Critique of Pure Reason

by Immanuel Kant

  In every syllogism I first think a rule (the major) by means of the understanding. I then bring some special knowledge under the condition of the rule (the minor) by means of the faculty of judgment, and I finally determine my knowledge through the predicate of the rule (conclusio), that is, a priori, by means of reason. It is therefore the relation represented by the major proposition, as the rule, between knowledge and its condition, that constitutes the different kinds of syllogism. Syllogisms are therefore threefold, like all judgments, differing from each other in the manner in which they express the relation of knowledge in the understanding, namely, categorical, hypothetical, and disjunctive.

  If, as often happens, the conclusion is put forward as a judgment, in order to see whether it does not follow from other judgments by which a perfectly different object is conceived, I try to find in the understanding the assertion of that conclusion, in order to see whether it does not exist in it, under certain conditions, according to a general rule. If I find such a condition, and if the object of the conclusion can be brought under the given condition, then that conclusion follows from the rule which is valid for other objects of knowledge also. Thus we see that reason, in forming conclusions, tries to reduce the great variety of the knowledge of the understanding to the smallest number of principles (general conditions), and thereby to produce in it the highest unity.

  C. Of the Pure Use of Reason

  The question to which we have at present to give an answer, though a preliminary one only, is this, whether reason can be isolated and thus constitute by itself an independent source of concepts and judgments, which spring from it alone, and through which it has reference to objects, or whether it is only a subordinate faculty for imparting a certain form to any given knowledge, namely, a logical form, a faculty whereby the cognitions of the understanding are arranged among themselves only, and lower rules placed under higher ones (the condition of the latter comprehending in its sphere the condition of the former) so far as all this can be done by their comparison. Variety of rules with unity of principles is a requirement of reason for the purpose of bringing the understanding into perfect agreement with itself, just as the understanding brings the variety of intuition under concepts, and thus imparts to intuition a connected form. Such a principle however prescribes no law to the objects themselves, nor does it contain the ground on which the possibility of knowing and determining objects depends. It is merely a subjective law of economy, applied to the stores of our understanding; having for its purpose, by means of a comparison of concepts, to reduce the general use of them to the smallest possible number, but without giving us a right to demand of the objects themselves such a uniformity as might conduce to the comfort and the extension of our understanding, or to ascribe to that maxim any objective validity. In one word, the question is, whether reason in itself, that is pure reason, contains synthetical principles and rules a priori, and what those principles are?

  The merely formal and logical procedure of reason in syllogisms gives us sufficient hints as to the ground on which the transcendental principle of synthetical knowledge, by means of pure reason, is likely to rest.

  First, a syllogism, as a function of reason, does not refer to intuitions in order to bring them under rules (as the understanding does with its categories), but to concepts and judgments. Although pure reason refers in the end to objects, it has no immediate relation to them and their intuition, but only to the understanding and its judgments, these having a direct relation to the senses and their intuition, and determining their objects. Unity of reason is therefore never the unity of a possible experience, but essentially different from it, as the unity of the understanding. That everything which happens has a cause, is not a principle discovered or prescribed by reason, it only makes the unity of experience possible, and borrows nothing from reason, which without this relation to possible experience could never, from mere concepts, have prescribed such a synthetical unity.

  Secondly. Reason, in its logical employment, looks for the general condition of its judgment (the conclusion), and the syllogism produced by reason is itself nothing but a judgment by means of bringing its condition under a general rule (the major). But as this rule is again liable to the same experiment, reason having to seek, as long as possible, the condition of a condition (by means of a prosyllogism), it is easy to see that it is the peculiar principle of reason (in its logical use) to find for every conditioned knowledge of the understanding the unconditioned, whereby the unity of that knowledge may be completed.

  This logical maxim, however, cannot become a principle of pure reason, unless we admit that, whenever the condition is given, the whole series of conditions, subordinated to one another, a series, which consequently is itself unconditioned, is likewise given (that is, is contained in the object and its connection).

  Such a principle of pure reason, however, is evidently synthetical; for analytically the conditioned refers no doubt to some condition, but not to the unconditioned. From this principle several other synthetical propositions also must arise of which the pure understanding knows nothing; because it has to deal with objects of a possible experience only, the knowledge and synthesis of which are always conditioned. The unconditioned, if it is really to be admitted, has to be especially considered with regard to all the determinations which distinguish it from whatever is conditioned, and will thus supply material for many a synthetical proposition a priori.

  The principles resulting from this highest principle of pure reason will however be transcendent, with regard to all phenomena; that is to say, it will be impossible ever to make any adequate empirical use of such a principle. It will thus be completely different from all principles of the understanding, the use of which is entirely immanent and directed to the possibility of experience only. The task that is now before us in the transcendental Dialectic which has to be developed from sources deeply hidden in the human reason, is this: to discover the correctness or otherwise the falsehood of the principle that the series of conditions (in the synthesis of phenomena, or of objective thought in general) extends to the unconditioned, and what consequences result therefrom with regard to the empirical use of the understanding:—to find out whether there is really such an objectively valid principle of reason, and not only, in place of it, a logical rule which requires us, by ascending to ever higher conditions, to approach their completeness, and thus to bring the highest unity of reason, which is possible to us, into our knowledge: to find out, I say, whether, by some misconception, a mere tendency of reason has not been mistaken for a transcendental principle of pure reason, postulating, without sufficient reflection, absolute completeness in the series of conditions in the objects themselves, and what kind of misconceptions and illusions may in that case have crept into the syllogisms of reason, the major proposition of which has been taken over from pure reason (being perhaps a petitio rather than a postulatum), and which ascend from experience to its conditions. We shall divide it into two parts, of which the first will treat of the transcendent concepts of pure reason, the second of transcendent and dialectical syllogisms.

  1 Sensibility, if subjected to the understanding as the object on which it exercises its function, is the source of real knowledge, but sensibility, if it influences the action of the understanding itself and leads it on to a judgment, is the cause of error.

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  Transcendental Dialectic

  Book I

  Of the Concepts of Pure Reason

  WHATEVER may be thought of the possibility of concepts of pure reason, it is certain that they are not simply obtained by reflection, but by inference. Concepts of the understanding exist a priori, before experience, and for the sake of it, but they contain nothing but the unity of reflection applied to phenomena, so far as they are necessarily intended for a possible empirical consciousness. It is through them alone that knowledge and determination of an object become possible. They are the first to give material for conclusions, and they are
not preceded by any concepts a priori of objects from which they could themselves be deduced. Their objective reality however depends on this, that because they constitute the intellectual form of all experience, it is necessary that their application should always admit of being exhibited in experience.

  The very name, however, of a concept of reason gives a kind of intimation that it is not intended to be limited to experience, because it refers to a kind of knowledge of which every empirical knowledge is a part only (it may be, the whole of possible experience or of its empirical synthesis): and to which all real experience belongs, though it can never fully attain to it. Concepts of reason serve for conceiving or comprehending; concepts of the understanding for understanding (perceptions). If they contain the unconditioned, they refer to something to which all experience may belong, but which itself can never become an object of experience;—something to which reason in its conclusions from experience leads up, and by which it estimates and measures the degree of its own empirical use, but which never forms part of empirical synthesis. If such concepts possess, notwithstanding, objective validity, they may be called conceptus ratiocinati (concepts legitimately formed); if they have only been surreptitiously obtained, by a kind of illusory conclusion, they may be called conceptus ratiocinantes (sophistical concepts). But as this subject can only be fully treated in the chapter on the dialectical conclusions of pure reason, we shall say no more of it now, but shall only, as we gave the name of categories to the pure concepts of the understanding, give a new name to the concepts of pure reason, and call them transcendental ideas, a name that has now to be explained and justified.

  Transcendental Dialectic

  Book I

  First Section

  Of Ideas in General

  In spite of the great wealth of our languages, a thoughtful mind is often at a loss for an expression that should square exactly with its concept; and for want of which he cannot make himself altogether intelligible, either to others or to himself. To coin new words is to arrogate to oneself legislative power in matters of language, a proceeding which seldom succeeds, so that, before taking so desperate a step, it is always advisable to look about, in dead and learned languages, whether they do not contain such a concept and its adequate expression. Even if it should happen that the original meaning of the word had become somewhat uncertain, through carelessness on the part of its authors, it is better nevertheless to determine and fix the meaning which principally belonged to it (even if it should remain doubtful whether it was originally used exactly in that meaning), than to spoil our labour by becoming unintelligible.

  Whenever therefore there exists one single word only for a certain concept, which, in its received meaning, exactly covers that concept, and when it is of great consequence to keep that concept distinct from other related concepts, we ought not to be lavish in using it nor employ it, for the sake of variety only, as a synonyme in the place of others, but carefully preserve its own peculiar meaning, as otherwise it may easily happen that the expression ceases to attract special attention, and loses itself in a crowd of other words of very different import, so that the thought, which that expression alone could have preserved, is lost with it.

  From the way in which Plato uses the term idea, it is easy to see that he meant by it something which not only was never borrowed from the senses, but which even far transcends the concepts of the understanding, with which Aristotle occupied himself, there being nothing in experience corresponding to the ideas. With him the ideas are archetypes of things themselves, not only, like the categories, keys to possible experiences. According to his opinion they flowed out from the highest reason, which however exists no longer in its original state, but has to recall, with difficulty, the old but now very obscure ideas, which it does by means of reminiscence, commonly called philosophy. I shall not enter here on any literary discussions in order to determine the exact meaning which the sublime philosopher himself connected with that expression. I shall only remark, that it is by no means unusual, in ordinary conversations, as well as in written works, that by carefully comparing the thoughts uttered by an author on his own subject, we succeed in understanding him better than he understood himself, because he did not sufficiently define his concept, and thus not only spoke, but sometimes even thought, in opposition to his own intentions.

  Plato knew very well that our faculty of knowledge was filled with a much higher craving than merely to spell out phenomena according to a synthetical unity, and thus to read and understand them as experience. He knew that our reason, if left to itself, tries to soar up to knowledge to which no object that experience may give can ever correspond; but which nevertheless is real, and by no means a mere cobweb of the brain.

  Plato discovered his ideas principally in what is practical,1 that is, in what depends on freedom, which again belongs to a class of knowledge which is a peculiar product of reason. He who would derive the concept of virtue from experience, and would change what at best could only serve as an example or an imperfect illustration, into a type and a source of knowledge (as many have really done), would indeed transform virtue into an equivocal phantom, changing according to times and circumstances, and utterly useless to serve as a rule. Everybody can surely perceive that, when a person is held up to us as a model of virtue, we have always in our own mind the true original with which we compare this so-called model, and estimate it accordingly. The true original is the idea of virtue, in regard to which all possible objects of experience may serve as examples (proofs of the practicability, in a certain degree, of that which is required by the concept of reason), but never as archetypes. That no man can ever act up to the pure idea of virtue does not in the least prove the chimerical nature of that concept; for every judgment as to the moral worth or unworth of actions is possible by means of that idea only, which forms, therefore, the necessary foundation for every approach to moral perfection, however far the impediments inherent in human nature, the extent of which it is difficult to determine, may keep us removed from it.

  The Platonic Republic has been supposed to be a striking example of purely imaginary perfection. It has become a byword, as something that could exist in the brain of an idle thinker only, and Brucker thinks it ridiculous that Plato could have said that no prince could ever govern well, unless he participated in the ideas. We should do better, however, to follow up this thought and endeavour (where that excellent philosopher leaves us without his guidance) to place it in a clearer light by our own efforts, rather than to throw it aside as useless, under the miserable and very dangerous pretext of its impracticability. A constitution founded on the greatest possible human freedom, according to laws which enable the freedom of each individual to exist by the side of the freedom of others (without any regard to the highest possible human happiness, because that must necessarily follow by itself), is, to say the least, a necessary idea, on which not only the first plan of a constitution or a state, but all laws must be based, it being by no means necessary to take account from the beginning of existing impediments, which may owe their origin not so much to human nature itself as to the actual neglect of true ideas in legislation. For nothing can be more mischievous and more unworthy a philosopher than the vulgar appeal to what is called adverse experience, which possibly might never have existed, if at the proper time institutions had been framed according to those ideas, and not according to crude concepts, which, because they were derived from experience only, have marred all good intentions. The more legislation and government are in harmony with that idea, the rarer, no doubt, punishments would become; and it is therefore quite rational to say (as Plato did), that in a perfect state no punishments would be necessary. And though this can never be realized, yet the idea is quite correct which sets up this maximum as an archetype, in order thus to bring our legislative constitutions nearer and nearer to the greatest possible perfection. Which may be the highest degree where human nature must stop, and how wide the chasm may be between the idea and its realisation, no o
ne can or ought to determine, because it is this very freedom that may be able to transcend any limits hitherto assigned to it.

  It is not only, however, where human reason asserts its free causality and ideas become operative agents (with regard to actions and their objects), that is to say, in the sphere of ethics, but also in nature itself, that Plato rightly discovered clear proofs of its origin from ideas. A plant, an animal, the regular plan of the cosmos (most likely therefore the whole order of nature), show clearly that they are possible according to ideas only; and that though no single creature, under the singular conditions of its existence, can fully correspond with the idea of what is most perfect of its kind (as little as any individual man with the idea of humanity, which, for all that, he carries in his mind as the archetype of all his actions), those ideas are nevertheless determined throughout in the highest understanding each by itself as unchangeable, and are in fact the original causes of things, although it can only be said of the whole of them, connected together in the universe, that it is perfectly adequate to the idea. If we make allowance for the exaggerated expression, the effort of the philosopher to ascend from the mere observing and copying of the physical side of nature to an architectonic system of it, teleologically, that is according to ideas, deserves respect and imitation, while with regard to the principles of morality, legislation, and religion, where it is the ideas themselves that make experience of the good possible, though they can never be fully realized in experience, such efforts are of very eminent merit, which those only fail to recognize who attempt to judge it according to empirical rules, the very validity of which, as principles, was meant to be denied by Plato. With regard to nature, it is experience no doubt which supplies us with rules, and is the foundation of all truth: with regard to moral laws, on the contrary, experience is, alas! but the source of illusion; and it is altogether reprehensible to derive or limit the laws of what we ought to do according to our experience of what has been done.