determination by the law of causality extend. Let us leave, however, concrete nature and pass over to abstract thinking; then we can present to ourselves in reflection all the natural laws which are known to us partly a priori, partly only a posteriori, and this abstract idea contains all that is in nature at any time, in any place, but with abstraction from every definite time and place; and just in this way, through such reflection, we have entered the wide kingdom of the possible. But what finds no place even here is the impossible. It is clear that possibility and impossibility exist only for reflection, for abstract knowledge of the reason, not for knowledge of perception; although it is the pure forms of perception which supply the reason with the determination of the possible and impossible. According as the laws of nature, from which we start in the thought of the possible and impossible, are known a priori or a posteriori, is the possibility or impossibility metaphysical or physical.
From this exposition, which requires no proof because it rests directly upon the knowledge of the principle of sufficient reason and upon the development of the conceptions of the necessary, the actual, and the possible, it is sufficiently evident how entirely groundless is Kant's assumption of three special functions of the understanding for these three conceptions, and that here again he has allowed himself to be disturbed by no reflection in the carrying out of his architectonic symmetry.
To this, however, we have to add the other great mistake, that, certainly according to the procedure of earlier philosophy, he has confounded the conceptions of necessity and contingency with each other. That earlier philosophy has applied abstraction to the following mistaken use. It was clear that that of which the reason is given inevitably follows, i.e., cannot not be, and thus necessarily is. But that philosophy held to this last determination alone, and said that is necessary which cannot be otherwise, or the opposite of which is impossible. It left, however, the
