HUMAN AND MACHINE LOGIC: A REJOINDER

absence of axiomatic restrictions shows that future extensions of particle theory (as outlined above) might admit both re-entrant and non-re-entrant processes, and that such an admission might best be viewed as the discovery of a new class of physical processes rather than as a change in the meaning of fundamental concepts. We see then that the conceptual possibility of re-entrance is a question to be decided not by conceptual analysis but by physics.