Nature Has No “Logical Structure”
A defense of moderate logical exceptionalism
Hilary Putnam claimed that the following analogy was “perfect”: just as general relativity forced us to revise supposedly necessary truths about the geometry of our world, so quantum mechanics forces us to revise supposedly necessary truths about the logic of our world.
His claim was justly rejected by the literature, but the underlying Quinean premise that logic could be reconsidered in light of physical evidence, or that it could differ between possible worlds, has not been seen through.
The third chapter of my dissertation (see below) begins the project of undermining this claim, starting from the case of quantum mechanics and extrapolating from there. This will ultimately put pressure on views about logic shared by Quine and Carnap.
“Looking for Logic in All the Wrong Places: Extrapolating from the Quantum Case” builds on recent work by Saul Kripke and Tim Maudlin in explaining not only why a “quantum logic” like Putnam’s had to fail, but why the more general notion of a “physical logic” analogous to “physical geometry” is ill-conceived. I argue that the sense in which we could discover a “logic” in nature is fully distinct from “logic” as a set of inference rules that are truth-preserving regardless of subject matter. Thus it is a mistake to attempt to consider whether the world “operates” by this or that logic. The argument is independent from, but coheres with, Kripke’s arguments about the difficulty of making coherent sense of the notion of adopting a logic. In conclusion I speculate about what tempts us to sometimes see a revision of logic as a plausible possibility.