Relatedly, Galen at times makes a distinction between bodily features which were intended as part of the primary design or rationale (kata prōton logon) and those which follow by necessity, through physical causation, as a by-product of that design (Temp. II.5, 253; cf. UP XI.14, 534–36 on how providential design takes account of necessary physical consequences). Again, the consequence of such an analysis would seem to be that not all features of an animal can be equally part of a teleological account, or not part of it in the same sense. Certain things seem to happen spontaneously, or to follow unavoidably from the purposive cause, though not themselves intended.