“Is logic empirical?”

Main article: Is logic empirical?

What is the epistemological status of the laws of logic? What sort of argument is appropriate for criticizing purported principles of logic? In an influential paper entitled “Is logic empirical?”^[37]Hilary Putnam, building on a suggestion of W. V. Quine, argued that in general the facts of propositional logic have a similar epistemological status as facts about the physical universe, for example as the laws of mechanics or of general relativity, and in particular that what physicists have learned about quantum mechanics provides a compelling case for abandoning certain familiar principles of classical logic: if we want to be realists about the physical phenomena described by quantum theory, then we should abandon the principle of distributivity, substituting for classical logic the quantum logic proposed by Garrett Birkhoff and John von Neumann.^[38]

Another paper of the same name by Sir Michael Dummett argues that Putnam’s desire for realism mandates the law of distributivity.^[39] Distributivity of logic is essential for the realist’s understanding of how propositions are true of the world in just the same way as he has argued the principle of bivalence is. In this way, the question, “Is logic empirical?” can be seen to lead naturally into the fundamental controversy in metaphysics on realism versus anti-realism.