INTRODUCTION.
I. Of the difference between Pure and Empirical Knowledge
That all our knowledge begins with experience there can be no doubt.
For how is it possible that the faculty of cognition should be
awakened into exercise otherwise than by means of objects which affect
our senses, and partly of themselves produce representations, partly
rouse our powers of understanding into activity, to compare to
connect, or to separate these, and so to convert the raw material of
our sensuous impressions into a knowledge of objects, which is
called experience? In respect of time, therefore, no knowledge of ours
is antecedent to experience, but begins with it.
But, though all our knowledge begins with experience, it by no means
follows that all arises out of experience. For, on the contrary, it is
quite possible that our empirical knowledge is a compound of that
which we receive through impressions, and that which the faculty of
cognition supplies from itself (sensuous impressions giving merely the
occasion), an addition which we cannot distinguish from the original
element given by sense, till long practice has made us attentive to,
and skilful in separating it. It is, therefore, a question which
requires close investigation, and not to be answered at first sight,
whether there exists a knowledge altogether independent of experience,
and even of all sensuous impressions? Knowledge of this kind is called
a priori, in contradistinction to empirical knowledge, which has its
sources a posteriori, that is, in experience.
But the expression, "a priori," is not as yet definite enough
adequately to indicate the whole meaning of the question above
started. For, in speaking of knowledge which has its sources in
experience, we are wont to say, that this or that may be known a
priori, because we do not derive this knowledge immediately from
experience, but from a general rule, which, however, we have itself
borrowed from experience. Thus, if a man undermined his house, we say,
"he might know a priori that it would have fallen;" that is, he needed
not to have waited for the experience that it did actually fall. But
still, a priori, he could not know even this much. For, that bodies
are heavy, and, consequently, that they fall when their supports are
taken away, must have been known to him previously, by means of
experience.
By the term "knowledge a priori," therefore, we shall in the
sequel understand, not such as is independent of this or that kind
of experience, but such as is absolutely so of all experience. Opposed
to this is empirical knowledge, or that which is possible only a
posteriori, that is, through experience. Knowledge a priori is
either pure or impure. Pure knowledge a priori is that with which no
empirical element is mixed up. For example, the proposition, "Every
change has a cause," is a proposition a priori, but impure, because
change is a conception which can only be derived from experience.
II. The Human Intellect, even in an Unphilosophical State,
is in Possession of Certain Cognitions "a priori".
The question now is as to a criterion, by which we may securely
distinguish a pure from an empirical cognition. Experience no doubt
teaches us that this or that object is constituted in such and such
a manner, but not that it could not possibly exist otherwise. Now,
in the first place, if we have a proposition which contains the idea
of necessity in its very conception, it is a if, moreover, it is not
derived from any other proposition, unless from one equally
involving the idea of necessity, it is absolutely priori. Secondly, an
empirical judgement never exhibits strict and absolute, but only
assumed and comparative universality (by induction); therefore, the
most we can say is- so far as we have hitherto observed, there is no
exception to this or that rule. If, on the other hand, a judgement
carries with it strict and absolute universality, that is, admits of
no possible exception, it is not derived from experience, but is valid
absolutely a priori.
Empirical universality is, therefore, only an arbitrary extension of
validity, from that which may be predicated of a proposition valid
in most cases, to that which is asserted of a proposition which
holds good in all; as, for example, in the affirmation, "All bodies
are heavy." When, on the contrary, strict universality characterizes a
judgement, it necessarily indicates another peculiar source of
knowledge, namely, a faculty of cognition a priori. Necessity and
strict universality, therefore, are infallible tests for
distinguishing pure from empirical knowledge, and are inseparably
connected with each other. But as in the use of these criteria the
empirical limitation is sometimes more easily detected than the
contingency of the judgement, or the unlimited universality which we
attach to a judgement is often a more convincing proof than its
necessity, it may be advisable to use the criteria separately, each
being by itself infallible.
Now, that in the sphere of human cognition we have judgements
which are necessary, and in the strictest sense universal,
consequently pure a priori, it will be an easy matter to show. If we
desire an example from the sciences, we need only take any proposition
in mathematics. If we cast our eyes upon the commonest operations of
the understanding, the proposition, "Every change must have a
cause," will amply serve our purpose. In the latter case, indeed,
the conception of a cause so plainly involves the conception of a
necessity of connection with an effect, and of a strict universality
of the law, that the very notion of a cause would entirely
disappear, were we to derive it, like Hume, from a frequent
association of what happens with that which precedes; and the habit
thence originating of connecting representations- the necessity
inherent in the judgement being therefore merely subjective.
Besides, without seeking for such examples of principles existing a
priori in cognition, we might easily show that such principles are the
indispensable basis of the possibility of experience itself, and
consequently prove their existence a priori. For whence could our
experience itself acquire certainty, if all the rules on which it
depends were themselves empirical, and consequently fortuitous? No
one, therefore, can admit the validity of the use of such rules as
first principles. But, for the present, we may content ourselves
with having established the fact, that we do possess and exercise a
faculty of pure a priori cognition; and, secondly, with having pointed
out the proper tests of such cognition, namely, universality and
necessity.
Not only in judgements, however, but even in conceptions, is an a
priori origin manifest. For example, if we take away by degrees from
our conceptions of a body all that can be referred to mere sensuous
experience- colour, hardness or softness, weight, even
impenetrability- the body will then vanish; but the space which it
occupied still remains, and this it is utterly impossible to
annihilate in thought. Again, if we take away, in like manner, from
our empirical conception of any object, corporeal or incorporeal,
all properties which mere experience has taught us to connect with it,
still we cannot think away those through which we cogitate it as
substance, or adhering to substance, although our conception of
substance is more determined than that of an object. Compelled,
therefore, by that necessity with which the conception of substance
forces itself upon us, we must confess that it has its seat in our
faculty of cognition a priori.
III. Philosophy stands in need of a Science which shall
Determine the Possibility, Principles, and Extent of
Human Knowledge "a priori"
Of far more importance than all that has been above said, is the
consideration that certain of our cognitions rise completely above the
sphere of all possible experience, and by means of conceptions, to
which there exists in the whole extent of experience no
corresponding object, seem to extend the range of our judgements
beyond its bounds. And just in this transcendental or supersensible
sphere, where experience affords us neither instruction nor
guidance, lie the investigations of reason, which, on account of their
importance, we consider far preferable to, and as having a far more
elevated aim than, all that the understanding can achieve within the
sphere of sensuous phenomena. So high a value do we set upon these
investigations, that even at the risk of error, we persist in
following them out, and permit neither doubt nor disregard nor
indifference to restrain us from the pursuit. These unavoidable
problems of mere pure reason are God, freedom (of will), and
immortality. The science which, with all its preliminaries, has for
its especial object the solution of these problems is named
metaphysics- a science which is at the very outset dogmatical, that
is, it confidently takes upon itself the execution of this task
without any previous investigation of the ability or inability of
reason for such an undertaking.
Now the safe ground of experience being thus abandoned, it seems
nevertheless natural that we should hesitate to erect a building
with the cognitions we possess, without knowing whence they come,
and on the strength of principles, the origin of which is
undiscovered. Instead of thus trying to build without a foundation, it
is rather to be expected that we should long ago have put the
question, how the understanding can arrive at these a priori
cognitions, and what is the extent, validity, and worth which they may
possess? We say, "This is natural enough," meaning by the word
natural, that which is consistent with a just and reasonable way of
thinking; but if we understand by the term, that. which usually
happens, nothing indeed could be more natural and more
comprehensible than that this investigation should be left long
unattempted. For one part of our pure knowledge, the science of
mathematics, has been long firmly established, and thus leads us to
form flattering expectations with regard to others, though these may
be of quite a different nature. Besides, when we get beyond the bounds
of experience, we are of course safe from opposition in that
quarter; and the charm of widening the range of our knowledge is so
great that, unless we are brought to a standstill by some evident
contradiction, we hurry on undoubtingly in our course. This,
however, may be avoided, if we are sufficiently cautious in the
construction of our fictions, which are not the less fictions on
that account.
Mathematical science affords us a brilliant example, how far,
independently of all experience, we may carry our a priori
knowledge. It is true that the mathematician occupies himself with
objects and cognitions only in so far as they can be represented by
means of intuition. But this circumstance is easily overlooked,
because the said intuition can itself be given a priori, and therefore
is hardly to be distinguished from a mere pure conception. Deceived by
such a proof of the power of reason, we can perceive no limits to
the extension of our knowledge. The light dove cleaving in free flight
the thin air, whose resistance it feels, might imagine that her
movements would be far more free and rapid in airless space. just in
the same way did Plato, abandoning the world of sense because of the
narrow limits it sets to the understanding, venture upon the wings
of ideas beyond it, into the void space of pure intellect. He did
not reflect that he made no real progress by all his efforts; for he
met with no resistance which might serve him for a support, as it
were, whereon to rest, and on which he might apply his powers, in
order to let the intellect acquire momentum for its progress. It is,
indeed, the common fate of human reason in speculation, to finish
the imposing edifice of thought as rapidly as possible, and then for
the first time to begin to examine whether the foundation is a solid
one or no. Arrived at this point, all sorts of excuses are sought
after, in order to console us for its want of stability, or rather,
indeed, to enable Us to dispense altogether with so late and dangerous
an investigation. But what frees us during the process of building
from all apprehension or suspicion, and flatters us into the belief of
its solidity, is this. A great part, perhaps the greatest part, of the
business of our reason consists in the analysation of the
conceptions which we already possess of objects. By this means we gain
a multitude of cognitions, which although really nothing more than
elucidations or explanations of that which (though in a confused
manner) was already thought in our conceptions, are, at least in
respect of their form, prized as new introspections; whilst, so far as
regards their matter or content, we have really made no addition to
our conceptions, but only disinvolved them. But as this process does
furnish a real priori knowledge, which has a sure progress and
useful results, reason, deceived by this, slips in, without being
itself aware of it, assertions of a quite different kind; in which, to
given conceptions it adds others, a priori indeed, but entirely
foreign to them, without our knowing how it arrives at these, and,
indeed, without such a question ever suggesting itself. I shall
therefore at once proceed to examine the difference between these
two modes of knowledge.
IV. Of the Difference Between Analytical and Synthetical Judgements.
In all judgements wherein the relation of a subject to the predicate
is cogitated (I mention affirmative judgements only here; the
application to negative will be very easy), this relation is
possible in two different ways. Either the predicate B belongs to
the subject A, as somewhat which is contained (though covertly) in the
conception A; or the predicate B lies completely out of the conception
A, although it stands in connection with it. In the first instance,
I term the judgement analytical, in the second, synthetical.
Analytical judgements (affirmative) are therefore those in which the
connection of the predicate with the subject is cogitated through
identity; those in which this connection is cogitated without
identity, are called synthetical judgements. The former may be
called explicative, the latter augmentative judgements; because the
former add in the predicate nothing to the conception of the
subject, but only analyse it into its constituent conceptions, which
were thought already in the subject, although in a confused manner;
the latter add to our conceptions of the subject a predicate which was
not contained in it, and which no analysis could ever have
discovered therein. For example, when I say, "All bodies are
extended," this is an analytical judgement. For I need not go beyond
the conception of body in order to find extension connected with it,
but merely analyse the conception, that is, become conscious of the
manifold properties which I think in that conception, in order to
discover this predicate in it: it is therefore an analytical
judgement. On the other hand, when I say, "All bodies are heavy,"
the predicate is something totally different from that which I think
in the mere conception of a body. By the addition of such a predicate,
therefore, it becomes a synthetical judgement.
Judgements of experience, as such, are always synthetical. For it
would be absurd to think of grounding an analytical judgement on
experience, because in forming such a judgement I need not go out of
the sphere of my conceptions, and therefore recourse to the
testimony of experience is quite unnecessary. That "bodies are
extended" is not an empirical judgement, but a proposition which
stands firm a priori. For before addressing myself to experience, I
already have in my conception all the requisite conditions for the
judgement, and I have only to extract the predicate from the
conception, according to the principle of contradiction, and thereby
at the same time become conscious of the necessity of the judgement, a
necessity which I could never learn from experience. On the other
hand, though at first I do not at all include the predicate of
weight in my conception of body in general, that conception still
indicates an object of experience, a part of the totality of
experience, to which I can still add other parts; and this I do when I
recognize by observation that bodies are heavy. I can cognize
beforehand by analysis the conception of body through the
characteristics of extension, impenetrability, shape, etc., all
which are cogitated in this conception. But now I extend my knowledge,
and looking back on experience from which I had derived this
conception of body, I find weight at all times connected with the
above characteristics, and therefore I synthetically add to my
conceptions this as a predicate, and say, "All bodies are heavy." Thus
it is experience upon which rests the possibility of the synthesis
of the predicate of weight with the conception of body, because both
conceptions, although the one is not contained in the other, still
belong to one another (only contingently, however), as parts of a
whole, namely, of experience, which is itself a synthesis of
intuitions.
But to synthetical judgements a priori, such aid is entirely
wanting. If I go out of and beyond the conception A, in order to
recognize another B as connected with it, what foundation have I to
rest on, whereby to render the synthesis possible? I have here no
longer the advantage of looking out in the sphere of experience for
what I want. Let us take, for example, the proposition, "Everything
that happens has a cause." In the conception of "something that
happens," I indeed think an existence which a certain time
antecedes, and from this I can derive analytical judgements. But the
conception of a cause lies quite out of the above conception, and
indicates something entirely different from "that which happens,"
and is consequently not contained in that conception. How then am I
able to assert concerning the general conception- "that which
happens"- something entirely different from that conception, and to
recognize the conception of cause although not contained in it, yet as
belonging to it, and even necessarily? what is here the unknown = X,
upon which the understanding rests when it believes it has found,
out of the conception A a foreign predicate B, which it nevertheless
considers to be connected with it? It cannot be experience, because
the principle adduced annexes the two representations, cause and
effect, to the representation existence, not only with universality,
which experience cannot give, but also with the expression of
necessity, therefore completely a priori and from pure conceptions.
Upon such synthetical, that is augmentative propositions, depends
the whole aim of our speculative knowledge a priori; for although
analytical judgements are indeed highly important and necessary,
they are so, only to arrive at that clearness of conceptions which
is requisite for a sure and extended synthesis, and this alone is a
real acquisition.
V. In all Theoretical Sciences of Reason, Synthetical Judgements
"a priori" are contained as Principles.
1. Mathematical judgements are always synthetical. Hitherto this
fact, though incontestably true and very important in its
consequences, seems to have escaped the analysts of the human mind,
nay, to be in complete opposition to all their conjectures. For as
it was found that mathematical conclusions all proceed according to
the principle of contradiction (which the nature of every apodeictic
certainty requires), people became persuaded that the fundamental
principles of the science also were recognized and admitted in the
same way. But the notion is fallacious; for although a synthetical
proposition can certainly be discerned by means of the principle of
contradiction, this is possible only when another synthetical
proposition precedes, from which the latter is deduced, but never of
itself which
Before all, be it observed, that proper mathematical propositions
are always judgements a priori, and not empirical, because they
carry along with them the conception of necessity, which cannot be
given by experience. If this be demurred to, it matters not; I will
then limit my assertion to pure mathematics, the very conception of
which implies that it consists of knowledge altogether non-empirical
and a priori.
We might, indeed at first suppose that the proposition 7 + 5 = 12 is
a merely analytical proposition, following (according to the principle
of contradiction) from the conception of a sum of seven and five.
But if we regard it more narrowly, we find that our conception of
the sum of seven and five contains nothing more than the uniting of
both sums into one, whereby it cannot at all be cogitated what this
single number is which embraces both. The conception of twelve is by
no means obtained by merely cogitating the union of seven and five;
and we may analyse our conception of such a possible sum as long as we
will, still we shall never discover in it the notion of twelve. We
must go beyond these conceptions, and have recourse to an intuition
which corresponds to one of the two- our five fingers, for example, or
like Segner in his Arithmetic five points, and so by degrees, add
the units contained in the five given in the intuition, to the
conception of seven. For I first take the number 7, and, for the
conception of 5 calling in the aid of the fingers of my hand as
objects of intuition, I add the units, which I before took together to
make up the number 5, gradually now by means of the material image
my hand, to the number 7, and by this process, I at length see the
number 12 arise. That 7 should be added to 5, I have certainly
cogitated in my conception of a sum = 7 + 5, but not that this sum was
equal to 12. Arithmetical propositions are therefore always
synthetical, of which we may become more clearly convinced by trying
large numbers. For it will thus become quite evident that, turn and
twist our conceptions as we may, it is impossible, without having
recourse to intuition, to arrive at the sum total or product by
means of the mere analysis of our conceptions. just as little is any
principle of pure geometry analytical. "A straight line between two
points is the shortest," is a synthetical proposition. For my
conception of straight contains no notion of quantity, but is merely
qualitative. The conception of the shortest is therefore fore wholly
an addition, and by no analysis can it be extracted from our
conception of a straight line. Intuition must therefore here lend
its aid, by means of which, and thus only, our synthesis is possible.
Some few principles preposited by geometricians are, indeed,
really analytical, and depend on the principle of contradiction.
They serve, however, like identical propositions, as links in the
chain of method, not as principles- for example, a = a, the whole is
equal to itself, or (a+b) > a, the whole is greater than its part. And
yet even these principles themselves, though they derive their
validity from pure conceptions, are only admitted in mathematics
because they can be presented in intuition. What causes us here
commonly to believe that the predicate of such apodeictic judgements
is already contained in our conception, and that the judgement is
therefore analytical, is merely the equivocal nature of the
expression. We must join in thought a certain predicate to a given
conception, and this necessity cleaves already to the conception.
But the question is, not what we must join in thought to the given
conception, but what we really think therein, though only obscurely,
and then it becomes manifest that the predicate pertains to these
conceptions, necessarily indeed, yet not as thought in the
conception itself, but by virtue of an intuition, which must be
added to the conception.
2. The science of natural philosophy (physics) contains in itself
synthetical judgements a priori, as principles. I shall adduce two
propositions. For instance, the proposition, "In all changes of the
material world, the quantity of matter remains unchanged"; or, that,
"In all communication of motion, action and reaction must always be
equal." In both of these, not only is the necessity, and therefore
their origin a priori clear, but also that they are synthetical
propositions. For in the conception of matter, I do not cogitate its
permanency, but merely its presence in space, which it fills. I
therefore really go out of and beyond the conception of matter, in
order to think on to it something a priori, which I did not think in
it. The proposition is therefore not analytical, but synthetical,
and nevertheless conceived a priori; and so it is with regard to the
other propositions of the pure part of natural philosophy.
3. As to metaphysics, even if we look upon it merely as an attempted
science, yet, from the nature of human reason, an indispensable one,
we find that it must contain synthetical propositions a priori. It
is not merely the duty of metaphysics to dissect, and thereby
analytically to illustrate the conceptions which we form a priori of
things; but we seek to widen the range of our a priori knowledge.
For this purpose, we must avail ourselves of such principles as add
something to the original conception- something not identical with,
nor contained in it, and by means of synthetical judgements a
priori, leave far behind us the limits of experience; for example,
in the proposition, "the world must have a beginning," and such
like. Thus metaphysics, according to the proper aim of the science,
consists merely of synthetical propositions a priori.
VI. The Universal Problem of Pure Reason.
It is extremely advantageous to be able to bring a number of
investigations under the formula of a single problem. For in this
manner, we not only facilitate our own labour, inasmuch as we define
it clearly to ourselves, but also render it more easy for others to
decide whether we have done justice to our undertaking. The proper
problem of pure reason, then, is contained in the question: "How are
synthetical judgements a priori possible?"
That metaphysical science has hitherto remained in so vacillating
a state of uncertainty and contradiction, is only to be attributed
to the fact that this great problem, and perhaps even the difference
between analytical and synthetical judgements, did not sooner
suggest itself to philosophers. Upon the solution of this problem,
or upon sufficient proof of the impossibility of synthetical knowledge
a priori, depends the existence or downfall of the science of
metaphysics. Among philosophers, David Hume came the nearest of all to
this problem; yet it never acquired in his mind sufficient
precision, nor did he regard the question in its universality. On
the contrary, he stopped short at the synthetical proposition of the
connection of an effect with its cause (principium causalitatis),
insisting that such proposition a priori was impossible. According
to his conclusions, then, all that we term metaphysical science is a
mere delusion, arising from the fancied insight of reason into that
which is in truth borrowed from experience, and to which habit has
given the appearance of necessity. Against this assertion, destructive
to all pure philosophy, he would have been guarded, had he had our
problem before his eyes in its universality. For he would then have
perceived that, according to his own argument, there likewise could
not be any pure mathematical science, which assuredly cannot exist
without synthetical propositions a priori- an absurdity from which his
good understanding must have saved him.
In the solution of the above problem is at the same time
comprehended the possibility of the use of pure reason in the
foundation and construction of all sciences which contain
theoretical knowledge a priori of objects, that is to say, the
answer to the following questions:
How is pure mathematical science possible?
How is pure natural science possible?
Respecting these sciences, as they do certainly exist, it may with
propriety be asked, how they are possible?- for that they must be
possible is shown by the fact of their really existing.* But as to
metaphysics, the miserable progress it has hitherto made, and the fact
that of no one system yet brought forward, far as regards its true
aim, can it be said that this science really exists, leaves any one at
liberty to doubt with reason the very possibility of its existence.
*As to the existence of pure natural science, or physics, perhaps
many may still express doubts. But we have only to look at the
different propositions which are commonly treated of at the
commencement of proper (empirical) physical science- those, for
example, relating to the permanence of the same quantity of matter,
the vis inertiae, the equality of action and reaction, etc.- to be
soon convinced that they form a science of pure physics (physica pura,
or rationalis), which well deserves to be separately exposed as a
special science, in its whole extent, whether that be great or
confined.
Yet, in a certain sense, this kind of knowledge must
unquestionably be looked upon as given; in other words, metaphysics
must be considered as really existing, if not as a science,
nevertheless as a natural disposition of the human mind (metaphysica
naturalis). For human reason, without any instigations imputable to
the mere vanity of great knowledge, unceasingly progresses, urged on
by its own feeling of need, towards such questions as cannot be
answered by any empirical application of reason, or principles derived
therefrom; and so there has ever really existed in every man some
system of metaphysics. It will always exist, so soon as reason
awakes to the exercise of its power of speculation. And now the
question arises: "How is metaphysics, as a natural disposition,
possible?" In other words, how, from the nature of universal human
reason, do those questions arise which pure reason proposes to itself,
and which it is impelled by its own feeling of need to answer as
well as it can?
But as in all the attempts hitherto made to answer the questions
which reason is prompted by its very nature to propose to itself,
for example, whether the world had a beginning, or has existed from
eternity, it has always met with unavoidable contradictions, we must
not rest satisfied with the mere natural disposition of the mind to
metaphysics, that is, with the existence of the faculty of pure
reason, whence, indeed, some sort of metaphysical system always
arises; but it must be possible to arrive at certainty in regard to
the question whether we know or do not know the things of which
metaphysics treats. We must be able to arrive at a decision on the
subjects of its questions, or on the ability or inability of reason to
form any judgement respecting them; and therefore either to extend
with confidence the bounds of our pure reason, or to set strictly
defined and safe limits to its action. This last question, which
arises out of the above universal problem, would properly run thus:
"How is metaphysics possible as a science?"
Thus, the critique of reason leads at last, naturally and
necessarily, to science; and, on the other hand, the dogmatical use of
reason without criticism leads to groundless assertions, against which
others equally specious can always be set, thus ending unavoidably
in scepticism.
Besides, this science cannot be of great and formidable prolixity,
because it has not to do with objects of reason, the variety of
which is inexhaustible, but merely with Reason herself and her
problems; problems which arise out of her own bosom, and are not
proposed to her by the nature of outward things, but by her own
nature. And when once Reason has previously become able completely
to understand her own power in regard to objects which she meets
with in experience, it will be easy to determine securely the extent
and limits of her attempted application to objects beyond the confines
of experience.
We may and must, therefore, regard the attempts hitherto made to
establish metaphysical science dogmatically as non-existent. For
what of analysis, that is, mere dissection of conceptions, is
contained in one or other, is not the aim of, but only a preparation
for metaphysics proper, which has for its object the extension, by
means of synthesis, of our a priori knowledge. And for this purpose,
mere analysis is of course useless, because it only shows what is
contained in these conceptions, but not how we arrive, a priori, at
them; and this it is her duty to show, in order to be able
afterwards to determine their valid use in regard to all objects of
experience, to all knowledge in general. But little self-denial,
indeed, is needed to give up these pretensions, seeing the undeniable,
and in the dogmatic mode of procedure, inevitable contradictions of
Reason with herself, have long since ruined the reputation of every
system of metaphysics that has appeared up to this time. It will
require more firmness to remain undeterred by difficulty from
within, and opposition from without, from endeavouring, by a method
quite opposed to all those hitherto followed, to further the growth
and fruitfulness of a science indispensable to human reason- a science
from which every branch it has borne may be cut away, but whose
roots remain indestructible.
VII. Idea and Division of a Particular Science, under the
Name of a Critique of Pure Reason.
From all that has been said, there results the idea of a
particular science, which may be called the Critique of Pure Reason.
For reason is the faculty which furnishes us with the principles of
knowledge a priori. Hence, pure reason is the faculty which contains
the principles of cognizing anything absolutely a priori. An organon
of pure reason would be a compendium of those principles according
to which alone all pure cognitions a priori can be obtained. The
completely extended application of such an organon would afford us a
system of pure reason. As this, however, is demanding a great deal,
and it is yet doubtful whether any extension of our knowledge be
here possible, or, if so, in what cases; we can regard a science of
the mere criticism of pure reason, its sources and limits, as the
propaedeutic to a system of pure reason. Such a science must not be
called a doctrine, but only a critique of pure reason; and its use, in
regard to speculation, would be only negative, not to enlarge the
bounds of, but to purify, our reason, and to shield it against
error- which alone is no little gain. I apply the term
transcendental to all knowledge which is not so much occupied with
objects as with the mode of our cognition of these objects, so far
as this mode of cognition is possible a priori. A system of such
conceptions would be called transcendental philosophy. But this,
again, is still beyond the bounds of our present essay. For as such
a science must contain a complete exposition not only of our
synthetical a priori, but of our analytical a priori knowledge, it
is of too wide a range for our present purpose, because we do not
require to carry our analysis any farther than is necessary to
understand, in their full extent, the principles of synthesis a
priori, with which alone we have to do. This investigation, which we
cannot properly call a doctrine, but only a transcendental critique,
because it aims not at the enlargement, but at the correction and
guidance, of our knowledge, and is to serve as a touchstone of the
worth or worthlessness of all knowledge a priori, is the sole object
of our present essay. Such a critique is consequently, as far as
possible, a preparation for an organon; and if this new organon should
be found to fail, at least for a canon of pure reason, according to
which the complete system of the philosophy of pure reason, whether it
extend or limit the bounds of that reason, might one day be set
forth both analytically and synthetically. For that this is
possible, nay, that such a system is not of so great extent as to
preclude the hope of its ever being completed, is evident. For we have
not here to do with the nature of outward objects, which is
infinite, but solely with the mind, which judges of the nature of
objects, and, again, with the mind only in respect of its cognition
a priori. And the object of our investigations, as it is not to be
sought without, but, altogether within, ourselves, cannot remain
concealed, and in all probability is limited enough to be completely
surveyed and fairly estimated, according to its worth or
worthlessness. Still less let the reader here expect a critique of
books and systems of pure reason; our present object is exclusively
a critique of the faculty of pure reason itself. Only when we make
this critique our foundation, do we possess a pure touchstone for
estimating the philosophical value of ancient and modern writings on
this subject; and without this criterion, the incompetent historian or
judge decides upon and corrects the groundless assertions of others
with his own, which have themselves just as little foundation.
Transcendental philosophy is the idea of a science, for which the
Critique of Pure Reason must sketch the whole plan
architectonically, that is, from principles, with a full guarantee for
the validity and stability of all the parts which enter into the
building. It is the system of all the principles of pure reason. If
this Critique itself does not assume the title of transcendental
philosophy, it is only because, to be a complete system, it ought to
contain a full analysis of all human knowledge a priori. Our
critique must, indeed, lay before us a complete enumeration of all the
radical conceptions which constitute the said pure knowledge. But from
the complete analysis of these conceptions themselves, as also from
a complete investigation of those derived from them, it abstains
with reason; partly because it would be deviating from the end in view
to occupy itself with this analysis, since this process is not
attended with the difficulty and insecurity to be found in the
synthesis, to which our critique is entirely devoted, and partly
because it would be inconsistent with the unity of our plan to
burden this essay with the vindication of the completeness of such
an analysis and deduction, with which, after all, we have at present
nothing to do. This completeness of the analysis of these radical
conceptions, as well as of the deduction from the conceptions a priori
which may be given by the analysis, we can, however, easily attain,
provided only that we are in possession of all these radical
conceptions, which are to serve as principles of the synthesis, and
that in respect of this main purpose nothing is wanting.
To the Critique of Pure Reason, therefore, belongs all that
constitutes transcendental philosophy; and it is the complete idea
of transcendental philosophy, but still not the science itself;
because it only proceeds so far with the analysis as is necessary to
the power of judging completely of our synthetical knowledge a priori.
The principal thing we must attend to, in the division of the
parts of a science like this, is that no conceptions must enter it
which contain aught empirical; in other words, that the knowledge a
priori must be completely pure. Hence, although the highest principles
and fundamental conceptions of morality are certainly cognitions a
priori, yet they do not belong to transcendental philosophy;
because, though they certainly do not lay the conceptions of pain,
pleasure, desires, inclinations, etc. (which are all of empirical
origin), at the foundation of its precepts, yet still into the
conception of duty- as an obstacle to be overcome, or as an incitement
which should not be made into a motive- these empirical conceptions
must necessarily enter, in the construction of a system of pure
morality. Transcendental philosophy is consequently a philosophy of
the pure and merely speculative reason. For all that is practical,
so far as it contains motives, relates to feelings, and these belong
to empirical sources of cognition.
If we wish to divide this science from the universal point of view
of a science in general, it ought to comprehend, first, a Doctrine
of the Elements, and, secondly, a Doctrine of the Method of pure
reason. Each of these main divisions will have its subdivisions, the
separate reasons for which we cannot here particularize. Only so
much seems necessary, by way of introduction of premonition, that
there are two sources of human knowledge (which probably spring from a
common, but to us unknown root), namely, sense and understanding. By
the former, objects are given to us; by the latter, thought. So far as
the faculty of sense may contain representations a priori, which
form the conditions under which objects are given, in so far it
belongs to transcendental philosophy. The transcendental doctrine of
sense must form the first part of our science of elements, because the
conditions under which alone the objects of human knowledge are
given must precede those under which they are thought.
