Critique of Pure Reason

by Immanuel Kant

  But although, when dealing with the purely speculative questions of pure reason, no hypotheses are admissible in order to found on them any propositions, they are perfectly admissible in order, if possible, to defend them; that is to say, they may be used for polemical, but not for dogmatical purposes. Nor do I understand by defending the strengthening of the proofs in support of our assertions, but only the refutation of the dialectical arguments of the opponent which are intended to invalidate our assertions. All synthetical propositions of pure reason have this peculiarity that, although the philosopher who maintains the reality of certain ideas never possesses sufficient knowledge in order to render his own propositions certain, his opponent is equally unable to prove the opposite. It is true, no doubt, that this equality of fortune, which is peculiar to human reason, favours neither of the two parties with regard to their speculative knowledge, and hence the never-ending feuds in this arena. But we shall see nevertheless that, in relation to its practical employment, reason has the right of admitting what, in the sphere of pure speculation, it would not be allowed to admit without sufficient proof. Such admissions, no doubt, detract from the perfection of speculation, but practical interests take no account of this. Here, therefore, reason is in possession, without having to prove the legitimacy of its title, which, indeed, it would be difficult to do. The burden of proof rests, therefore, on the opponent; and as he knows as little of the point in question, to enable him to prove its non-existence, as the other who maintains its reality, it is evident that there is an advantage on the side of him who maintains something as a practically necessary supposition (melior est conditio possidentis). He is clearly entitled, as it were in self-defence, to use the same weapons in support of his own good cause, which the opponent uses against it, that is, to employ hypotheses, which are not intended to strengthen the arguments in favour of his own view, but only to show that the opponent knows far too little of the subject under discussion to flatter himself that he possesses any advantage over us, so far as speculative insight is concerned.

  In the field of pure reason, therefore, hypotheses are admitted as weapons of defence only, not in order to establish a right, but simply in order to defend it; and it is our duty at all times to look for a real opponent within ourselves. Speculative reason in its transcendental employment is by its very nature dialectical. The objections which we have to fear lie in ourselves. We must look for them as we look for old, but never superannuated claims, if we wish to destroy them, and thus to establish a permanent peace. External tranquillity is a mere illusion. It is necessary to root up the very germ of these objections which lies in the nature of human reason; and how can we root it up, unless we allow it freedom, nay, offer it nourishment, so that it may send out shoots, and thus discover itself to our eyes, so that we may afterwards destroy it with its very root? Try yourselves therefore to discover objections of which no opponent has ever thought; nay, lend him your weapons, and grant him the most favourable position which he could wish for. You have nothing to fear in all this, but much to hope for, namely, that you may gain a possession which no one will ever again venture to contest.

  In order to be completely equipped you require the hypotheses of pure reason also, which, although but leaden weapons (because not steeled by any law of experience), are yet quite as strong as those which any opponent is likely to use against you. If, therefore (for any not speculative reason), you have admitted the immaterial nature of the soul, which is not subject to any corporeal changes, and you are met by the difficulty that nevertheless experience seems to prove both the elevation and the decay of our mental faculties as different modifications of our organs, you can weaken the force of this objection by saying that you look upon the body as a fundamental phenomenon only, which, in our present state (in this life), forms the condition of all the faculties of our sensibility, and hence of our thought. In that case the separation from the body would be the end of the sensuous employment and the beginning of the intelligible employment of our faculty of knowledge. The body would thus have to be considered, not as the cause of our thinking, but only as a restrictive condition of it, and, therefore, if on one side as a support of our sensuous and animal life, on the other, all the more, as an impediment of our pure and spiritual life, so that the dependence of the animal life on the constitution of the body would in no wise prove the dependence of our whole life on the state of our organs. You may go even further and discover new doubts which have either not been raised at all before, or at all events have not been carried far enough.

  Generation in the human race, as well as among irrational creatures, depends on so many accidents, on occasion, on sufficient sustenance, on the views and whims of government, nay, even on vice, that it is difficult to believe in the eternal existence of a being whose life has first begun under circumstances so trivial, and so entirely dependent on our own choice. As regards the continuance (here on earth) of the whole race, there is less difficulty, because the accidents in individual cases are subject nevertheless to a rule with regard to the whole. With regard to each individual, however, to expect so important an effect from such insignificant causes seems very strange. But even against this you may adduce the following transcendental hypothesis, namely, that all life is really intelligible only, not subject to the changes of time, and neither beginning in birth, nor ending in death. You may say that this life is phenomenal only, that is, a sensuous representation of the pure spiritual life, and that the whole world of sense is but an image passing before our present mode of knowledge, but, like a dream, without any objective reality in itself; nay, that if we could see ourselves and other objects also as they really are, we should see ourselves in a world of spiritual natures, our community with which did neither begin at our birth nor will end with the death of the body, both being purely phenomenal.

  Although it is true that we do not know anything about what we have here been pleading hypothetically against our opponents, and that we ourselves do not even seriously maintain it, it being simply an idea invented for self-defence and not even an idea of reason, yet we are acting throughout quite rationally. In answer to our opponent who imagines that he has exhausted all possibilities, and who wrongly represents the absence of empirical conditions as a proof of the total impossibility of our own belief, we are simply showing him that he can no more, by mere laws of experience, comprehend the whole field of possible things by themselves than we are able, outside of experience, to establish anything for our reason on a really secure foundation. Because we bring forward such hypothetical defences against the pretensions of our boldly denying opponent, we must not be supposed to have adopted these opinions as our own. We abandon them so soon as we have disposed of the dogmatical conceit of our opponent. It seems no doubt very modest and moderate to maintain a simple negative position with regard to the assertions of other people; but to attempt to represent objections as proofs of the opposite opinion is quite as arrogant as to assume the position of the affirming party and its opinions.

  It is easy to see, therefore, that in the speculative employment of reason hypotheses are of no value by themselves, but relatively only, as opposed to the transcendental pretensions of the opposite party. For to extend the principles of possible experience to the possibility of things in general is quite as transcendent as to ascribe objective reality to concepts which cannot have an object except outside the limits of all possible experience. The assertory judgments of pure reason must (like everything known by reason) be either necessary or nothing at all. Reason, in fact, knows of no opinions. The hypotheses, however, which we have just been discussing are problematical judgments only, which, at least, cannot be refuted, though they can neither be proved by anything. They are nothing but private5 opinions, but (for our own satisfaction) we cannot well do without them to counteract misgivings that may arise in our minds. In this character they should be maintained, but we must take great care less they should assume independent authority and a certain absolute validity, and drown
our reason beneath fictions and phantoms.

  The Discipline of Pure Reason

  Section IV

  The Discipline of Pure Reason with Regard to its Proofs

  What distinguishes the proofs of transcendental and synthetical propositions from all other proofs of a synthetical knowledge a priori is this, that reason is not allowed here to apply itself directly to an object through its concepts, but has first to prove the objective validity of those concepts and the possibility of their synthesis a priori. This rule is not suggested by prudence only, but refers to the very nature and the possibility of such proofs. If I am to go beyond the concept of an object a priori, this is impossible without some special guidance coming to me from without that concept. In mathematics it is intuition a priori which thus guides my synthesis, so that all our conclusions may be drawn immediately from pure intuition. In transcendental knowledge the same guidance, so long as we are dealing with concepts of the understanding only, is to be found in possible experience. For here the proof does not show that the given concept (for instance, the concept of that which happens) leads directly to another concept (that of a cause). This would be a saltus which nothing could justify. What our proof really shows is, that experience itself and therefore the object of experience would be impossible without such a (causal) connection. The proof, therefore, had at the same time to indicate the possibility of arriving synthetically and a priori at a certain knowledge of things which was not contained in our concept of them. Unless we attend to this point, our proofs, like streams which have broken their banks, run wildly across the fields wherever the inclination of some hidden association may chance to lead them. The semblance of a conviction, based on subjective causes of association and mistaken for the perception of a natural affinity, cannot balance the misgivings which are justly roused by such bold proceedings. Hence all attempts at proving the principle of sufficient reason have, according to the universal admission of all competent judges, been vain; and before the appearance of transcendental criticism it was thought better, as that principle could never be surrendered, to make a sturdy appeal to the common sense of mankind (an expedient which always shows that the cause of reason is desperate) than to attempt new dogmatical proofs of it.

  But, if the proposition that has to be proved is an assertion of pure reason, and if I even intend by means of pure ideas to go beyond my empirical concepts, it would be all the more necessary that the proof should contain the justification of such a step of synthesis (if it were possible) as a necessary condition of its own validity. The so-called proof of the simple nature of our thinking substance (soul), derived from the unity of apperception, seems very plausible; but it is confronted by an inevitable difficulty, because, as the absolute unity is not a concept that can be immediately referred to a perception, but, as an idea, can only be inferred, it is difficult to understand how the mere consciousness which is, or at least may be, contained in all thought, though it may be so far a simple representation, can lead me on to the consciousness and the knowledge of a thing, in which thought alone is contained. For if I represent to myself the power of my body, as in motion, it is then to me an absolute unity, and my representation of it is a simple one. I can, therefore, very well express this representation by the motion of a point; because the volume of the body is here of no consequence, and can, without any diminution of its power, be conceived as small as one likes, and, therefore, even as existing in one point. But I should never conclude from this that, if nothing is given to me but the motive power of a body, that body can be conceived as a simple substance, because its representation is independent of the quantity of its volume, and, therefore, simple. I thus detect a paralogism, because the simple in the abstract is totally different from the simple as an object, and the ego which, conceived in the abstract, contains nothing manifold, can, as an object, when signifying the soul, become a very complex concept, comprehending and implying many things. In order to be prepared for such a paralogism (for unless we suspected it, the proof might excite no suspicion), it is absolutely necessary to be always in possession of a criterion of such synthetical propositions, which are meant to prove more than experience can ever supply. This criterion consists in our demanding that the proof should not be carried directly to the predicate in question, but that, first, the principle of the possibility of expanding our given concept a priori into ideas and realising them, should be established. If we always exercised this caution, and, before attempting any such proof, wisely considered ourselves, how, and with what degree of confidence, we might expect such an expansion through pure reason, and whence we might take, in such cases, knowledge which cannot be evolved from concepts nor anticipated with reference to possible experience, we might spare ourselves many difficult, and yet fruitless endeavours, by not asking of reason what evidently is beyond its power, or rather, by subjecting reason, which when once under the influence of this passion for speculative conquest, is not easily checked, to a thorough discipline of moderation.

  The first rule, therefore, is to attempt no transcendental proofs before having first considered from whence we should take the principles on which such proofs are to be based, and by what right we may expect our conclusions to be successful. If they are principles of the understanding (for instance of causality), it is useless to attempt to arrive, by means of them, at ideas of pure reason; because they are valid only with regard to objects of experience. If they are principles of pure reason, it is again labour lost, because, though reason possesses such principles, they are all, as objective principles, dialectical and cannot be valid, except perhaps as regulative principles, for the empirical use of reason, in order to make it systematically coherent. If such so-called proofs exist already, we ought to meet their deceptive pleadings with the non liquet of a mature judgment; and although we may be unable to expose their sophisms, we have a perfect right to demand a deduction of the principles employed, which, if these principles are to have their origin in reason alone, will never be forthcoming. You may thus dispense with the analysis and refutation of every one of these sophisms, and dispose in a lump of the endless fallacies of Dialectic, by appealing to the tribunal of critical reason, which insists on laws.

  The second peculiarity of transcendental proofs is this, that for every transcendental proposition one proof only can be found. If I have to draw conclusions, not from concepts, but from the intuition which corresponds to a concept, whether it be pure intuition, as in mathematics, or empirical, as in physical science, the intuition on which my conclusions are to rest supplies me with manifold material for synthetical propositions, which I may connect in more than one way, so that, by starting from different points, I can arrive at the same conclusion by different paths.

  Every transcendental proposition, on the contrary, starts from one concept only, and predicates the synthetical condition of the possibility of the object, according to that concept. There can therefore be but one proof, because beside that concept there is nothing else whereby that object could be determined. The proof therefore can contain nothing more but the determination of an object in general according to that concept, which is itself one only. In the transcendental Analytic, for instance, we had deduced the principle, that everything which happens has a cause, from the single condition of the objective possibility of the concept of an event in general, namely, that the determination of any event in time, and therefore the event itself also, as belonging to experience, would be impossible, unless it were subject to such a dynamical rule. This is therefore the only possible proof; for the event which we represent to ourselves has objective validity, that is, truth, on this condition only, that an object is determined as belonging to that concept by means of the law of causality. It is true that other arguments in support of this proposition have been attempted, for instance, one derived from contingency; but if that argument is examined more carefully, we can discover no characteristic sign of contingency, except the happening, that is, existence preceded by the non-existence of the obj
ect, which leads us back to the same argument as before. If the proposition has to be proved that everything which thinks is simple, no attention is paid to what is manifold in thought, and the concept of the ego only is kept in view, which is simple, and to which all thinking is referred. The same applies to the transcendental proof of the existence of God, which rests entirely on the reciprocability of the two concepts of a most real and a necessary Being, and cannot be found anywhere else.

  By this caution the criticism of the assertions of reason is much simplified. Wherever reason operates with concepts only, only one proof is possible, if any. If therefore we see the dogmatist advance with his ten proofs, we may be sure that he has none. For if he had one which (as it ought to be in all matters of pure reason) had apodictic power, what need would he have of others? His object can only be the same as that of the parliamentary lawyer who has one argument for one person, and another for another. He wants to take advantage of the weakness of the judges, who, without enquiring more deeply, and in order to get away as soon as possible, lay hold of the first argument that catches their attention, and decide accordingly.

  The third peculiar rule of pure reason, if it is once subjected to a proper discipline with regard to transcendental proofs, is this, that such proofs must never be apagogical or circumstantial, but always ostensive or direct. The direct or ostensive proof combines, with regard to every kind of knowledge, a conviction of its truth with an insight into its sources; the apagogical proof, on the contrary, though it may produce certainty, cannot help us to comprehend the truth in its connection with the grounds of its possibility. It is therefore a mere expedient, and cannot satisfy all the requirements of reason. The apagogical proofs have, however, this advantage with regard to their evidence over direct proofs, that contradiction always carries with it more clearness in the representation than the best combination, and thus approaches more to the intuitional character of a demonstration.