  Even without going that far, though, the shift to a quantum dynamical basis just require some rethinking of subtle issues in the foundational debates.  From the earliest days Poincare's Recurrence Theorem was a problem for statistical mechanics.  With a classical dynamical basis a reply could be made that while the Theorem held for individual systems of the concern of the theory, it would not necessarily hold of an ensemble of such systems.  Once one moves to a quantum mechanical basis this “way out” is no longer available.  In both dynamical frameworks, however, a move to the thermodynamic limit of an infinite number of constituents for a system can eliminate the applicability of the theorem as an objection to the monotonicity of thermodynamic change being unobtainable in statistical mechanics.