is nothing other than the subjective condition under which all
intuitions can take place in us. For then this form of inner intuition can
be represented prior to the objects, thus a priori.
 

b) Time is nothing other than the form of inner sense, i.e., of the in
tuition of our self and our inner state.'9 For time cannot be a determi
nation of outer appearances; it belongs neither to a shape or a position, etc., but on the contrary determines the relation of representations in
our inner state. And just because this inner intuition yields no shape we
also attempt to remedy this lack through analogies, and represent the
temporal sequence through a line progressing to infinity, in which the
manifold constitutes a series that is of only one dimension, and infer
from the properties of this line to all the properties of time, with the
sole difference that the parts of the former are simultaneous but those
of the latter always exist successively. From this it is also apparent that
the representation of time is itself an intuition, since 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 intuitions, is limited as an a priori
condition merely to outer intuitions. But since, on the contrary, all rep
resentations, whether or not they have outer things as their object, nev
ertheless as determinations of the mind themselves belong to the inner
state, while this inner state belongs under the formal condition of inner

intuition, and thus of time, so time is an a priori condition of all ap
pearance in general, and indeed the immediate condition of the inner
intuition (of our souls), and thereby also the mediate condition of outer
appearances. If I can say a priori: all outer appearances are in space and determined a priori according to the relations of space, so from the
principle of inner sense I can say entirely generally: all appearances in
general, i.e., all objects of the senses, are in time, and necessarily stand
in relations of time.

If we abstract from our way of internally intuiting ourselves and by
means of this intuition also dealing with all outer intuitions in the
power of representation, and thus take objects as they may be in them
selves, then time is nothing. It is only of objective validity in regard to
appearances, because these are already things that we take as objects of our senses; but it is no longer objective if one abstracts from the sen
sibility of our intuition, thus from that kind of representation that is pe
culiar to us, and speaks of things in general. Time is therefore merely
a subjective condition of our (human) intuition (which is always sensi
ble, i.e., insofar as we are affected by objects), and in itself, outside the
subject, is nothing. Nonetheless it is necessarily objective in regard to
all appearances, thus also in regard to all things that can come before us
in experience. We cannot say all things are in time, because with the
concept of things in general abstraction is made from every kind of in
tuition of them, but this is the real condition under which time belongs
to the representation of objects. Now if the condition is added to the
concept, and the principle says that all things as appearances (objects of
sensible intuition) are in time, then the principle has its sound objective
correctness and a priori universality.

Our assertions accordingly teach the empirical reality of time, i.e.,
objective validity in 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 would not belong under the condition of
time. But, on the contrary, we dispute all claim of time to absolute re
ality, namely where it would attach to things absolutely as a condition
or property even without regard to the form o f our sensible intuition.

Such properties, which pertain to things in themselves, can never be
given to us through the senses. In this therefore consists the transcen
dental ideality of time, according to which it is nothing at all if one ab
stracts from the subjective conditions of sensible intuition, and cannot
be counted as either subsisting or inhering in the objects in themselves
(without their relation to our intuition). Yet this ideality is to be compared with the subreptions of sensation just as little as that of space is,
because in that case one presupposes that the appearance itself, in which these predicates inhere, has objective reality, which is here entirely absent except insofar as it is merely empirical, i.e., the object itself is re
garded merely as appearance: concerning which the above remark in
the previous section is to be consulted.

Elucidation.

Against this theory, which concedes empirical reality to time but dis-
putes its absolute and transcendental reality, insightful men have so
unanimously proposed one objection that I conclude that it must natu-
rally occur to every reader who is not accustomed to these considera
tions. It goes thus: Alterations are real (this is proved by the change of our own representations, even if one would deny all outer appearances
together with their alterations). Now alterations are possible only in
time, therefore time is something real. There is no difficulty in answering. I admit the entire argument. Time is certainly something real namely the real form of inner intuition. It therefore has subjective reality in regard to inner experience, i.e., I really have the representation of time and of my determinations in it. It is therefore to be regarded really not as object but as the way of representing myself as object. But if I or another being could intuit myself without this condition of sensibility, then these very determinations, which we now represent to ourselves as alterations, would yield us a cognition in which the representation of time and thus also of alteration would not occur at all. Its empirical reality therefore remains as a condition of all our experiences.
 

Only absolute reality cannot be granted to it according to what has been
adduced above. It is nothing except the form of our inner intuition. *

* I can, to be sure, say: my representations succeed one another; but that only means that we are conscious of them as in a temporal sequence, i.e., according to the form of inner sense. Time is not on that account something in it self, nor any determination objectively adhering to things.
 

If one removes the special condition of our sensibility from it, then the
concept of time also disappears, and it does not adhere to the objects themselves, rather merely to the subject that intuits them.

The cause, however, on account of which this objection is so unani
mously made, and indeed by those who nevertheless know of nothing
convincing to object against the doctrine of the ideality of space is
this. They did not expect to be able to demonstrate the absolute reality
of space apodictically, since they were confronted by idealism, accord
ing to which the reality of outer objects is not capable of any strict proof;
on the contrary, the reality of the object of our inner sense (of myself
and my state) is immediately clear through consciousness. The former
could have been a mere illusion, but the latter, according to their opin
ion, is undeniably something real. But they did not consider that both,
without their reality as representations being disputed, nevertheless be
long only to appearance, which always has two sides, one where the ob
ject is considered in itself (without regard to the way in which it is to be
intuited, the constitution of which however must for that very reason al
ways remain problematic), the other where the form of the intuition of
this object is considered, which must not be sought in the object in it
self but in the subject to which it appears, but which nevertheless really
and necessarily pertains to the representation of this object.

Time and space are accordingly two sources of cognition, from which
different synthetic cognitions can be drawn a priori, of which especially
pure mathematics in regard to the cognitions of space and its relations
provides a splendid example. Both taken together are, namely, the
pure forms of all sensible intuition, and thereby make possible synthetic
a priori propositions. But these a priori sources of cognition determine
their own boundaries by that very fact (that they are merely conditions
of sensibility), namely that they apply to objects only so far as they are
considered as appearances, but do not present things in themselves.
Those alone are the field of their validity, beyond which no further obj ective use of them takes place. This reality of space and time, further,
leaves the certainty of experiential cognition untouched: for we are just
as certain of that whether these forms necessarily adhere to the things
in themselves or only to our intuition of these things. Those, however,
who assert the absolute reality of space and time, whether they assume
it to be subsisting or only inhering, must themselves come into conflict
with the principles of experience. For if they decide in favor of the first
(which is generally the position of the mathematical investigators of na
ture), then they must assume two eternal and infinite self-subsisting
non-entities (space and time), which exist (yet without there being any-thing real) only in order to comprehend everything real within them-
selves. If they adopt the second position (as do some metaphysicians of nature), and hold space and time to be relations of appearances (next to or successive to one another) that are abstracted from experience
though confusedly represented in this abstraction, then they must dis-
pute the validity or at least the apodictic certainty of a priori mathemat-
ical doctrines in regard to real things (e.g., in space), since this certainty
does not occur a posteriori, and on this view the a priori concepts of space and time are only creatures of the imagination, the origin of which must really be sought in experience, out of whose abstracted relations imag ination has made something that, to be sure, contains what is general in them, but that cannot occur without the restrictions that nature has attached to them;

The first succeed in opening the field of appearances
for mathematical assertions; however, they themselves become very
confused through precisely these conditions if the understanding would
go beyond this field. The second succeed, to be sure, with respect to the
latter, in that the representations of space and time do not stand in their
way if they would judge of objects not as appearances but merely in re-
lation to the understanding; but they can neither offer any ground for
the possibility of a priori mathematical cognitions (since they lack a true
and objectively valid a priori intuition), nor can they bring the proposi-
tions of experience into necessary accord with those assertions. On our theory of the true constitution of these two original forms of sensibility both difficulties are remedied.
 

Finally, that the transcendental aesthetic cannot contain more than
these two elements, namely space and time, is clear from the fact that
all other concepts belonging to sensibility, even that of motion, which
unites both elements, presuppose something empirical. For this pre
supposes the perception of something movable. In space considered in
itself there is nothing movable; hence the movable must be something
that is found in space only through experience, thus an empirical
datum. In the same way the transcendental aesthetic cannot count the
concept of alteration among its a priori data; for time itself does not
alter, but only something that is within time. For this there is required
the perception of some existence and the succession of its determina
tions, thus experience.

General remarks on the transcendental aesthetic.
 

It will first be necessary to explain as distinctly as possible our opinion in regard to the fundamental constitution of sensible cognition in
general, in order to preclude all misinterpretation of it.
 

We have therefore wanted to say that all our intuition is nothing but
the representation of appearance; that the things that we intuit are not
in themselves what we intuit them to be, nor are their relations so con
stituted in themselves as they appear to us; and that if we remove our
own subject or even only the subjective constitution of the senses in
general, then all the constitution, all relations of objectsa in space and
time, indeed space and time themselves would disappear, and as ap
pearances they cannot exist in themselves, but only in us. What may be
the case with objects in themselves and abstracted from all this recep
tivity of our sensibility remains entirely unknown to us. We are ac
quainted with nothing except our way of perceiving them, which is
peculiar to us, and which therefore does not necessarily pertain to every
being, though to be sure it pertains to every human being. We are con-
cerned solely with this. Space and time are its pure forms, sensation in
general its matter. We can cognize only the former a priori, i.e., prior to
all actual perception, and they are therefore called pure intuition; the
latter, however, is that in our cognition that is responsible for it being
called a posteriori cognition, i.e., empirical intuition. The former ad
heres to our sensibility absolutely necessarily, whatever sort of sensa-tions we may have; the latter can be very different. Even if we could
bring this intuition of ours to the highest degree of distinctness we
would not thereby come any closer to the constitution of objects in
themselves. For in any case we would still completely cognize only our
own way of intuiting, i.e., our sensibility, and this always only under the
conditions originally depending on the subject, space and time; what
the objects may be in themselves would still never be known through
the most enlightened cognition of their appearance, which is alone
given to us.

That our entire sensibility is nothing but the confused representation
of things, which contains solely that which pertains to them in them
selves but only under a heap of marks and partial representations that
we can never consciously separate from one another, is therefore a fal
sification of the concept of sensibility and of appearance that renders
the entire theory of them useless and empty. The difference between an
indistinct and a distinct representation is merely logical, and does not
concern the content. Without doubt the concept of right that is used by the healthy understanding contains the very same things that the
most subtle speculation can evolve out of it, only in common and prac-
tical use one is not conscious of these manifold representations in these
thoughts. Thus one cannot say that the common 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 constitution) of actions that pertains to them in themselves. The
representation of a body in intuition, on the contrary, contains nothing
at all that could pertain to an object in itself, but merely the appearance
of something and the way in which we are affected by it; and this re
ceptivity of our cognitive capacity is called sensibility and remains
worlds apart from the cognition of the object in itself even if one might
see through to the very bottom of it (the appearance).
 

The Leibnizian-Wolffian philosophy has therefore directed all inves
tigations of the nature and origin of our cognitions to an entirely unjust
point of view in considering the distinction between sensibility and the
intellectual as merely logical, since it is obviously transcendental, and
does not concern merely the form of distinctness or indistinctness, but its origin and content, so that through sensibility we do not cognize the
constitution of things in themselves merely indistinctly, but rather not at
all, and, as soon as we take away our subjective constitution, the repre
sented object with the properties that sensible intuition attributes to it
is nowhere to be encountered, nor can it be encountered, for it is just this
subjective constitution that determines its form as appearance.
 

We ordinarily distinguish quite well between that which is essentially
attached to the intuition of appearances, and is valid for every human
sense in general, and that which pertains to them only contingently be-
cause it is not valid for the relationb to sensibility in general but only for
a particular situation or organization of this or that sense. And thus one
calls the first cognition one that represents the object in itself, but the
second one only its appearance. This distinction, however, is only em
pirical. If one stands by it (as commonly happens) and does not regard
that empirical intuition as in turn mere appearance (as ought to hap-
pen), so that there is nothing to be encountered in it that pertains to any
thing in itself, then our transcendental distinction is lost, and we believe
ourselves to cognize things in themselves, although we have nothing to
do with anything except appearances anywhere (in the world of sense), even in the deepest research into its objects. Thus, we would certainly call a rainbow a mere appearance in a sun-shower, but would call this
rain the thing in itself, and this is correct, as long as we understand the
latter concept in a merely physical sense, as that which in universal ex
perience and all different positions relative to the senses is always de
termined thus and not otherwise in intuition. But if we consider this
empirical object in general and, without turning to its agreement with
every human sense, ask whether it (not the raindrops, since these, as ap
pearances, are already empirical objects) represents an object in itself,
then the question of the relation of the representation to the object is
transcendental, and not only these drops are mere appearances, but
even their round form, indeed even the space through which they fall
are nothing in themselves, but only mere modifications or foundationsb
of our sensible intuition; the transcendental object,c however, remains
unknown to us.

The second important concern of our transcendental aesthetic is that
it not merely earn some favor as a plausible hypothesis, but that it be as
certain and indubitable as can ever be demanded of a theory that is to
serve as an organon. In order to make this certainty fully convincing we
will choose a case in which its validity can become obvious.
 

Thus, if it were to be supposed that space and time are in themselves
objective and conditions of the possibility of things in themselves, then
it would be shown, first, that there is a large number of a priori apodic
tic and synthetic propositions about both, but especially about space,
which we will therefore here investigate as our primary example. Since
the propositions of geometry are cognized synthetically a priori and
with apodictic certainty, I ask: Whence do you take such propositions,
and on what does our understanding rely in attaining to such absolutely
necessary and universally valid truths? There is no other way than
through concepts or through intuitions, both of which, however, are
given, as such, either a priori or a posteriori. The latter, namely empiri
cal concepts, together with that on which they are grounded, empirical
intuition, cannot yield any synthetic proposition except one that is also
merely empirical, i.e., a proposition of experience; thus it can never
contain necessity and absolute universality of the sort that is neverthe
less characteristic of all propositions of geometry. Concerning the first
and only means for attaining to such cognitions, however, namely
through mere concepts or a priori intuitions, it is clear that from mere
concepts no synthetic cognition but only merely analytic cognition can
be attained. Take the proposition that with two straight lines no space at all can be enclosed, thus no figure is possible, and try to derive it from
the concept of straight lines and the number two; or take the proposi-
tion that a figure is possible with three straight lines, and in the same
way try to derive it from these concepts. All of your effort is in vain, and
you see yourself forced to take refuge in intuition, as indeed geometry
always does. You thus give yourself an object in intuition; but what kind is this, is it a pure a priori intuition or an empirical one? If it were the
latter, then no universally valid, let alone apodictic proposition could
ever come from it: for experience can never provide anything of this
sort. You must therefore give your object a priori in intuition, and
ground your synthetic proposition on this. If there did not lie in you a
faculty for intuiting a priori; if this subjective condition regarding 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:
then how could you say that what necessarily lies in your subjective con
ditions for constructing a triangle must also necessarily pertain to the
triangle in itself? for you could not add to your concept (of three lines)
something new (the figure) that must thereby necessarily be encoun-tered in the object, since this is given prior to your cognition and not
through it. If, therefore, space (and time as well) were not a mere form
of your intuition that contains a priori conditions under which alone
things could be outer objects for you, which are nothing in themselves
without these subjective conditions, then you could make out absolutely
nothing synthetic and a priori about outer objects. It is therefore in
dubitably 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 relationd to
which therefore all objects are mere appearances and not things given
for themselves in this way; about these appearances, further, much may
be said a priori that concerns their form, but nothing whatsoever about
the things in themselves that may ground them.