I'm not so sure -- he also says that what he calls "will" is in non-living universe equal to physical forces, whereas in living beings it equals to blind instincts (or biological impulses). That's by definition the antithesis of deliberation, no matter how anthropocentric that analogy might be.

Where he does bring up willpower is that the "will (of life)", while it cannot be subdued, can be deliberately rejected (in ascetic manner). Which, however, only further reinforces what I say.