The Critique of Pure Reason. Immanuel Kant
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conditions under which the understanding is exercised; for example, the influence of the senses, the play of the fantasy or imagination, the laws of the memory, the force of habit, of inclination, etc., consequently also, the sources of prejudice — in a word, we abstract all causes from which particular cognitions arise, because these causes regard the understanding under certain circumstances of its application, and, to the knowledge of them experience is required. Pure general logic has to do, therefore, merely with pure a priori principles, and is a canon of understanding and reason, but only in respect of the formal part of their use, be the content what it may, empirical or transcendental. General logic is called applied, when it is directed to the laws of the use of the understanding, under the subjective empirical conditions which psychology teaches us. It has therefore empirical principles, although, at the same time, it is in so far general, that it applies to the exercise of the understanding, without regard to the difference of objects. On this account, moreover, it is neither a canon of the understanding in general, nor an organon of a particular science, but merely a cathartic of the human understanding.
In general logic, therefore, that part which constitutes pure logic must be carefully distinguished from that which constitutes applied (though still general) logic. The former alone is properly science, although short and dry, as the methodical exposition of an elemental doctrine of the understanding ought to be. In this, therefore, logicians must always bear in mind two rules:
1 As general logic, it makes abstraction of all content of the cognition of the understanding, and of the difference of objects, and has to do with nothing but the mere form of thought.
2 As pure logic, it has no empirical principles, and consequently draws nothing (contrary to the common persuasion) from psychology, which therefore has no influence on the canon of the understanding. It is a demonstrated doctrine, and everything in it must be certain completely a priori.
What I called applied logic (contrary to the common acceptation of this term, according to which it should contain certain exercises for the scholar, for which pure logic gives the rules), is a representation of the understanding, and of the rules of its necessary employment in concreto, that is to say, under the accidental conditions of the subject, which may either hinder or promote this employment, and which are all given only empirically. Thus applied logic treats of attention, its impediments and consequences, of the origin of error, of the state of doubt, hesitation, conviction, etc., and to it is related pure general logic in the same way that pure morality, which contains only the necessary moral laws of a free will, is related to practical ethics, which considers these laws under all the impediments of feelings, inclinations, and passions to which men are more or less subjected, and which never can furnish us with a true and demonstrated science, because it, as well as applied logic, requires empirical and psychological principles.
II. Of Transcendental Logic.
General logic, as we have seen, makes abstraction of all content of cognition, that is, of all relation of cognition to its object, and regards only the logical form in the relation of cognitions to each other, that is, the form of thought in general. But as we have both pure and empirical intuitions (as transcendental aesthetic proves), in like manner a distinction might be drawn between pure and empirical thought (of objects). In this case, there would exist a kind of logic, in which we should not make abstraction of all content of cognition; for logic which should comprise merely the laws of pure thought (of an object), would of course exclude all those cognitions which were of empirical content. This kind of logic would also examine the origin of our cognitions of objects, so far as that origin cannot be ascribed to the objects themselves; while, on the contrary, general logic has nothing to do with the origin of our cognitions, but contemplates our representations, be they given primitively a priori in ourselves, or be they only of empirical origin, solely according to the laws which the understanding observes in employing them in the process of thought, in relation to each other. Consequently, general logic treats of the form of the understanding only, which can be applied to representations, from whatever source they may have arisen.
And here I shall make a remark, which the reader must bear well in mind in the course of the following considerations, to wit, that not every cognition a priori, but only those through which we cognize that and how certain representations (intuitions or conceptions) are applied or are possible only a priori; that is to say, the a priori possibility of cognition and the a priori use of it are transcendental. Therefore neither is space, nor any a priori geometrical determination of space, a transcendental representation, but only the knowledge that such a representation is not of empirical origin, and the possibility of its relating to objects of experience, although itself a priori, can be called transcendental. So also, the application of space to objects in general would be transcendental; but if it be limited to objects of sense it is empirical. Thus, the distinction of the transcendental and empirical belongs only to the critique of cognitions, and does not concern the relation of these to their object.
Accordingly, in the expectation that there may perhaps be conceptions which relate a priori to objects, not as pure or sensuous intuitions, but merely as acts of pure thought (which are therefore conceptions, but neither of empirical nor aesthetical origin)— in this expectation, I say, we form to ourselves, by anticipation, the idea of a science of pure understanding and rational cognition, by means of which we may cogitate objects entirely a priori. A science of this kind, which should determine the origin, the extent, and the objective validity of such cognitions, must be called transcendental logic, because it has not, like general logic, to do with the laws of understanding and reason in relation to empirical as well as pure rational cognitions without distinction, but concerns itself with these only in an a priori relation to objects.
III. Of the Division of General Logic into Analytic and Dialectic.
The old question with which people sought to push logicians into a corner, so that they must either have recourse to pitiful sophisms or confess their ignorance, and consequently the vanity of their whole art, is this: “What is truth?” The definition of the word truth, to wit, “the accordance of the cognition with its object,” is presupposed in the question; but we desire to be told, in the answer to it, what is the universal and secure criterion of the truth of every cognition.
To know what questions we may reasonably propose is in itself a strong evidence of sagacity and intelligence. For if a question be in itself absurd and unsusceptible of a rational answer, it is attended with the danger — not to mention the shame that falls upon the person who proposes it — of seducing the unguarded listener into making absurd answers, and we are presented with the ridiculous spectacle of one (as the ancients said) “milking the he-goat, and the other holding a sieve.”
If truth consists in the accordance of a cognition with its object, this object must be, ipso facto, distinguished from all others; for a cognition is false if it does not accord with the object to which it relates, although it contains something which may be affirmed of other objects. Now a universal criterion of truth would be that which is valid for all cognitions, without distinction of their objects. But it is evident that since, in the case of such a criterion, we make abstraction of all the content of a cognition (that is, of all relation to its object), and truth relates precisely to this content, it must be utterly absurd to ask for a mark of the truth of this content of cognition; and that, accordingly, a sufficient, and at the same time universal, test of truth cannot possibly be found. As we have already termed the content of a cognition its matter, we shall say: “Of the truth of our cognitions in respect of their matter, no universal test can be demanded, because such a demand is self-contradictory.”
On the other hand, with regard to our cognition in respect of its mere form (excluding all content), it is equally manifest that logic, in so far as it exhibits the universal and necessary laws of the understanding, must in these very laws present us with criteria of truth. Whatever contradicts these rules is false,