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 won't
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

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

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