Kant has nowhere made the thing in itself the subject of a special exposition or distinct deduction; but, whenever he wants it, he introduces it at once by means of the conclusion that the phenomenon, thus the visible world, must have a reason, an intelligible cause, which is not a phenomenon, and therefore belongs to no possible experience. He does this after having assiduously insisted that the categories, and thus causality also, had a use which was absolutely confined to possible experience; that they were merely forms of the understanding, which served to spell out the phenomena of the world of sense, beyond which, on the other hand, they had no significance, &c., &c. Therefore, he denies in the most uncompromising manner their application to things beyond experience, and rightly explains and at once rejects all earlier dogmatism as based upon the neglect of this law. The incredible inconsistency which Kant here fell into was soon noticed, and used by his first opponents to make attacks on his philosophy to which it could offer no resistance. For certainly we apply the law of causality entirely _a priori_ and before all experience to the changes felt in our organs of sense. But, on this very account, this law is just as much of subjective origin as these sensations themselves, and thus does not lead to a thing in itself. The truth is, that upon the path of the idea one can never get beyond the idea; it is a rounded-off whole, and has in its own resources no clue leading to the nature of the thing in itself, which is _toto genere_ different from it. If we were merely perceiving beings, the way to the thing in itself would be absolutely cut off from us. Only the other side of our own being can disclose to us the other side of the inner being of things. This path I have followed. But Kant’s inference to the thing in itself, contrary as it is to his own teaching, obtains some excuse from the following circumstance. He does not say, as truth required, simply and absolutely that the object is conditioned by the subject, and conversely; but only that the manner of the appearance of the object is conditioned by the forms of knowledge of the subject, which, therefore, also come _a priori_ to consciousness. But that now which in opposition to this is only known _a posteriori_ is for him the immediate effect of the thing in itself, which becomes phenomenon only in its passage through these forms which are given _a priori_. From this point of view it is to some extent explicable how it could escape him that objectivity in general belongs to the form of the phenomenon, and is just as much conditioned by subjectivity in general as the mode of appearing of the object is conditioned by the forms of knowledge of the subject; that thus if a thing in itself must be assumed, it absolutely cannot be an object, which however he always assumes it to be, but such a thing in itself must necessarily lie in a sphere _toto genere_ different from the