Causal anomalies and the completeness of quantum theory

Abstract

Hans Reichenbach’s Philosophic Foundations of Quantum Mechanics (1944) has attracted the attention of philosophers because of its proposal for the interpretation of the theory in terms of a non-standard, threevalued logic.1 Such an interpretation is, as Reichenbach calls it, a ‘restrictive’ one; that is, it leaves certain propositions formulable in the language of the theory without standard truth conditions.2 These propositions can be neither verified nor falsified, and the facts they express thus neither predicted nor explained by the theory. A typical such proposition assigns a determinate position and momentum to a particle at some instant. Clearly, embracing such an interpretation involves renouncing a spacetime description of the world, and is thus not to be entered into lightly.