 Schulman (1997, 2012) proposes a solution to the quantum measurement problem based on the possibility of future conditioning, which originates from his analysis of the thermodynamic arrow of time. Beginning with Loschmidt’s challenge to Boltzmann—that it should not be possible to derive irreversible dynamical behavior from time-symmetric dynamics (see the entry on  thermodynamic asymmetry in time)—Schulman  notes that successful “retrodiction” of past macroscopic states of some thermodynamic system is indeed asymmetric to successful “prediction” of future macroscopic states. For successful retrodiction, rather than evolving each of the microscopic states of some macroscopic state according to the dynamical laws (which is identical to the process of prediction, and is the basis of Loschmidt’s challenge), one instead hypothesizes a prior macroscopic state to which the prediction process can be applied such that the current macroscopic state of the system obtains with high likelihood given the dynamical evolution of the prior microscopic states. With respect to the set of possible microscopic states for the current macroscopic state, since the evolution of the vast majority (on Liouville measure) of these states according to the dynamical laws result in trajectories that conflict with the retrodiction hypothesis, these states are effectively rejected in the process of retrodiction in favor of those special few microscopic states that correspond to the dynamical evolution of acceptable hypothetical initial conditions.