So when it is said that nature specifies its universal laws on a principle of purposiveness for our cognitive faculties, ie of suitability for the human understanding and its necessary function of finding the universal for the particular presented to it by perception, and again for varieties (which are, of course, common for each species) connexion in the unity of principle, we do not thereby either prescribe a law to nature, or learn one from it by observation although the principle in question may be confirmed by this means.