Nonsense. It's mostly the vastly larger number of available high entropy states vs low entropy states that transitions from high to low are never observed in macroscopic systems. True on a classical or quantum mechanical basis. Energy constraints are another factor - dispelling some popular and erroneous claims e.g. all the air in a room could spontaneously rush into one small corner. No. Statistical mechanics had been derived classically but not on a fully self-consistent basis: https://www.phas.ubc.ca/~birger/boltzmann/node2.html Planck actually gave the vital initial clue way before Feynman path integrals came along. Quantization of energy - which solved the 'ultraviolet catastrophe' problem plaguing classical attempts to explain blackbody radiation. From then on previous ad hoc coarse-graining assumptions used by Maxwell, Boltzmann et. al. could be dispensed with. 'Feynman' as word appears nowhere in this article: https://arxiv.org/abs/quant-ph/0511225 Please supply a link to a reputable article where Feynman path integrals are actually a basis for developing statistical mechanics quantum mechanically. I'm skeptical.