(c.) Modality: has really three forms. It determines the quality as necessary, actual, or contingent. It consequently depends also on the copula.
These three forms of thought spring from the laws of thought of contradiction and identity. But from the principle of sufficient reason and the law of excluded middle springs —
(d.) Relation. It only appears if we judge concerning completed judgments, and can only consist in this, that it either asserts the dependence of one judgment upon another (also in the plurality of both), and therefore combines them in the hypothetical proposition; or else asserts that judgments exclude each other, and therefore separates them in the disjunctive proposition. It depends on the copula, which here separates or combines the completed judgments.
The parts of speech and grammatical forms are ways of expressing the three constituent parts of the judgment, the subject, the predicate, and the copula, and also of the possible relations of these; thus of the forms of thought just enumerated, and the fuller determinations and modifications of these. Substantive, adjective, and verb are therefore essential fundamental constituent elements of language in general; therefore they must be found in all languages. Yet it is possible to conceive a language in which adjective and verb would always be fused together, as is sometimes the case in all languages. Provisionally it may be said, for the expression of the subject are intended the substantive, the article, and the pronoun; for the expression of the predicate, the adjective, the adverb, and the preposition; for the expression of the copula, the verb, which, however, with the exception of the verb to be, also contains the predicate. It is the task of the philosophy of grammar to teach the precise mechanism of the expression of the forms of thought, as it is the task of logic to teach the operations with the forms of thought themselves.
Note.– As a warning against a false path and to illustrate the above, I mention S. Stern's “Vorläufige Grundlage zur Sprachphilosophie,” 1835, which is an utterly abortive attempt to construct the categories out of the grammatical forms. He has entirely confused thought with perception, and therefore, instead of the categories of thought, he has tried to deduce the supposed categories of perception from the grammatical forms, and consequently has placed the grammatical forms in direct relation to perception. He is involved in the great error that language is immediately related to perception, instead of being directly related only to thought as such, thus to the abstract concepts, and only by means of these to perception, to which they, however, have a relation which introduces an entire change of the form. What exists in perception, thus also the relations which proceed from time and space, certainly becomes an object of thought; thus there must also be forms of speech to express it, yet always merely in the abstract, as concepts. Concepts are always the primary material of thought, and the forms of logic are always related to these, never directly to perception. Perception always determines only the material, never the formal truth of the proposition, for the formal truth is determined according to the logical rules alone.
I return to the Kantian philosophy, and come now to the Transcendental Dialectic. Kant opens it with the explanation of reason, the faculty which is to play the principal part in it, for hitherto only sensibility and understanding were on the scene. When considering his different explanations of reason, I have already spoken above of the explanation he gives here that “it is the faculty of principles.” It is now taught here that all the a priori knowledge hitherto considered, which makes pure mathematics and pure natural science possible, affords only rules, and no principles; because it proceeds from perceptions and forms of knowledge, and not from mere conceptions, which is demanded if it is to be called a principle. Such a principle must accordingly be knowledge from pure conceptions and yet synthetical. But this is absolutely impossible. From pure conceptions nothing but analytical propositions can ever proceed. If conceptions are to be synthetically and yet a priori combined, this combination must necessarily be accomplished by some third thing, through a pure perception of the formal possibility of experience, just as synthetic judgments a posteriori are brought about through empirical perception; consequently a synthetic proposition a priori can never proceed from pure conceptions. In general, however, we are a priori conscious of nothing more than the principle of sufficient reason in its different forms, and therefore no other synthetic judgments a priori are possible than those which proceed from that which receives its content from that principle.
However, Kant finally comes forward with a pretended principle of the reason answering to his demand, yet only with this one, from which others afterwards follow as corollaries. It is the principle which Chr. Wolf set up and explained in his “Cosmologia,” sect. i. c. 2, § 93, and in his “Ontologia,” § 178. As now above, under the title of the Amphiboly, mere Leibnitzian philosophemes were taken for natural and necessary aberrations of the reason, and were criticised as such, so here precisely the same thing happens with the philosophemes of Wolf. Kant still presents this principle of the reason in an obscure light, through indistinctness, indefiniteness, and breaking of it up (p. 307; V. 361, and 322; V. 379). Clearly expressed, however, it is as follows: “If the conditioned is given, the totality of its conditions must also be given, and therefore also the unconditioned, through which alone that totality becomes complete.” We become most vividly aware of the apparent truth of this proposition if we imagine the conditions and the conditioned as the links of a suspended chain, the upper end of which, however, is not visible, so that it might extend ad infinitum; since, however, the chain does not fall, but hangs, there must be above one link which is the first, and in some way is fixed. Or, more briefly: the reason desires to have a point of attachment for the causal chain which reaches back to infinity; it would be convenient for it. But we will examine the proposition, not in figures, but in itself. Synthetic it certainly is; for, analytically, nothing more follows from the conception of the conditioned than that of the condition. It has not, however, a priori truth, nor even a posteriori, but it surreptitiously obtains its appearance of truth in a very subtle way, which I must now point out. Immediately, and a priori, we have the knowledge which the principle of sufficient reason in its four forms expresses. From this immediate knowledge all abstract expressions of the principle of sufficient reason are derived, and they are thus indirect; still more, however, is this the case with inferences or corollaries from them. I have already explained above how abstract knowledge often unites a variety of intuitive cognitions in one form or one concept in such a way that they can no longer be distinguished; therefore abstract knowledge stands to intuitive knowledge as the shadow to the real objects, the great multiplicity of which it presents through one outline comprehending them all. Now the pretended principle of the reason makes use of this shadow. In order to deduce from the principle of sufficient reason the unconditioned, which directly contradicts it, it prudently abandons the immediate concrete knowledge of the content of the principle of sufficient reason in its particular forms, and only makes use of abstract concepts which are derived from it, and have value and significance only through it, in order to smuggle its unconditioned somehow or other into the wide sphere of those concepts. Its procedure becomes most distinct when clothed in dialectical form; for example, thus: “If the conditioned exists, its condition must also be given, and indeed all given, thus completely, thus the totality of its conditions; consequently, if they constitute a series, the whole series, consequently also its first beginning, thus the unconditioned.” Here it is false that the conditions of a conditioned can constitute a series. Rather must the totality of the conditions of everything conditioned be contained in its nearest ground or reason from which it directly proceeds, and which is only thus a sufficient ground or reason. For example, the different determinations of the state which is the cause, all of which must be present together before the effect can take place. But the series, for example, the chain of causes, arises merely from the fact that we regard what immediately before was the condition as now a conditioned; but then at once the whole operation begins again from the beginning, and the principle of sufficient reason appears anew with its claim. But there can never be for a conditioned a properly successive series of conditions, which exist merely as such, and on account of that which is at last conditioned; it is always an alternating series of conditioneds and conditions; as each link is laid