No, it is not "just the motions of particles"! This is material monism, aka physicalism. It has a well known open problem: it has no causal theory of the subjective experiences that we have, no explanation for how it is even possible to have a "what it is like to be Brian Green". This alone should make him pause! <br>What could the solution be? What if some form of dualism is actually possible, a dualism that does not have the poison pill of the belief in "primitive substances"!