Hence (medical) physiology extends its very limited empirical acquaintance with the ends served by the structure of an organic body through a principle prompted merely by pure reason and this to such an extent that it is assumed confidently, and with the agreement of all who understand the matter, that everything in an animal has its utility and good aim; this presupposition, if it is supposed to be constitutive, goes much further than previous observation can justify; from this it can be seen that it is nothing but a regulative principle a of reason for attaining to the highest systematic unity by means of the idea of the purposive causality of the supreme cause of the world, as if this being, as the highest intelligence, were the cause of everything according to the wisest aim.