  In the Feynman formalism of quantum mechanics one encounters a postulate,
namely, that the propagator in an infinitesimal time-interval is the classical
wave function. This postulate, which was later studied thoroughly by Holland,
was recently highlighted by using the improved Makri-Miller propagator. The
present note, whose conclusion is in agreement with that recent achievement,
demonstrates that the Heisenberg picture of quantum mechanics invariably
includes the Feynman postulate and is able to yield a proof for it. In other
words, by starting out from the Heisenberg picture, it is proved that when
terms of second-order in time can be neglected, the dynamics of a system is
classical.
