Critique of Pure Reason

by Immanuel Kant

  III. Of Demonstrations. An apodictic proof only, so far as it is intuitive, can be called demonstration. Experience may teach us what is, but never that it cannot be otherwise. Empirical arguments, therefore, cannot produce an apodictic proof. From concepts a priori, however (in discursive knowledge), it is impossible that intuitive certainty, that is, evidence, should ever arise, however apodictically certain the judgment may otherwise seem to be. Demonstrations we get in mathematics only, because here our knowledge is derived not from concepts, but from their construction, that is, from intuition, which can be given a priori, in accordance with the concepts. Even the proceeding of algebra, with its equations, from which by reduction both the correct result and its proof are produced, is a construction by characters, though not geometrical, in which, by means of signs, the concepts, particularly those of the relation of quantities, are represented in intuition, and (without any regard to the heuristic method) all conclusions are secured against errors by submitting each of them to intuitive evidence. Philosophical knowledge cannot claim this advantage, for here we must always consider the general in the abstract (by concepts), while in mathematics we may consider the general in the concrete, in each single intuition, and yet through pure representation a priori, where every mistake becomes at once manifest. I should prefer, therefore, to call the former acroamatic, or audible (discursive) proofs, because they can be carried out by words only (the object in thought), rather than demonstrations, which, as the very term implies, depend on the intuition of the object.

  It follows from all this that it is not in accordance with the very nature of philosophy to boast of its dogmatical character, particularly in the field of pure reason, and to deck itself with the titles and ribands of mathematics, an order to which it can never belong, though it may well hope for co-operation with that science. All those attempts are vain pretensions which can never be successful, nay, which can only prove an obstacle in the discovery of the illusions of reason, when ignoring its own limits, and which must mar our success in calling back, by means of a sufficient explanation of our concepts, the conceit of speculation to the more modest and thorough work of self-knowledge. Reason ought not, therefore, in its transcendental endeavours, to look forward with such confidence, as if the path which it has traversed must lead straight to its goal, nor depend with such assurance on its premisses as to consider it unnecessary to look back from time to time, to find out whether, in the progress of its conclusions, errors may come to light, which were overlooked in the principles, and which render it necessary either to determine those principles more accurately or to change them altogether.

  I divide all apodictic propositions, whether demonstrable or immediately certain, into Dogmata and Mathemata. A directly synthetical proposition, based on concepts, is a Dogma; a proposition of the same kind, arrived at by the construction of concepts, is a Mathema. Analytical judgments teach us really no more of an object than what the concept which we have of it contains in itself. They cannot enlarge our knowledge beyond the concept, but only clear it. They cannot, therefore, be properly called dogmas (a word which might perhaps best be translated by precepts, Lehrsprüche). According to our ordinary mode of speech, we could apply that name to that class only of the two above-mentioned classes of synthetical propositions a priori which refers to philosophical knowledge, and no one would feel inclined to give the name of Dogma to the propositions of arithmetic or geometry. In this way the usage of language confirms our explanation that those judgments only which are based on conceptions, and not those which are arrived at by the construction of concepts, can be called dogmatic.

  Now in the whole domain of pure reason, in its purely speculative use, there does not exist a single directly synthetical judgment based on concepts. We have shown that reason, by means of ideas, is incapable of any synthetical judgments which could claim objective validity, while by means of the concepts of our understanding it establishes no doubt some perfectly certain principles, but not directly from concepts, but indirectly only, by referring such concepts to something purely contingent, namely, possible experience. When such experience (anything as an object of possible experience) is presupposed, these principles are, no doubt, apodictically certain, but in themselves (directly) they cannot even be known a priori. Thus the proposition that everything which happens has its cause, can never be thoroughly understood by means of the concepts alone which are contained in it; hence it is no dogma in itself, although, from another point of view, that is, in the only field of its possible use, namely, in experience, it may be proved apodictically. It should be called, therefore, a principle, and not a precept or a dogma (though it is necessary that it should itself be proved), because it has this peculiarity that it first renders its own proof, namely, experience, possible, and has always to be presupposed for the sake of experience.

  If, therefore, there are no dogmata whatever in the speculative use of pure reason, with regard to their contents also, all dogmatical methods, whether borrowed from mathematics or invented on purpose, are alike inappropriate. They only serve to hide mistakes and errors, and thus deceive philosophy, whose true object is to shed the clearest light on every step which reason takes. The method may, however, well be systematical; for our reason (subjectively) is itself a system, though in its pure use, by means of mere concepts, a system intended for investigation only, according to principles of unity, to which experience alone can supply the material. We cannot, however, dwell here on the method of transcendental philosophy, because all we have to do at present is to take stock in order to find out whether we are able to build at all, and how high the edifice may be which we can erect with the materials at our command (the pure concepts a priori).

  Method of Transcendentalism

  Section II

  The Discipline of Pure Reason in its Polemical Use

  Reason in all her undertakings must submit to criticism, and cannot attempt to limit the free exercise of such criticism without injury to herself, and without exposing herself to dangerous suspicion. There is nothing so important with reference to its usefulness, nothing so sacred, that it could withdraw itself from that searching examination which has no respect of persons. The very existence of reason depends on that freedom; for reason can claim no dictatorial authority, but its decrees are rather like the votes of free citizens, every one of whom may freely express, not only his doubts, but even his veto.

  But, though reason can never refuse to submit to criticism, it does not follow that she need always be afraid of it, while pure reason in her dogmatical (not mathematical) use is not so thoroughly conscious of having herself obeyed her own supreme laws as not to appear with a certain shyness, nay, without any of her assumed dogmatical authority, before the tribunal of a higher judicial reason.

  The case is totally different when reason has to deal, not with the verdicts of a judge, but with the claims of her fellow-citizens, and has to defend itself only against these claims. For as these mean to be as dogmatical in their negations as reason is in her affirmations, reason may justify herself , so as to be safe against all damages, and with a good title to her own property that need not fear any foreign claims, although it could not itself be established with sufficient evidence.

  By the polemical use of pure reason I mean the defence of her own propositions against dogmatical negations. Here the question is not, whether her own assertions may not themselves be false, but it is only to be shown that no one is ever able to prove the opposite with apodictic certainty, nay, even with a higher degree of plausibility. For we are not on sufferance in our possession, when, though our own title may not be sufficient, it is nevertheless quite certain that no one can ever prove its insufficiency.

  It is sad, no doubt, and discouraging, that there should be an antithetic of pure reason, and that reason, being the highest tribunal for all conflicts, should be in conflict with herself. We had on a former occasion to treat of such an apparent antithetic, but we saw that it arose from a misunderstanding, phen
omena, according to the common prejudice, being taken for things in themselves, and an absolute completeness of their synthesis being demanded in one way or other (being equally impossible in either way), a demand entirely unreasonable with regard to phenomena. There was, therefore, no real contradiction in reason herself when making the two propositions, first, that the series of phenomena given by themselves has an absolutely first beginning; and, secondly, that the series is absolutely and by itself without any beginning; for both propositions are perfectly consistent with each other, because phenomena, with regard to their existence as phenomena, are by themselves nothing, that is, something self-contradictory, so that their hypothesis must naturally lead to contradictory inferences.

  We cannot, however, appeal to a similar misunderstanding, in order to remove the conflict of reason, when it is said, for instance, on one side, theistically, that there is a Supreme Being, and on the other, atheistically, that there is no Supreme Being; or if in psychology it is maintained that everything which thinks possesses an absolute and permanent unity and is different, therefore, from all perishable material unity, while others maintain that a soul is not an immaterial unity, and not exempt, therefore from perishableness. For here the object of the question is free from anything heterogeneous or contradictory to its own nature, and our understanding has to deal with things by themselves only and not with phenomena. Here, therefore, we should have a real conflict, if only on the negative side pure reason could advance anything like the ground of an assertion. We may well admit the criticism of the arguments advanced by those who dogmatically assert, without therefore having to surrender these assertions, which are supported at least by the interest of reason, to which the opposite party cannot appeal.

  I cannot share the opinion so frequently expressed by excellent and thoughtful men (for instance Sulzer) who, being fully conscious of the weakness of the proofs hitherto advanced, indulge in a hope that the future would supply us with evident demonstrations of the two cardinal propositions of pure reason, namely, that there is a God, and that there is a future life. I am certain, on the contrary, that this will never be the case, for whence should reason take the grounds for such synthetical assertions, which do not refer to objects of experience and their internal possibility? But there is the same apodictic certainty that no man will ever arise to assert the contrary with the smallest plausibility, much less dogmatically. For, as he could prove it by means of pure reason only, he would have to prove that a Supreme Being, and that a thinking subject within us, as pure intelligence, is impossible. But whence will he take the knowledge that would justify him in thus judging synthetically on things far beyond all possible experience? We may, therefore, rest so completely assured that no one will ever really prove the opposite, that there is no need to invent any scholastic arguments. We may safely accept those propositions which agree so well with the speculative interests of our reason in its empirical use, and are besides the only means of reconciling them with our practical interests. As against our opponent, who must not be considered here as a critic only, we are always ready with our Non liquet. This must inevitably confound our adversary, while we need not mind his retort, because we can always fall back on the subjective maxim of reason, which our adversary cannot, and can thus, protected by it, look upon all his vain attacks with calmness and indifference.

  Thus we see that there is really no antithetic of pure reason, for the only arena for it would be the field of pure theology and psychology, and on that field it is not able to support a champion in full armour and with weapons which we need be afraid of. He can only use ridicule and boasting, and these we may laugh at as mere child's play. This ought to be a real comfort and inspire reason with new courage; for what else could she depend on, if she herself, who is called upon to remove all errors, were divided against herself, without any hope of. peace and quiet possession?

  Whatever has been ordained by nature is good for some purpose or other. Even poisons serve to counteract other poisons which are in our own blood, and they must not be absent therefore in a complete collection of medicines. The objections against the vain persuasions and the conceit of our own purely speculative reason are inspired by the very nature of that reason, and must therefore have their own good purpose, which must not be lightly cast aside. Why has Providence placed certain things, which concern our highest interests, so far beyond our reach that we are only able to apprehend them very indistinctly and dubiously, and our enquiring gaze is more excited than satisfied by them? It is very doubtful whether it is useful to venture on any bold answers with regard to such obscure questions, nay, whether it may not be detrimental. But one thing is quite certain, namely, that it is useful to grant to reason the fullest freedom, both of enquiry and of criticism, so that she may consult her own interest without let or hindrance. And this is done quite as much by limiting her insight as by enlarging it, while nothing but mischief must arise from any foreign interference or any attempt to direct reason, against her own natural inclination, towards objects forced upon her from without.

  Allow, therefore, your adversary to speak reason, and combat him with weapons of reason only. As to any practical interests you need not be afraid, for in purely speculative discussions they are not involved at all. What comes to light in these discussions is only a certain antinomy of reason which, as it springs from the very nature of reason, must needs be listened to and examined. Reason is thus improved only by a consideration of both sides of her subject. Her judgment is corrected by the very limitations imposed upon her. What people may differ about is not the matter so much as the tone and manner of these discussions. For, though you have to surrender the language of knowledge, it is perfectly open to you to retain the language of the firmest faith, which need not fear the severest test of reason.

  If we could ask that dispassionate philosopher, David Hume, who seemed made to maintain the most perfect equilibrium of judgment, what induced him to undermine by carefully elaborated arguments the persuasion, so useful and so full of comfort for mankind, as that reason is sufficient to assert and to form a definite concept of a Supreme Being, he would answer, Nothing but a wish to advance reason in self-knowledge, and at the same time a certain feeling of indignation at the violence which people wish to inflict on reason by boasting of her powers, and yet at the same time preventing her from openly confessing her weakness of which she has become conscious by her own self-examination. If, on the contrary, you were to ask Priestley, who was guided by the principles of the empirical use of reason only and opposed to all transcendental speculation, what could have induced him to pull down two such pillars of religion as the freedom and immortality of our soul (for the hope of a future life is with him an expectation only of the miracle of a resuscitation), he, who was himself so pious and zealous a teacher of religion, could answer nothing but that he was concerned for reason, which must suffer if certain subjects are withdrawn from the laws of material nature, the only laws which we can accurately know and fix. It would be most unjust to decry the latter, who was able to combine his paradoxical assertions with the interests of religion, and to inflict pain on a well-intentioned man, simply because he could not find his way, the moment he strayed away from the field of natural science. And the same favour must be extended to the equally well-intentioned, and in his moral character quite blameless, Hume, who could not and would not leave his abstract speculations, because he was rightly convinced that their object lies entirely outside the limits of natural science, and within the sphere of pure ideas.

  What then is to be done, especially with regard to the danger which is believed to threaten the commonwealth from such speculations? Nothing is more natural, nothing more fair than the decision which you have to come to. Let these people go! If they show talent, if they produce new and profound investigations, in one word, if they show reason, reason can only gain. If you have recourse to anything else but untrammelled reason, if you raise the cry of high treason, and call together the ignorant mob as it we
re to extinguish a conflagration—you simply render yourself ridiculous. For here the question is not what may be useful or dangerous to the commonwealth, but merely how far reason may advance in her speculations, which are independent of all practical interests; in fact, whether these speculations are to count for anything, or are to be surrendered entirely for practical considerations. Instead of rushing in, sword in hand, it is far wiser to watch the struggle from the safe seat of the critic. That struggle is very hard for the combatants themselves, while to you it need not be anything but entertaining, and, as the issue is sure to be without bloodshed, it may become highly improving to your own intellect. For it is extremely absurd to expect to be enlightened by reason, and yet to prescribe to her beforehand on which side she must incline. Besides, reason is naturally so subdued and checked by reason, that you need not send out patrols in order to bring the civil law to bear on that party whose victory you fear. In this dialectical war no victory is gained that need disturb your peace of mind.