I think the point there is that on a deterministic view, in which everything is necessitated, nothing's more "fundamental" than anything else. Everything would be just a link in the causal chain. But the necessity in that kind of natural causality is dubious, as Hume pointed out. That causal necessity is an "occult" quality in which some kind of divine mind would hide. So this determinism wouldn't undermine the dichotomy I'm positing; rather, it would entail (in an obfuscating way) that life is metaphysically fundamental.