Some Consequences of Physics for the Comparative Metaphysics of Quantity

According to comparativist theories of quantities, their intrinsic values are not fundamental. Instead, all the quantity facts are grounded in scale-independent relations like “twice as massive as” or “more massive than.” I show that this sort of scale independence is best understood as a sort of metaphysical symmetry—a principle about which transformations of the non-fundamental ontology leave the fundamental ontology unchanged. Determinism—a core scientific concept easily formulated in absolutist terms—is more difficult for the comparativist to define. After settling on the most plausible comparativist understanding of determinism, I offer some examples of physical systems that the comparativist must count as indeterministic, although the relevant physical theory gives deterministic predictions. Several morals are drawn. In particular: comparativism is metaphysically contingent if true, and it is most natural for a comparativist to accept an at-at theory of motion.