Substitution is the opposite of transformation: the replacement of one thing by another; not continuity, not sameness in difference. "There are other kinds of change--one damn thing after another, for instance," Barfield writes in Unancestral Voice. "I would call that kind mere substitution, whereas evolution implies a process of transformation. The difference between transformation and substitution is that transformation involves the persistent presence of something common to both the old form and the new" (UV 96).

Darwinism treats evolutionary change as mere substitution.

See in particular Unancestral Voice, passim, What Coleridge Thought, passim.