In a recent book review of Maudlin’s The Metaphysics within Physics, Mauricio Suarez (Stud Hist Phil Mod Phys 40 (2009): 273-276) proposes an alternative argument against the Humean position Maudlin calls “physical statism” based on objective chance. Physical statism asserts that the physical state of the world completely determines all the facts, or, conversely, that all facts supervene on the physical state of the world. Together with separability, according to which the physical state of the world supervenes on the Humean mosaic, it entails Humean supervenience, which contends that all facts supervene on the Humean mosaic.
Suarez argues that the strongest argument against physical statism–one not adduced by Maudlin–trades on the existence of objective chance. Science, he says, shows that there are stochastic processes, i.e. “a temporal succession of states related by a particular transition probability” (275). Suarez takes the presence of transition probabilities to be a sufficient condition for there to be objective chance. But objective chance is incompatible with physical statism. Since objective chance is shown to exist by science, he concludes, physical statism is contingently false. In other words, physical statism must be rejected because it cannot capture the modal and nomological facts about this world.
True, objective chance has traditionally been seen as a problem for the Humean. But couldn’t the Humean consistently deny the reality of objective chance? True, the laws of quantum mechanics may involve an ineliminable element of stochasticity. But couldn’t the Humean consistently deny that there are modal facts about this (and only) world? The one interpretation of quantum mechanics which seems to invoke genuinely stochastic processes is GRW, at least if we only consider the three main interpretations on the market. But if we adorn GRW with a primitive ontology of local beables, say with a flash ontology, then what we have is a distribution of flashes in spacetime. Of course we can think of this distribution as expressible in terms of objectively interpreted probabilities. But the actual world just consists of a given flash distribution, and that’s it. The substructure of the actual world that is being describes harbors no modal facts or anything of the sort. Modality only enters once we offer a theory describing that substructure.
So it seems to me that the Humean could just deny that there are modal facts and I don’t see what in quantum mechanics would force her otherwise…