meritorious, to pursue natural mechanism, in respect of the explanation of natural products, so far as can be done with probability; and if we give up the attempt it is not because it is impossible in itself to meet in this path with the purposiveness of nature, but only because it is impossible for us as men. For there would be required for that an intuition other than sensuous, and a determinate knowledge of the intelligible substrate of nature from which a ground could be assigned for the mechanism of phenomena according to particular laws, which quite surpasses our faculties.

Hence if the naturalist would not waste his labour he must in judging of things, the concept of any of which is indubitably established as a natural purpose (organised beings), always lay down as basis an original