 Schulman’s proposal in response to this asymmetry is that, just as the set of possible final microscopic states must be restricted for successful retrodiction, so should the permissible initial microscopic states be restricted for the purposes of prediction. Thus, since final microscopic states are subject to conditioning from the past state of the system, the initial microscopic states will be subject to conditioning from the future state of the system—a conditioning that is hidden in thermodynamic processes where the microscopic states of the system are indistinguishable macroscopically. This future conditioning is a central feature of Schulman’s two-time boundary condition proposal and the hidden nature of this conditioning Schulman calls “cryptic constraints”.