Of the principle of judging of internal purposiveness in organised beings

This principle, which is at the same time a definition, is as follows: An organised product of nature is one in which every part is reciprocally purpose, [end] and means. In it nothing is vain, without purpose, or to be ascribed to a blind mechanism of nature.

This principle, as regards its occasion, is doubtless derived from experience, viz. from that methodised experience called observation; but on account of the universality and necessity which it ascribes to such purposiveness it cannot rest solely on empirical grounds, but must have at its basis an a priori principle, although it be merely regulative and these purposes lie only in the idea of the judging [subject] and not in an effective cause.