clearly put forward for use in cases which arise, then from such a principle we can draw no explanation, i.e. no clear and determinate derivation of the possibility of a natural product in accordance with those two heterogeneous principles. But now the principle common to the mechanical and teleological derivations is the supersensible, which we must place at the basis of nature, regarded as phenomenon. And of this, in a theoretical point of view, we cannot form the smallest positive determinate concept. It cannot, therefore, in any way be explained how, according to it as principle, nature (in its particular laws) constitutes for us one system, which can be cognised as possible either by the principle of physical development or by that of final causes. If it happens that objects of nature present themselves which cannot be thought by