Nineteenth-century Darwinism was much more than a revolutionary scientific theory.
It’s helpful, as with his Third Way, to begin with a metaphor, in order to get an intuitive feel for the proof.
Imagine that you are an astronomer on a world with one moon. It is always night on your world, and the moon is the only body in the sky.
Nature is like a stack of books, sessile, until moved.
In my ongoing debate with biologist Jerry Coyne, frequent reference is made to Aquinas’ Five Ways, particularly to his Prime Mover argument.