changes under his hands into another, that of proving the existence of
external phenomena. "That external objects are real as representations"
Berkeley had never disputed.]
On the basis of the inseparability of sensibility and understanding the
ideal of knowledge--an extension of knowledge to be attained by _a priori_
means (p. 333)--experiences a remarkable addition in the position that the
rational synthesis thus obtained must be a knowledge of reality, must be
applied to matter given in intuition. To the question,
"How are synthetic
judgments _a priori possible_?" is joined a second equally legitimate
inquiry, "How do they become _objectively valid_, or applicable to objects
of experience?" The principle from which their validity is proved--they are
applicable to objects of experience because _without them experience would
not be possible_, because they are _conditions of experience_--like the
criterion of apriority (strict universality and necessity), is one of the
noëtic assumptions of the critical theory.[1]
[Footnote 1: Cf. Vaihinger, _Kommentar_, i. pp. 425-430.]
Inasmuch as its investigation relates to the conditions of experience the
Kantian criticism follows a method which it itself terms _transcendental_.
Heretofore, when the metaphysical method had been adopted, the object had
been the suprasensible; and when knowledge had been made the object of
investigation, the method followed had been empirical, psychological. Kant
had the right to consider himself the creator of noëtics, for he showed it
the transcendental point of view. Knowledge is an object of experience, but
its conditions are not. The object is to explain knowledge, not merely to
describe it psychologically,--to establish a new science of knowledge from
principles, from pure reason. That which lies beyond experience is
sealed from our thought; that which lies on this side of it is still
uninvestigated, though capable and worthy of investigation, and in
extreme need thereof. Criticism forbids the _transcendent_ use of reason
(transcending experience); it permits, demands, and itself exercises the
_transcendental_[1] use of it, which explains an experiential object,
knowledge, from its conditions, which are not empirically given.
[Footnote A: Kant applies the term _transcendental_ to the knowledge (the
discovery, the proof) of the _a priori_ factor and its relation to objects
of experience. Unfortunately he often uses the same word not only to
designate the _a priori_ element itself, but also as a synonym for
transcendent. In all three cases its opposite is _empirical_, namely,
empirico-psychological investigation by observation in distinction from
noëtical investigation from principles; empirical origin in distinction
from an origin in pure reason, and empirical use in distinction from
application beyond the limits of experience.]
There is, apparently, a contradiction between the empiristic result of the
Critique of Reason (the limitation of knowledge to objects of experience)
and its rationalistic proofs (which proceed metaphysically, not
empirically), and, in fact, a considerable degree of opposition really
exists. Kant argues in a metaphysical way that there can be no metaphysics.
This contradiction is solved by the distinction which has been mentioned
between that which is beyond, and that which lies within, the boundary of
experience. That metaphysic is forbidden which on the objective side soars
beyond experience, but that pure rational knowledge is permissible and
necessary which develops from principles the grounds of experiential
knowledge existing in the subject. In the Kantian school, however, these
complementary elements,--empirical result, transcendental or metaphysical,
properly speaking, pro-physical method,--were divorced, and the one
emphasized, favored, and further developed at the expense of the other.
The empiricists hold to the result, while they either weaken or completely
misunderstand the rationalism of the method: the _a priori_ factor, says
Fries, was not reached by _a priori_, but by _a posteriori_, means, and
there is no other way by which it could have been reached. The constructive
thinkers, Fichte and his successors, adopt and continue the metaphysical
method, but reject the empirical result. Fichte's aim is directed to
a system of necessary, unconscious processes of reason, among which,
rejecting the thing in itself, he includes sensation.
According to
Schelling nature itself is _a priori_, a condition of consciousness. This
discrepancy between foundation and result continues in an altered form even
among contemporary thinkers--as a discussion whether the
"main purpose"
of Criticism is to be found in the limitation of knowledge to possible
experience, or the establishment of _a priori_ elements-
-though many, in
adherence to Kant's own view, maintain that the metaphysics of knowledge
and of phenomena (immanent rationalism) is the only legitimate metaphysics.
%1. Theory of Knowledge.
(a) The Pure Intuitions (Transcendental Aesthetic).%--
The first part of the
Critique of Reason, the Transcendental Aesthetic, lays down the position
that _space and time_ are not independent existences, not real beings, and
not properties or relations which would belong to things in themselves
though they were not intuited, but _forms of our intuition_, which have
their basis in the subjective constitution of our, the human, mind. If we
separate from sensuous intuition all that the understanding thinks in it
through its concepts, and all that belongs to sensation, these two forms of
intuition remain, which may be termed pure intuitions, since they can be
considered apart from all sensation. As subjective _conditions_ (lying in
the nature of the subject) through which alone a thing can become an object
of intuition for us, they precede all empirical intuitions or are
_a priori_.
Space and time are neither substantial receptacles which contain all
that is real nor orders inhering in things in themselves, but forms of
intuition. Now all our representations are either pure or empirical in
their origin, and either intuitive or conceptual in character. Kant
advances four proofs for the position that space and time are not empirical
and not concepts, but pure intuitions: (1) Time is not an empirical
concept which has been abstracted from experience. For the coexistence or
succession of phenomena, _i.e._, their existence at the same time or at
different times (from which, as many believe, the representation of time
is abstracted), itself presupposes time--a coexistence or succession is
possible only in time. It is no less false that space is abstracted from
the empirical space relations of external phenomena, their existence
outside and beside one another, or in different places, for it is
impossible to represent relative situation except in space. Therefore
experience does not make space and time possible; but space and time first
of all make experience possible, the one outer, the other inner experience.
They are postulates of perception, not abstractions from it. (2) Time is a
necessary representation _a priori_. We can easily think all phenomena away
from it, but we cannot remove time itself in view of phenomena in general;
we can think time without phenomena, but not phenomena without time. The
same is true of space in reference to external objects.
Both are conditions
of the possibility of phenomena. (3) Time is not a discursive or general
concept. For there is but one time. And different times do not precede the
one time as the constituent parts of which it is made up, but are mere
limitations of it; the part is possible only through the whole. In the same
way the various spaces are only parts of one and the same space, and can
be thought in it alone. But a representation which can be given only by
a single object is a particular representation or an intuition. Because,
therefore, of the oneness of space and time, the representation of each
is an intuition. The _a priori_, immediate intuition of the one space is
entirely different from the empirical, general conception of space, which
is abstracted from the various spaces. (4) Determinate periods of time
arise by limitation of the one, fundamental time.
Consequently this
original time must be unlimited or infinite, and the representation of it
must be an intuition, not a concept. Time contains in itself an endless
number of representations (its parts, times), but this is never the
case with a generic concept, which, indeed, is contained as a partial
representation in an endless number of representations (those of the
individuals having the same name), and, consequently, comprehends them all
under itself, but which never contains them in itself.
The general concept
horse is contained in each particular representation of a horse as a
general characteristic, and that of justice in each representation of a
definite just act; time, however, is not contained in the different times,
but they are contained in it. Similarly the relation of infinite space to
the finite spaces is not the logical relation of a concept to examples of
it, but the intuitive relation of an unlimited whole to its limited parts.
The _Prolegomena_ employs as a fifth proof for the intuitive character of
space, an argument which had already appeared in the essay _On the Ultimate
Ground of the Distinction of Positions in Space_. There are certain spatial
distinctions which can be grasped by intuition alone, and which are
absolutely incapable of comprehension through the understanding--for
example, those of right and left, above and below, before and behind. No
logical marks can be given for the distinction between the object and its
image in the mirror, or between the right ear and the left. The complete
description of a right hand must, in all respects (quality, proportionate
position of parts, size of the whole), hold for the left as well;
but, despite the complete similarity, the one hand cannot be exactly
super-imposed on the other; the glove of the one cannot be worn on the
other. This difference in direction, which has significance only when
viewed from a definite point, and the impossibility mentioned of a
congruence between an object (right hand) and its reflected image (left
hand) can be understood only by intuition; they must be seen and felt, and
cannot be made clear through concepts, and, consequently, can never be
explained to a being which lacks the intuition of space.
In the "transcendental" exposition of space and time Kant follows this
"metaphysical" exposition, which had to prove their non-empirical, and
non-discursive, hence their _a priori_ and intuitive, character, with
the proof that only such an explanation of space and time could make it
conceivable how synthetic cognitions _a priori_ can arise from them. The
principles of mathematics are of this kind. The synthetic character of
geometrical truths is explained by the intuitive nature of space, their
apodictic character by its apriority, and their objective reality or
applicability to empirical objects by the fact that space is the condition
of (external) perception. The like is true of arithmetic and time.
If space were a mere concept, no proposition could be derived from it which
should go beyond the concept and extend our knowledge of its properties.
The possibility of such extension or synthesis in mathematics depends on
the fact that spatial concepts can always be presented or "constructed" in
intuition. The geometrical axiom that in the triangle the sum of two sides
is greater than the third is derived from intuition, by describing the
triangle in imagination or, actually, on the board. Here the object is
given through the cognition and not before it.--If space and time were
empirical representations the knowledge obtained from them would lack
necessity, which, as a matter of fact, it possesses in a marked degree.
While experience teaches us only that something is thus or so, and not that
it could not be otherwise, the axioms, (space has only three dimensions,
time only one; only one straight line is possible between two points),
nay, all the propositions of mathematics are strictly universal and
apodictically certain: we are entirely relieved from the necessity of
measuring all triangles in the world in order to find out whether the sum
of their angles is equal to two right angles, and we do not need, as in the
case of judgments of experience, to add the limitation, so far as it is yet
known there are no exceptions to this rule. The apriority is the _ratio
essendi_ of the strict necessity involved in the "it must be so" _(des
Soseinmüssens_), while the latter is the _ratio cognoscendi_ of the former.
Now since the necessity of mathematical judgments can only be explained
through the ideality of space, this doctrine is perfectly certain, not
merely a probable hypothesis.--The validity of mathematical principles for
all objects of perception, finally, is based on the fact that they are
rules under which alone experience is possible for us.
It should be
mentioned, further, that the conceptions of change and motion (change of
place) are possible only through and in the representation of time. No
concept could make intelligible the possibility of change, that is, of the
connection of contradictory predicates in one and the same thing, but the
intuition of succession easily succeeds in accomplishing it.
The argument is followed by conclusions and explanations based upon it;
(1) Space is the form of the outer, time of the inner, sense. Through the
outer sense external objects are given to us, and through the inner sense
our own inner states. But since all representations, whether they have
external things for their objects or not, belong in themselves, as mental
determinations, to our inner state, time is the formal condition of all
phenomena in general, directly of internal (psychical) phenomena, and,
thereby, indirectly of external phenomena also. (2) The validity of the
relations of space and time cognizable _a priori_ is established for all
objects of possible experience, but is limited to these.
They are valid
for _all phenomena_ (for all things which at any time may be given to our
senses), but only for these, not for things as they are _in themselves_.
They have "empirical reality, but, at the same time, transcendental
ideality." As external phenomena all things are beside one another in
space, and all phenomena whatever are in time and of necessity under
temporal relations; in regard to all things which can occur in our
experience, and in so far as they can occur, space and time are
objectively, therefore empirically, real. But they do not possess absolute
reality (neither subsistent reality nor the reality of inherence); for if
we abstract from our sensuous intuition both vanish, and, apart from the
subject (_N.B._, the transcendental subject, concerning which more below),
they are naught. It is only from man's point of view that we can speak
of space, and of extended, moveable, changeable things; for we can know
nothing concerning the intuitions of other thinking beings, we have no
means of discovering whether they are bound by the same conditions which
limit our intuitions, and which for us are universally valid. (3) Nothing
which is intuited in space is a thing in itself. What we call external
objects are nothing but mere representations of our sensibility, whose
true correlative, the _thing in itself_, cannot be known by ever so deep
penetration into the phenomenon; such properties as belong to things in
themselves can never be given to us through the senses.
Similarly nothing
that is intuited in time is a thing in itself, so that we intuit ourselves
only as we appear to ourselves, and not as we are.
The merely empirical reality of space and time, the limitation of their
validity to phenomena, leaves the certainty of knowledge within the limits
of experience intact; for we are equally certain of it, whether these forms
necessarily belong to things in themselves, or only to our intuitions
of things. The assertion of their absolute reality, on the other hand,
involves us in sheer absurdities (that is, it necessitates the assumption
of two infinite nonentities which exist, but without being anything real,
merely in order to comprehend all reality, and on one of which even our own
existence would be dependent), in view of which the origin of so peculiar
a theory as the idealism of Berkeley appears intelligible. The critical
theory of space and time is so far from being identical with, or akin to,
the theory of Berkeley, that it furnishes the best and only defense against
the latter. If anyone assumes the absolute or transcendental reality of
these forms, it is impossible for him to prevent everything, including even
our own existence, from being changed thereby into mere illusion. But
the critical philosopher is far from degrading bodies to mere illusion;
external phenomena are just as real for him as internal phenomena, though
only as phenomena, it is true, as (possible) representations.
Phenomenon and illusion are not the same. The transcendental distinction
between phenomena and things in themselves must not be confused with the
distinction common to ordinary life and to physics, in accordance with
which we call the rainbow a mere appearance (better, illusion), but the
combination of sun and rain which gives rise to this illusion the thing
in itself, as that which in universal experience and in all different
positions with respect to the senses, is thus and not otherwise determined
in intuition, or that which essentially belongs to the intuition of the
object, and is valid for every human sensibility (in antithesis to that
which only contingently belongs to it, and is valid only for a special
position or organization of this or that sense).
Similarly an object always
appears to grow smaller as its distance increases, while in itself it is
and remains of some fixed size. And this use of words is perfectly
correct, in the _physical or empirical_ sense of "in itself"; but in the
_transcendental_ sense the raindrops, also, together with their form and
size, are themselves mere phenomena, the "in itself" of which remains
entirely unknown to us. Kant, moreover, does not wish to see the
subjectivity of the forms of intuition placed on a level with the
subjectivity of sensations or explained by this, though he accepts it as
a fact long established. The sensations of color, of tone, of temperature
are, no doubt, like the representation of space in that they belong only to
the subjective constitution of the sensibility, and can be attributed to
objects only in relation to our senses. But the great difference between
the two is that these sense qualities may be different in different persons
(the color of the rose may seem different to each eye), or may fail to
harmonize with any human sense; that they are not _a priori_ in the same
strict sense as space and time, and consequently afford no knowledge of the
objects of possible experience independently of perception; and that they
are connected with the phenomenon only as the contingently added effects of
a particular organization, while space, as the condition of external
objects, necessarily belongs to the phenomenon or intuition of them. _It is
through space alone that it is possible for things to be external objects
for us_. The subjectivity of sensation is individual, while that of space
and time is general or universal to mankind; the former is empirical,
individually different, and contingent, the latter _a priori_ and
necessary. Space alone, not sensation, is a _conditio sine qua non_ of
external perception. Space and time are the sole _a priori_ elements of
the sensibility; all other sensuous concepts, even motion and change,
presuppose perception; the movable in space and the succession of
properties in an existing thing are empirical data.
In confirmation of the theory that all objects of the senses are mere
phenomena, the fact is adduced that (with the exception of the will and the
feelings, which are not cognitions) nothing is given us through the senses
but representations of relations, while a thing in itself cannot be known
by mere relations. The phenomenon is a sum total of mere relations. In
regard to matter we know only extension, motion, and the laws of this
motion or forces (attraction, repulsion, impenetrability), but all these
are merely relations of the thing to something, else, that is, external
relations. Where is the inner side which underlies this exterior, and
which belongs to the object in itself? This is never to be found in the
phenomenon, and no matter how far the observation and analysis of nature
may advance (a work with unlimited horizons!) they reach nothing but
portions of space occupied by matter and effects which matter exercises,
that is, nothing beyond that which is comparatively internal, and which,
in its turn, consists of external relations. The absolutely inner side
of matter is a mere fancy; and if the complaint that the
"inner side" of
things is concealed from us is to mean that we do not comprehend what
the things which appear to us may be in themselves, it is unjust and
irrational, for it demands that we should be able to intuit without
senses, in other words, that we should be other than men. The transcendent
questions concerning the noumenon of things are unanswerable; we know
ourselves, even, only as phenomena! A phenomenon consists in nothing but
the relation of something in general to the senses.
It is indubitable _that_ something corresponds to phenomena, which,
by affecting our sensibility, occasions sensations in us, and thereby
phenomena. The very word, the very concept,
"phenomenon", indicates a
relation to something which is not phenomenon, to an object not dependent
on the sensibility. _What_ this may be continues hidden from us, for
knowledge is impossible without intuition. Things in themselves are
unknowable. Nevertheless the idea (it must be confessed, the entirely empty
idea) of this "transcendental object", as an indeterminate somewhat = _x_
which underlies phenomena, is not only allowable, but, as a limiting
concept, unavoidable in order to confine the pretensions of sense to the
only field which is accessible to it, that is, to the field of phenomena.
The inference "space and time are nothing but representations and
representations are in us, therefore space and time as well as all
phenomena in them, bodies with their forces and motions, are in us," does
not accurately express Kant's position, for he might justly reply that,
according to him, bodies as phenomena are in different parts in space from
that which we assign to ourselves, and thus without us; that space is the
form of external intuition, and through it external objects arise for us
from sensations; but that, in regard to the things in themselves which
affect us, we are entirely ignorant whether they are within or without us.
It can easily be shown by literal quotations that there were distinct
tendencies in Kant, especially in the first edition of his principal
work, toward a radical idealism which doubts or denies not merely the
cognizability, but also the existence of objects external to the subject
and its representations, and which degrades the thing in itself to a mere
thought in us, or completely does away with it (_e.g._,
"The representation