"Nothing changes itself. Apparently self-moving things, like animal bodies, are moved by desire or will—something other than mere molecules. "
This is, of course, untrue. If you want an example of molecules changing, concider the hydrogen inside the Sun being converted to helium. There are enormous-but-well-understood forces at work - mainly high temperature and pressure - which cause these molecules to change from one form to another. No desire, no will. That's just how molecules behave under those conditions. The same argument used to be made about lightning. What caused lightning? Must be the gods' wills! Once we understood static charges, the need for god simply vanished.
Oh CZ. You so misunderstand the way things work. The Hydrogen would not turn to helium without the Flying Spaghetti Monster touching each and every one with his (or is it her?) noodley appendage. Its like balls on a billiards table. Duh! It takes someone with the magical pool stick and a cue ball to get the balls going!