I will argue, pace a great many of my contemporaries, that there's something right about Boltzmann's attempt to ground the second law of thermodynamics in a suitably amended deterministic time-reversal invariant classical Hamiltonian mechanics and that in order to appreciate what's right about (what was at least at one time) Boltzmann's explanatory project one has to fully apprehend the nature of (a) microphysical causal structure, (b) time-reversal invariance, and (c) the relationship between the Boltzmann entropy and the work of Rudolf Clausius.
Link to Professor Weaver's handout:
Works cited In Praise of Clausius Entropy