Wheeler on “basic quantities of nature”

After many months of letting it sit around, I took a glance at the Chandrasekhar-autographed (-owned?) relativity conference volume I’d bought for almost nothing at a library book sale. Wheeler has a paper in there on “superspace”, which for him meant the configuration space of general relativity. He speaks of a theory in which the universe undergoes cycles of collapse and re-expansion, with properties like its number of dimensions, its coupling constants, and its particle masses coming out different with each re-expansion. Then he explains why, in this theory, a particle mass is not a “basic quantity of nature”:

On this view a particle mass is not a basic quantity of nature. It has as little claim to that title as does the mass of the water droplet that hangs from the ceiling of the shower. Ask why it has its mass, and find oneself asking why one takes a shower where the value of g happens to be 980cm/sec². Ask why the particle has its mass, and end up asking why we happen to be living in this particular cycle of the universe. One cycle, one set of masses. Another cycle, another set of masses. That is the picture.

The paragraph itself raises interesting questions, of course. It seems that Wheeler’s idea of a ‘basic quantity of nature’ is a quantity that isn’t explained (or caused?) by what I roughly think of as ‘contingent’ physical configurations of the universe. But the notions of ‘contingency’ and explanation (or cause) aren’t fleshed out.

What interested me more, though, was that Wheeler has a reference in this paragraph to Leibniz’s Théodicée, Leibniz’s correspondence with Samuel Clarke, Landau and Lifshitz’s Statistical Physics, and a few physics papers from the 1960s. It’s been nearly two years since I read the Leibniz-Clarke correspondence, but I can’t recall anything in there that is obviously relevant to Wheeler’s point about basic quantities of nature. The Principle of Sufficient Reason? If we take PSR seriously, though, we’d have to say there aren’t any ‘unexplained’ (again, lacking a firm notion of explanation here) physical quantities, which is a quite different thing from saying that if a physical quantity is explained by some contingent physical configuration, then it is not a basic quantity of nature. That is, PSR would seem to rule out unexplained physical quantities rather than serving as a justification for classifying them as ‘basic’ quantities.

And — what do Landau and Lifshitz say that is remotely related to what Leibniz said, or to Wheeler’s point?