On the Fourfold Root of the Principle of Sufficient...

All knowledge presupposes Subject and Object. Even self-consciousness (Selbstbewusstsein) therefore is not absolutely simple, but, like our consciousness of all other things (i.e., the faculty of perception), it is subdivided into that which is known and that which knows. Now, that which is known manifests itself absolutely and exclusively as Will.

The Subject accordingly knows itself exclusively as willing, but not as knowing. For the ego which represents, never can itself become representation or Object, since it conditions all representations as their necessary correlate; rather may the following beautiful passage from the Sacred Upanishad be applied to it: Id videndum non est: omnia videt; et id audiendum non est: omnia audit; sciendum non est: omnia scit: et intelligendum, non est: omnia intelligit. Præter id, videns, et sciens, et audiens, et intelligens ens aliud non est.[151]

My answer to the objection, "I not only know, but know also that I know," would be, "Your knowing that you know only differs in words from your knowing. 'I know that I know' means nothing more than 'I know,' and this again, unless it is further determined, means nothing more than 'ego.' If your knowing and your knowing that you know are two different things, just try to separate them, and first to know without knowing that you know, then to know that you know without this knowledge being at the same time knowing." No doubt, by leaving all special knowing out of the question, we may at last arrive at the proposition "I know"—the last abstraction we are able to make; but this proposition is identical with "Objects exist for me," and this again is identical with "I am Subject," in which nothing more is contained than in the bare word "I."

Now, it may still be asked how the various cognitive faculties belonging to the Subject, such as Sensibility, Understanding, Reason, are known to us, if we do not know the Subject. It is not through our knowing having become an Object for us that these faculties are known to us, for then there would not be so many conflicting judgments concerning them; they are inferred rather, or more correctly, they are general expressions for the established classes of representations which, at all times, have been more or less clearly distinguished in those cognitive faculties. But, with reference to the necessary correlate of these representations as their condition, i.e., the Subject, these faculties are abstracted from them (the representations), and stand consequently towards the classes of representations in precisely the same relation as the Subject in general towards the Object in general. Now, just as the Object is at once posited with the Subject (for the word itself would otherwise have no meaning), and conversely, as the Subject is at once posited with the Object—so that being the Subject means exactly as much as having an Object, and being an Object means the same thing as being known by the Subject—so likewise, when an Object is assumed as being determined in any particular way, do we also assume that the Subject knows precisely in that particular way. So far therefore it is immaterial whether we say that Objects have such and such peculiar inherent determinations, or that the Subject knows in such and such ways.

It is indifferent whether we say that Objects are divided into such and such classes, or that such and such different cognitive faculties are peculiar to the Subject. In that singular compound of depth and superficiality, Aristotle, are to be found traces even of insight into this truth, and indeed the critical philosophy lies in embryo in his works. He says:[152] ἡ ψυχὴ τὰ ὄντα πώς ἐστι πάντα (anima quammodo est universa, quæ sunt). And again: ὁ νοῦς ἐστι εἶδος εἰδῶν, i.e., the understanding is the form of forms, καὶ ἡ αἴσθησις εἶδος αἰσθητῶν, and sensibility the form of sensuous objects. Accordingly, it is all one whether we say, "sensibility and understanding are no more;" or, "the world is at an end." It comes to the same thing whether we say, "There are no conceptions," or "Reason is gone and animals alone remain."

The dispute between Realism and Idealism, which appeared for the last time in the dispute between the Dogmatists and Kantians, or between Ontology and Metaphysics on the one hand and Transcendental Æsthetic and Transcendental Logic on the other, arose out of the misapprehension of this relation and was based upon its misapprehension with reference to the First and Third Classes of representations as established by me, just as the mediæval dispute between Realists and Nominalists rested upon the misapprehension of this relation with reference to the Second Class.