Time-Symmetrized Quantum Theory, Counterfactuals, and `Advanced Action'

Abstract

Recent authors have raised objections to the counterfactual interpretation of the Aharonov-Bergmann-Lebowitz (ABL) rule of time symmetrized quantum theory (TSQT). I distinguish between two different readings of the ABL rule, counterfactual and non-counterfactual, and confirm that TSQT advocate L. Vaidman is employing the counterfactual reading to which these authors object. Vaidman has responded to the objections by proposing a new kind of time-symmetrized counterfactual, which he has defined in two different ways. It is argued that neither definition succeeds in overcoming the objections, except in a special case previously noted by Cohen and Hiley. In addition, a connection is made between TSQT and Price's concept of `advanced action', which further supports the special case discussed.