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and to enable us to hope for greater success than has fallen to the

lot of our predecessors?

It appears to me that the examples of mathematics and natural

philosophy, which, as we have seen, were brought into their present

condition by a sudden revolution, are sufficiently remarkable to fix

our attention on the essential circumstances of the change which has

proved so advantageous to them, and to induce us to make the

experiment of imitating them, so far as the analogy which, as rational

sciences, they bear to metaphysics may permit. It has hitherto been

assumed that our cognition must conform to the objects; but all

attempts to ascertain anything about these objects a priori, by

means of conceptions, and thus to extend the range of our knowledge,

have been rendered abortive by this assumption. Let us then make the

experiment whether we may not be more successful in metaphysics, if we

assume that the objects must conform to our cognition. This appears,

at all events, to accord better with the possibility of our gaining

the end we have in view, that is to say, of arriving at the

cognition of objects a priori, of determining something with respect

to these objects, before they are given to us. We here propose to do

just what Copernicus did in attempting to explain the celestial

movements. When he found that he could make no progress by assuming

that all the heavenly bodies revolved round the spectator, he reversed

the process, and tried the experiment of assuming that the spectator

revolved, while the stars remained at rest. We may make the same

experiment with regard to the intuition of objects. If the intuition

must conform to the nature of the objects, I do not see how we can

know anything of them a priori. If, on the other hand, the object

conforms to the nature of our faculty of intuition, I can then

easily conceive the possibility of such an a priori knowledge. Now

as I cannot rest in the mere intuitions, but- if they are to become

cognitions- must refer them, as representations, to something, as

object, and must determine the latter by means of the former, here

again there are two courses open to me. Either, first, I may assume

that the conceptions, by which I effect this determination, conform to

the object- and in this case I am reduced to the same perplexity as

before; or secondly, I may assume that the objects, or, which is the

same thing, that experience, in which alone as given objects they

are cognized, conform to my conceptions- and then I am at no loss

how to proceed. For experience itself is a mode of cognition which

requires understanding. Before objects, are given to me, that is, a

priori, I must presuppose in myself laws of the understanding which

are expressed in conceptions a priori. To these conceptions, then, all

the objects of experience must necessarily conform. Now there are

objects which reason thinks, and that necessarily, but which cannot be

given in experience, or, at least, cannot be given so as reason thinks

them. The attempt to think these objects will hereafter furnish an

excellent test of the new method of thought which we have adopted, and

which is based on the principle that we only cognize in things a

priori that which we ourselves place in them.*

*This method, accordingly, which we have borrowed from the natural

philosopher, consists in seeking for the elements of pure reason in

that which admits of confirmation or refutation by experiment. Now the

propositions of pure reason, especially when they transcend the limits

of possible experience, do not admit of our making any experiment with

their objects, as in natural science. Hence, with regard to those

conceptions and principles which we assume a priori, our only course

ill be to view them from two different sides. We must regard one and

the same conception, on the one hand, in relation to experience as

an object of the senses and of the understanding, on the other hand,

in relation to reason, isolated and transcending the limits of

experience, as an object of mere thought. Now if we find that, when we

regard things from this double point of view, the result is in harmony

with the principle of pure reason, but that, when we regard them

from a single point of view, reason is involved in self-contradiction,

then the experiment will establish the correctness of this

distinction.

This attempt succeeds as well as we could desire, and promises to

metaphysics, in its first part- that is, where it is occupied with

conceptions a priori, of which the corresponding objects may be

given in experience- the certain course of science. For by this new

method we are enabled perfectly to explain the possibility of a priori

cognition, and, what is more, to demonstrate satisfactorily the laws

which lie a priori at the foundation of nature, as the sum of the

objects of experience- neither of which was possible according to

the procedure hitherto followed. But from this deduction of the

faculty of a priori cognition in the first part of metaphysics, we

derive a surprising result, and one which, to all appearance,

militates against the great end of metaphysics, as treated in the

second part. For we come to the conclusion that our faculty of

cognition is unable to transcend the limits of possible experience;

and yet this is precisely the most essential object of this science.

The estimate of our rational cognition a priori at which we arrive

is that it has only to do with phenomena, and that things in

themselves, while possessing a real existence, lie beyond its

sphere. Here we are enabled to put the justice of this estimate to the

test. For that which of necessity impels us to transcend the limits of

experience and of all phenomena is the unconditioned, which reason

absolutely requires in things as they are in themselves, in order to

complete the series of conditions. Now, if it appears that when, on

the one hand, we assume that our cognition conforms to its objects

as things in themselves, the unconditioned cannot be thought without

contradiction, and that when, on the other hand, we assume that our

representation of things as they are given to us, does not conform

to these things as they are in themselves, but that these objects,

as phenomena, conform to our mode of representation, the contradiction

disappears: we shall then be convinced of the truth of that which we

began by assuming for the sake of experiment; we may look upon it as

established that the unconditioned does not lie in things as we know

them, or as they are given to us, but in things as they are in

themselves, beyond the range of our cognition.*

*This experiment of pure reason has a great similarity to that of

the chemists, which they term the experiment of reduction, or, more

usually, the synthetic process. The analysis of the metaphysician

separates pure cognition a priori into two heterogeneous elements,

viz., the cognition of things as phenomena, and of things in

themselves. Dialectic combines these again into harmony with the

necessary rational idea of the unconditioned, and finds that this

harmony never results except through the above distinction, which

is, therefore, concluded to be just.

But, after we have thus denied the power of speculative reason to

make any progress in the sphere of the supersensible, it still remains

for our consideration whether data do not exist in practical cognition

which may enable us to determine the transcendent conception of the

unconditioned, to rise beyond the limits of all possible experience

from a practical point of view, and thus to satisfy the great ends

of metaphysics. Speculative reason has thus, at least, made room for

such an extension of our knowledge: and, if it must leave this space

vacant, still it does not rob us of the liberty to fill it up, if we

can, by means of practical data- nay, it even challenges us to make

the attempt.*

*So the central laws of the movements of the heavenly bodies

established the truth of that which Copernicus, first, assumed only as

a hypothesis, and, at the same time, brought to light that invisible

force (Newtonian attraction) which holds the universe together. The

latter would have remained forever undiscovered, if Copernicus had not

ventured on the experiment- contrary to the senses but still just-

of looking for the observed movements not in the heavenly bodies,

but in the spectator. In this Preface I treat the new metaphysical

method as a hypothesis with the view of rendering apparent the first

attempts at such a change of method, which are always hypothetical.

But in the Critique itself it will be demonstrated, not

hypothetically, but apodeictically, from the nature of our

representations of space and time. and from the elementary conceptions

of the understanding.

This attempt to introduce a complete revolution in the procedure

of metaphysics, after the example of the geometricians and natural

philosophers, constitutes the aim of the Critique of Pure

Speculative Reason. It is a treatise on the method to be followed, not

a system of the science itself. But, at the same time, it marks out

and defines both the external boundaries and the internal structure of

this science. For pure speculative reason has this peculiarity,

that, in choosing the various objects of thought, it is able to define

the limits of its own faculties, and even to give a complete

enumeration of the possible modes of proposing problems to itself, and

thus to sketch out the entire system of metaphysics. For, on the one

hand, in cognition a priori, nothing must be attributed to the objects

but what the thinking subject derives from itself; and, on the other

hand, reason is, in regard to the principles of cognition, a perfectly

distinct, independent unity, in which, as in an organized body,

every member exists for the sake of the others, and all for the sake

of each, so that no principle can be viewed, with safety, in one

relationship, unless it is, at the same time, viewed in relation to

the total use of pure reason. Hence, too, metaphysics has this

singular advantage- an advantage which falls to the lot of no other

science which has to do with objects- that, if once it is conducted

into the sure path of science, by means of this criticism, it can then

take in the whole sphere of its cognitions, and can thus complete

its work, and leave it for the use of posterity, as a capital which

can never receive fresh accessions. For metaphysics has to deal only

with principles and with the limitations of its own employment as

determined by these principles. To this perfection it is, therefore,

bound, as the fundamental science, to attain, and to it the maxim

may justly be applied:

Nil actum reputans, si quid superesset agendum.*

*"He considered nothing done, so long as anything remained to be

done."

But, it will be asked, what kind of a treasure is this that we

propose to bequeath to posterity? What is the real value of this

system of metaphysics, purified by criticism, and thereby reduced to a

permanent condition? A cursory view of the present work will lead to

the supposition that its use is merely negative, that it only serves

to warn us against venturing, with speculative reason, beyond the

limits of experience. This is, in fact, its primary use. But this,

at once, assumes a positive value, when we observe that the principles

with which speculative reason endeavours to transcend its limits

lead inevitably, not to the extension, but to the contraction of the

use of reason, inasmuch as they threaten to extend the limits of

sensibility, which is their proper sphere, over the entire realm of

thought and, thus, to supplant the pure (practical) use of reason.

So far, then, as this criticism is occupied in confining speculative

reason within its proper bounds, it is only negative; but, inasmuch as

it thereby, at the same time, removes an obstacle which impedes and

even threatens to destroy the use of practical reason, it possesses

a positive and very important value. In order to admit this, we have

only to be convinced that there is an absolutely necessary use of pure

reason- the moral use- in which it inevitably transcends the limits of

sensibility, without the aid of speculation, requiring only to be

insured against the effects of a speculation which would involve it in

contradiction with itself. To deny the positive advantage of the

service which this criticism renders us would be as absurd as. to

maintain that the system of police is productive of no positive

benefit, since its main business is to prevent the violence which

citizen has to apprehend from citizen, that so each may pursue his

vocation in peace and security. That space and time are only forms

of sensible intuition, and hence are only conditions of the

existence of things as phenomena; that, moreover, we have no

conceptions of the understanding, and, consequently, no elements for

the cognition of things, except in so far as a corresponding intuition

can be given to these conceptions; that, accordingly, we can have no

cognition of an object, as a thing in itself, but only as an object of

sensible intuition, that is, as phenomenon- all this is proved in

the analytical part of the Critique; and from this the limitation of

all possible speculative cognition to the mere objects of

experience, follows as a necessary result. At the same time, it must

be carefully borne in mind that, while we surrender the power of

cognizing, we still reserve the power of thinking objects, as things

in themselves.* For, otherwise, we should require to affirm the

existence of an appearance, without something that appears- which

would be absurd. Now let us suppose, for a moment, that we had not

undertaken this criticism and, accordingly, had not drawn the

necessary distinction between things as objects of experience and

things as they are in themselves. The principle of causality, and,

by consequence, the mechanism of nature as determined by causality,

would then have absolute validity in relation to all things as

efficient causes. I should then be unable to assert, with regard to