Does classical mechanics always adequately describe "classical physical reality"
The article is dedicated to discussion of irreversibility and foundation of statistical mechanics "from the first principles". Taking into account infinitesimal and, as it seems, neglectful for classical mechanics fluctuations of the physical vacuum, makes a deterministic motion of unstable dynamic systems is broken ("spontaneous determinism breaking", "spontaneous stochastization"). Vacuum fluctuations play part of the trigger, starting the powerful mechanism of exponent instability. The motion of the dynamic systems becomes irreversible and stochastic. Classical mechanics turns out to be applicable only for a small class of stable dynamic systems with zero Kolmogorov-Sinay entropy $h=0$. For alternative "Stochastic mechanics" there are corresponding equations of motion and Master Equation, describing irreversible evolution of the initial distribution function to equilibrium state.