Critique of Pure Reason

by Immanuel Kant

  The principles of modality, however, are not objectively synthetical, because the predicates of possibility, reality, and necessity do not in the least increase the concept of which they are predicated, by adding anything to its representation. But as nevertheless they are synthetical, they are so subjectively only, i.e. they add to the concept of a (real) thing, without predicating anything new, the peculiar faculty of knowledge from which it springs and on. which it depends, so that, if in the understanding the concept is only connected with the formal conditions of experience, its object is called possible; if it is connected with perception (sensation as the material of the senses), and through it determined by the understanding, its object is called real; while, if it is determined through the connection of perceptions, according to concepts, its object is called necessary. The principles of modality therefore predicate nothing of a concept except the act of the faculty of knowledge by which it is produced. In mathematics a postulate means a practical proposition, containing nothing but a synthesis by which we first give an object to ourselves and produce its concept, as if, for instance, we draw a circle with a given line from a given point in the plane. Such a proposition cannot be proved, because the process required for it is the very process by which we first produce the concept of such a figure. We may therefore with the same right postulate the principles of modality, because they never increase23 the concept of a thing, but indicate the manner only in which the concept was joined with our faculty of knowledge.24

  1 The insertion of man, as suggested by Rosenkranz, is impossible.

  2 Here follows in the Second Edition, Supplement XV.

  3 Here follows, in the later Editions, Supplement XVI.

  4 Here follows in the Second Edition, Supplement XVI b.

  5 Kant wrote, etwas—etwas Auffallendes, the second etwas being the adverb. Rosenkranz has left out one etwas, without necessity. It seems necessary, however, to add Überlegung after transcendentalen, as done by Erdmann.

  ⊃2;Anticipiren könne must certainly be added, as suggested by Schopenhauer.

  6 The first and later editions have a priori. The correction is first made in the Seventh Edition, 1828.

  7 The First and Second Editions read 'When two terms of a proposition are given, the third also.'

  8 Read den Erscheinungen.

  9 I read deren, and afterwards der ersteren, though even then the whole passage is very involved. Professor Noiré thinks that dessen may be referred to Gebrauch, and des ersteren to Grundsatz.

  10 See Supplement XVIII.

  11 Read das man.

  12 See Supplement XIX.

  13 Read anzunehmen berechtigt.

  14 The reading of the First Edition is Ursache; Ursachen is a conjecture made by Rosenkranz and approved by others.

  15 It should be remarked that I am not speaking here of the change of certain relations, but of the change of a state. Therefore when a body moves in a uniform way, it does not change its state of movement, but it does so when its motion increases or decreases.

  16 See Supplement XX.

  17 The unity of the universe, in which all phenomena are supposed to be connected, is evidently a mere deduction of the quietly adopted principle of the communion of all substances as coexistent; for if they were isolated, they would not form parts of a whole, and if their connection (the reciprocity of the manifold) were not necessary for the sake of their coexistence, it would be impossible to use the latter, which is a purely ideal relation, as a proof of the former, which is real. We have shown, however, that communion is really the ground of the possibility of an empirical knowledge of coexistence, and that really we can only conclude from this the existence of the former, as its condition.

  18 Here the same as transcendent.

  19 I have adopted Erdmann's conjecture, als solche Begriffe instead of aus solchen Begriffen.

  20 See Supplement XXI.

  21 Insert man before gleichwohl, and leave out können at the end of the sentence.

  22 Read seine Ursache instead of ihre.

  23 No doubt by reality I assert more than by possibility, but not in the thing itself, which can never contain more in its reality than what is contained in its complete possibility. While possibility is only the positing of a thing in reference to the understanding (in its empirical use), reality is, at the same time, a connection of it with perception.

  24 See Supplement XXII.

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  The Transcendental Doctrine of the Faculty of Judgment or Analytic of Principles

  Chapter III

  On the Ground of Distinction of all Subjects Into Phenomena and Noumena

  WE have now not only traversed the whole domain of the pure understanding, and carefully examined each part of it, but we have also measured its extent, and assigned to everything in it its proper place. This domain, however, is an island and enclosed by nature itself within limits that can never be changed. It is the country of truth (a very attractive name), but surrounded by a wide and stormy ocean, the true home of illusion, where many a fog bank and ice that soon melts away tempt us to believe in new lands, while constantly deceiving the adventurous mariner with vain hopes, and involving him in adventures which he can never leave, and yet can never bring to an end. Before we venture ourselves on this sea, in order to explore it on every side, and to find out whether anything is to be hoped for there, it will be useful to glance once more at the map of that country which we are about to leave, and to ask ourselves, first, whether we might not be content with what it contains, nay, whether we must not be content with it, supposing that there is no solid ground anywhere else on which we could settle; secondly, by what title we possess even that domain, and may consider ourselves safe against all hostile claims. Although we have sufficiently answered these questions in the course of the analytic, a summary recapitulation of their solutions may help to strengthen our conviction, by uniting all arguments in one point.

  We have seen that the understanding possesses everything which it draws from itself, without borrowing from experience, for no other purpose but for experience. The principles of the pure understanding, whether constitutive a priori (as the mathematical) or simply relative (as the dynamical), contain nothing but, as it were, the pure schema of possible experience; for that experience derives its unity from that synthetical unity alone which the understanding originally and spontaneously imparts to the synthesis of imagination, with reference to apperception, and to which all phenomena, as data of a possible knowledge, must conform a priori. But although these rules of the understanding are not only true a priori, but the very source of all truth, that is, of the agreement of our knowledge with objects, because containing the conditions of the possibility of experience, as the complete sphere of all knowledge in which objects can be given to us, nevertheless we do not seem to be content with hearing only what is true, but want to know a great deal more. If therefore this critical investigation does not teach us any more than what, even without such subtle researches, we should have practised ourselves in the purely empirical use of the understanding, it would seem as if the advantages derived from it were hardly worth the labour. One might reply that nothing would be more prejudicial to the enlargement of our knowledge than that curiosity which, before entering upon any researches, wishes to know beforehand the advantages likely to accrue from them, though quite unable as yet to form the least conception of such advantages, even though they were placed before our eyes. There is, however, one advantage in this transcendental investigation which can be rendered intelligible, nay, even attractive to the most troublesome and reluctant apprentice, namely this, that the understanding confined to its empirical use only and unconcerned with regard to the sources of its own knowledge, may no doubt fare very well in other respects, but can never determine for itself the limits of its own use and know what is inside or outside its own sphere. It is for that purpose that such profound investigations are required as we have just instituted. If the understanding canno
t decide whether certain questions lie within its own horizon or not, it can never feel certain with regard to its claims and possessions, but must be prepared for many humiliating corrections, when constantly transgressing, as it certainly will, the limits of its own domain, and losing itself in follies and fancies.

  That the understanding cannot make any but an empirical, and never a transcendental, use of all its principles a priori, nay, of all its concepts, is a proposition which, if thoroughly understood, leads indeed to most important consequences. What we call the transcendental use of a concept in any proposition is its being referred to things in general and to things by themselves, while its empirical use refers to phenomena only, that is, to objects of a possible experience. That the latter use alone is admissible will be clear from the following considerations. What is required for every concept is, first, the logical form of a concept (of thought) in general; and, secondly, the possibility of an object to which it refers. Without the latter, it has no sense, and is entirely empty, though it may still contain the logical function by which a concept can be formed out of any data. The only way in which an object can be given to a concept is in intuition, and though a pure intuition is possible a priori and before the object, yet even that pure intuition can receive its object, and with it its objective validity, by an empirical intuition only, of which it is itself nothing but the form. All concepts, therefore, and with them all principles, though they may be possible a priori, refer nevertheless to empirical intuitions, that is, to data of a possible experience. Without this, they can claim no objective validity, but are a mere play, whether of the imagination or of the understanding with their respective representations. Let us take the concepts of mathematics as an example, and, first, with regard to pure intuitions. Although such principles as 'space has three dimensions,' 'between two points there can be only one straight line,' as well as the representation of the object with which that science is occupied, may be produced in the mind a priori, they would have no meaning, if we were not able at all times to show their meaning as applied to phenomena (empirical objects). It is for this reason that an abstract concept is required to be made sensuous, that is, that its corresponding object is required to be shown in intuition, because, without this, the concept (as people say) is without sense, that is, without meaning. Mathematics fulfil this requirement by the construction of the figure, which is a phenomenon present to the senses (although constructed a priori). In the same science the concept of quantity finds its support and sense in number; and this in turn in the fingers, the beads of the abacus, or in strokes and points which can be presented to the eyes. The concept itself was produced a priori, together with all the synthetical principles or formulas which can be derived from such concepts; but their use and their relation to objects can nowhere be found except in experience, of which those concepts contain a priori the (formal) possibility only.

  That this is the case with all categories and with all the principles drawn from them, becomes evident from the fact that we could not define any one of them (really, that is, make conceivable the possibility of their object),1 without at once having recourse to the conditions of sensibility or the form of phenomena, to which, as their only possible objects, these categories must necessarily be restricted, it being impossible, if we take away these conditions, to assign to them any meaning, that is, any relation to an object, or to make it intelligible to ourselves by an example what kind of thing could be intended by such concepts.

  [When representing the table of the categories, we dispensed with the definition of every one of them, because at that time it seemed unnecessary for our purpose, which concerned their synthetical use only, and because entailing responsibilities which we were not bound to incur. This was not a mere excuse, but a very important prudential rule, viz. not to rush into definitions, and to attempt or pretend completeness or precision in the definition of a concept, hen one or other of its characteristic marks is sufficient without a complete enumeration of all that constitute the whole concept. Now, however, we can perceive that this caution had even a deeper ground, namely, that we could not have defined them, even if we had wished;2 for, if we remove all conditions of sensibility, which distinguish them as the concepts of a possible empirical use, and treat them as concepts of things in general (therefore as of transcendental use), nothing remains but to regard the logical function in judgments as the condition of the possibility of the things themselves, without the slightest indication as to where they could have their application and their object, or how they could have any meaning or objective validity in the pure understanding, apart from sensibility.]3

  No one can explain the concept of quantity in general, except, it may be, by saying that it is the determination of an object, by which we may know how many times the one is supposed to exist in it. But this 'how many times' is based on successive repetition, that is on time, and on the synthesis in it of the homogeneous.

  Reality, again, can only be explained in opposition to a negation, if we think of time (as containing all being) being either filled or empty.

  Were I to leave out permanence (which means existence at all times), nothing would remain of my concept of substance but the logical representation of a subject which I think I can realise by imagining something which is a subject only, without being a predicate of anything. But in this case we should not only be ignorant of all conditions under which this logical distinction could belong to anything, but we should be unable to make any use of it or draw any conclusions from it, because no object is thus determined for the use of this concept, and no one can tell whether such a concept has any meaning at all.

  Of the concept of cause also (if I leave out time, in which something follows on something else by rule) I should find no more in the pure category than that it is something which enables us to conclude the existence of something else, so that it would not only be impossible to distinguish cause and effect from each other, but the concept of cause would possess no indication as to how it can be applied to any object, because, in order to form any such conclusion, certain conditions require to be known of which the concept itself tells us nothing. The so-called principle that everything contingent has a cause, comes no doubt before us with great solemnity and self-assumed dignity. But, if I ask what you understand by contingent and you answer, something of which the non-existence is possible, I should be glad to know how you can recognise this possibility of non-existence, if you do not represent to yourselves, in the series of phenomena, some kind of succession, and in it an existence that follows upon non-existence (or vice versa), and consequently a change? To say that the non-existence of a thing is not self-contradictory is but a lame appeal to a logical condition which, though it is necessary for the concept, yet is by no means sufficient for its real possibility. I can perfectly well remove in thought every existing substance, without contradicting myself, but I can by no means conclude from this as to its objective contingency in its existence, that is, the possibility of its non-existence in itself.

  As regards the concept of community, it is easy to see that, as the pure categories of substance and causality admit of no explanation that would determine their object, neither could such an explanation apply to the reciprocal causality in the relation of substances to each other (commercium).

  As to possibility, existence, and necessity, no one has yet been able to explain them, except by a manifest tautology, so long as their definition is to be exclusively drawn from the pure understanding. To substitute the transcendental possibility of things (when an object corresponds to a concept) for the logical possibility of the concept (when the concept does not contradict itself) is a quibble such as could deceive and satisfy the inexperienced only.

  [It seems to be something strange and even illogical4 that there should be a concept which must have a meaning, and yet is incapable of any explanation. But the case of these categories is peculiar, because it is only by means of the general sensuous condition that they can acquire a definit
e meaning, and a reference to any objects. That condition being left out in the pure category, it follows that it can contain nothing but the logical function by which the manifold is brought into a concept. By means of this function, that is, the pure form of the concept, nothing can be known nor distinguished as to the object belonging to it, because the sensuous condition, under which alone objects can belong to it, has been removed. Thus we see that the categories require, besides the pure concept of the understanding, certain determinations of their application to sensibility in general (schemata). Without them, they would not be concepts by which an object can be known and distinguished from other objects, but only so many ways of thinking an object for possible intuitions, and giving to it, according to one of the functions of the understanding, its meaning (certain requisite conditions being given). They are needed to define an object, and cannot therefore be defined themselves. The logical functions of judgments in general, namely, unity and plurality, assertion and negation, subject and predicate, cannot be defined without arguing in a circle, because the definition would itself be a judgment and contain these very functions. The pure categories are nothing but representations of things in general, so far as the manifold in intuition must be thought by one or the other of these functions. Thus, magnitude is the determination which can [only be thought by a judgment possessing quantity (judicium commune); reality, the determination which can only be thought by an affirmative judgment; while substance is that which, in regard to intuition, must be the last subject of all other determinations. With all this it remains perfectly undetermined, what kind of things they may be with regard to which we have to use one rather than another of these functions, so that, without the condition of sensuous intuition, for which they supply the synthesis, the categories have no relation to any definite object, cannot define any object, and consequently have not in themselves the validity of objective concepts.]