Things regarded as natural purposes are organised beings

According to the character alleged in the preceding section, a thing, which, though a natural product, is to be cognised as only possible as a natural purpose, must bear itself alternately as cause and as effect. This, however, is a somewhat inexact and indeterminate expression which needs derivation from a determinate concept.

Causal combination as thought merely by the Understanding is a connexion constituting an ever-progressive series (of causes and effects); and things which as effects presuppose others as causes cannot be reciprocally at the same time causes of these. This sort of causal combination we call that of effective causes (nexus effectivus). But on the other hand, a causal combination according to a concept of Reason