But what is most curious in this matter is this—the discovery that Kant did not intend to speak of a something different from the Ego, is by no means a new one. For ten years everybody could read the most thorough and complete proof of it in Jacobi’s “Idealism and Realism,” and in his “Transcendental Idealism.” In those works, Jacobi has put together the most evident and decisive passages from Kant’s writings on this subject, in Kant’s own words. I do not like to do again what has once been done, and cannot be done better; and I refer my readers with the more pleasure to those works, as they, like all philosophical writings of Jacobi, may be even yet of advantage to them. A few questions, however, I propose to address to those interpreters of Kant. Tell me, how far does the applicability of the categories extend, according to Kant, particularly of the category of causality? Clearly only to the field of appearances, and hence only to that which is already in us and for us. But in what manner do we then come to accept a something different from the Ego, as the ground of the empirical content of Knowledge? I answer: only by drawing a conclusion from the grounded to the ground; hence by applying the category of causality. Thus, indeed, Kant himself discovers it to be, and hence rejects the assumption of _things, &c., &c., outside of us_. But his interpreters make him forget for the present instance the validity of categories generally, and make him arrive, by a bold leap, from the world of appearances to the thing _per se_ outside of us. Now, how do these interpreters justify this inconsequence? Kant evidently speaks of a thing _per se_. But what is this thing to him? A _noumenon_, as we can find in many passages of his writings. Reinhold and Schulz also hold it to be a _noumenon_. Now, what is a _noumenon_? According to Kant, to Reinhold, and Schulz, a something, which our _thinking_—by laws to be shown up, and which Kant has shown up—_adds_ to the appearance, and which _must_ so be added in _thought_;[8] which, therefore, is produced _only through our thinking_; not, however, through our _free_, but through a _necessary_ thinking, which is only _for our thinking_—for us thinking beings.