Logical system that differs from classical logic in ways that reflect the inferential relations between propositions in quantum theory. The models of such logics differ in various ways from classical Boolean algebras. Such a logic was first propounded by G. Birkhoff and John von Neumann, in 1936. A typical, but not universal, feature of quantum logics is failure of the distributive law that from A & (B ⁄ C) can be inferred (A & B) ⁄ (A & C). It was argued by Putnam that this failure reflects the strange behaviour of quantum particles in two-slit experiments (see quantum theory).