In the essay on the principle of sufficient reason, § 23, I have fully explained the incorrectness of the following proof of the a priori nature and of the necessity of the law of causality from the mere succession of events in time; I must, therefore, content myself here by referring to that passage.[6] This is precisely the case with the proof of reciprocity also, the concept of which I was obliged to explain above as invalid. What is necessary has also been said of modality, the working out of the principles of which now follows.
There are still a few points in the further course of the transcendental analytic which I should have to refute were it not that I am afraid of trying the patience of the reader; I therefore leave them to his own reflection. But ever anew in the “Critique of Pure Reason” we meet that principal and fundamental error of Kant's, which I have copiously denounced above, the complete failure to distinguish abstract, discursive knowledge from intuitive. It is this that throws a constant obscurity over Kant's whole [pg 081] theory of the faculty of knowledge, and never allows the reader to know what he is really speaking about at any time, so that instead of understanding, he always merely conjectures, for he alternately tries to understand what is said as referring to thought and to perception, and remains always in suspense. In the chapter “On the Division of all Objects into Phenomena and Noumena,” Kant carries that incredible want of reflection as to the nature of the idea of perception and the abstract idea, as I shall explain more fully immediately, so far as to make the monstrous assertion that without thought, that is, without abstract conceptions, there is no knowledge of an object; and that perception, because it is not thought, is also not knowledge, and, in general, is nothing but a mere affection of sensibility, mere sensation! Nay, more, that perception without conception is absolutely void; but conception without perception is yet always something (p. 253; V. 309). Now this is exactly the opposite of the truth; for concepts obtain all significance, all content, only from their relation to ideas of perception, from which they have been abstracted, derived, that is, constructed through the omission of all that is unessential: therefore if the foundation of perception is taken away from them, they are empty and void. Perceptions, on the contrary, have in themselves immediate and very great significance (in them, indeed, the thing in itself objectifies itself); they represent themselves, express themselves, have no mere borrowed content like concepts. For the principle of sufficient reason governs them only as the law of causality, and determines as such only their position in space and time; it does not, however, condition their content and their significance, as is the case with concepts, in which it appears as the principle of the ground of knowing. For the rest, it looks as if Kant really wished here to set about distinguishing the idea of perception and the abstract idea. He objects to Leibnitz and Locke that the former reduced everything to abstract ideas, and the latter everything [pg 082] to ideas of perception. But yet he arrives at no distinction; and although Locke and Leibnitz really committed these errors, Kant himself is burdened with a third error which includes them both—the error of having so mixed up knowledge of perception and abstract knowledge that a monstrous hybrid of the two resulted, a chimera of which no distinct idea is possible, and which therefore necessarily only confused and stupefied students, and set them at variance.
Certainly thought and perception are separated more in the chapter referred to “On the Division of all Objects into Phenomena and Noumena” than anywhere else, but the nature of this distinction is here a fundamentally false one. On p. 253; V. 309, it is said: “If I take away all thought (through the categories) from empirical knowledge, there remains absolutely no knowledge of an object, for through mere perception nothing at all is thought, and that this affection of sensibility is in me establishes really no relation of such ideas to any object.” This sentence contains, in some degree, all the errors of Kant in a nutshell; for it brings out clearly that he has falsely conceived the relation between sensation, perception, and thought, and accordingly identifies the perception, whose form he yet supposes to be space, and indeed space in all its three dimensions, with the mere subjective sensation in the organs of sense, but only allows the knowledge of an object to be given through thought, which is different from perception. I, on the contrary, say: Objects are first of all objects of perception, not of thought, and all knowledge of objects is originally and in itself perception. Perception, however, is by no means mere sensation, but the understanding is already active in it. The thought, which is added only in the case of men, not in the case of the brutes, is mere abstraction from perception, gives no fundamentally new knowledge, does not itself establish objects which were not before, but merely changes the form of the knowledge already won through perception, [pg 083] makes it abstract knowledge in concepts, whereby its concrete or perceptible character is lost, but, on the other hand, combination of it becomes possible, which immeasurably extends the range of its applicability. The material of our thought is, on the other hand, nothing else than our perceptions themselves, and not something which the perceptions did not contain, and which was added by the thought; therefore the material of everything that appears in our thought must be capable of verification in our perception, for otherwise it would be an empty thought. Although this material is variously manipulated and transformed by thought, it must yet be capable of being reduced to perception, and the thought traced back to this—just as a piece of gold can be reduced from all its solutions, oxides, sublimates, and combinations, and presented pure and undiminished. This could not happen if thought itself had added something, and, indeed, the principal thing, to the object.
The whole of the chapter on the Amphiboly, which follows this, is merely a criticism of the Leibnitzian philosophy, and as such is on the whole correct, though the form or pattern on which it is constructed is chosen merely for the sake of architectonic symmetry, which here also is the guiding clue. Thus, to carry out the analogy with the Aristotelian Organon, a transcendental Topic is set up, which consists in this, that every conception is to be considered from four points of view, in order to make out to which faculty of knowledge it belongs. But these four points of view are quite arbitrarily selected, and ten others might be added to them with just as much right; but their fourfold number corresponds to the titles of the categories, and therefore the chief doctrine of Leibnitz is divided among them as best it may be. By this critique, also, to some extent, certain errors are stamped as natural to the reason, whereas they were merely false abstractions of Leibnitz's, who, rather than learn from his great philosophical contemporaries, Spinoza and Locke, preferred to [pg 084] serve up his own strange inventions. In the chapter on the Amphiboly of Reflection it is finally said that there may possibly be a kind of perception entirely different from ours, to which, however, our categories are applicable; therefore the objects of that supposed perception would be noumena, things which can only be thought by us; but since the perception which would give that thought meaning is wanting to us, and indeed is altogether quite problematical, the object of that thought would also merely be a wholly indefinite possibility. I have shown above by quotations that Kant, in utter contradiction with himself, sets up the categories now as the condition of knowledge of perception, now as the function of merely abstract thought. Here they appear exclusively in the latter sense, and it seems quite as if he wished to attribute them merely to discursive thought. But if this is really his opinion, then necessarily at the beginning of the Transcendental Logic, before specifying the different functions of thought at such length, he was necessarily bound to characterise thought in general, and consequently to distinguish it from perception; he ought to have shown what knowledge is given by mere perception, and what that is new is added by thought. Then we would have known what he was really speaking about; or rather, he would then have spoken quite differently, first of perception, and then of thought; instead of which, as it is, he is always dealing with something between the two, which is a mere delusion. There would not then be that great gap between the transcendental Æsthetic and the transcendental Logic, where, after the exposition of the mere form of perception, he simply dismisses its content, all that is empirically apprehended, with the phrase “It is given,” and does not ask how it came about, whether with or without understanding; but, with one spring, passes over to abstract thought; and not even to thought in general, but at once to certain forms of thought, and does not say a word about what thought is, what the concept is, what is the relation of abstract and [pg 085] discursive to concrete and intuitive, what is the difference between the knowledge of men and that of brutes, and what is reason.
Yet it was just this distinction between abstract knowledge and knowledge of perception, entirely overlooked by Kant, which the ancients denoted by φαινομενα and νοουμενα,[7] and whose opposition and incommensurability occupied them so much in the philosophemes of the Eleatics, in Plato's doctrine of Ideas, in the dialectic of the Megarics, and later the Scholastics in the controversy between Nominalism and Realism, the seed of which, so late in developing, was already contained in the opposite mental tendencies of Plato and Aristotle. But Kant, who, in an inexcusable manner, entirely neglected the thing to denote which the words φαινομενα and νοουμενα had already been taken, took possession of the words, as if they were still unappropriated, in order to denote by them his thing in itself and his phenomenon.
Since I have been obliged to reject Kant's doctrine of the categories, just as he rejected that of Aristotle, I wish here to indicate as a suggestion a third way of reaching what is aimed at. What both Kant and Aristotle sought for under the name of the categories were the most general conceptions under which all things, however different, must be subsumed, and through which therefore everything that exists would ultimately be thought. Just on this account Kant conceived them as the forms of all thought.
Grammar is related to logic as clothes to the body. Should not, therefore, these primary conceptions, the ground-bass of the reason, which is the foundation of all special thought, without whose application, therefore, no thought can take place, ultimately lie in those conceptions which [pg 086] just on account of their exceeding generality (transcendentalism) have their expression not in single words, but in whole classes of words, because one of them is thought along with every word whatever it may be, whose designation would therefore have to be looked for, not in the lexicon but in the grammar? In fact, should they not be those distinctions of conceptions on account of which the word which expresses them is either a substantive or an adjective, a verb or an adverb, a pronoun, a preposition, or some other particle—in short, the parts of speech? For undoubtedly these denote the forms which all thought primarily assumes, and in which it directly moves; accordingly they are the essential forms of speech, the fundamental constituent elements of every language, so that we cannot imagine any language which would not consist of at least substantives, adjectives, and verbs. These fundamental forms would then have subordinated to them those forms of thought which are expressed through their inflections, that is, through declension and conjugation, and it is unessential to the chief concern whether in denoting them we call in the assistance of the article and the pronoun. We will examine the thing, however, somewhat more closely, and ask the question anew: What are the forms of thought?
(1.) Thought consists throughout of judging; judgments are the threads of its whole web, for without making use of a verb our thought does not move, and as often as we use a verb we judge.
(2.) Every judgment consists in the recognition of the relation between subject and predicate, which it separates or unites with various restrictions. It unites them from the recognition of the actual identity of the two, which can only happen in the case of synonyms; then in the recognition that the one is always thought along with the other, though the converse does not hold—in the universal affirmative proposition; up to the recognition that the one is sometimes thought along with the other, in the [pg 087] particular affirmative proposition. The negative propositions take the opposite course. Accordingly in every judgment the subject, the predicate, and the copula, the latter affirmative or negative, must be to be found; even although each of these is not denoted by a word of its own, as is however generally the case. The predicate and the copula are often denoted by one word, as “Caius ages;” sometimes one word denotes all three, as concurritur, i.e., “the armies engage.” From this it is evident that the forms of thought are not to be sought for precisely and directly in words, nor even in the parts of speech, for even in the same language the same judgment may be expressed in different words, and indeed in different parts of speech, yet the thought remains the same, and consequently also its form; for the thought could not be the same if the form of thought itself were different. But with the same thought and the same form of thought the form of words may very well be different, for it is merely the outward clothing of the thought, which, on the other hand, is inseparable from its form. Thus grammar only explains the clothing of the forms of thought. The parts of speech can therefore be deduced from the original forms of thought themselves which are independent of all language; their work is to express these forms of thought in all their modifications. They are the instrument and the clothing of the forms of thought, and must be accurately adapted to the structure of the latter, so that it may be recognised in them.