 Of course, there is much discussion of the “approximately classical” or “quasi-classical” trajectories for quantum systems that can be derived from semi-classical considerations (Berry 1987 and 2001). But such quasi-classical behavior is exhibited only for limited times (except for overly idealized models) and under very special initial conditions (Pauli 1933, p. 166) for ground states only (excited energy eigenstates never show classical behavior). Appeal to Ehrenfest’s theorem is of no help, here, because all this theorem guarantees for such very special, short-lived dynamics is that the usual physics practice of averaging the values of the quantum-mechanical observables tends to wash out the errors or differences between the classical and quantum calculations for contextually relevant situations and times. Moreover, the theorem is neither necessary nor sufficient for classical behavior. For instance, applying Ehrenfest’s theorem to a quantum harmonic oscillator yields average quantities for the position and momentum that track with the classical quantities for some brief time. Yet, the quantum oscillator’s discrete states yield thermodynamic properties very different from a classical oscillator. So satisfying the theorem is insufficient to guarantee classical behavior. 