  Why do gases reach equilibrium when left to themselves? The canonical answer,
originally proffered by Boltzmann, is that the systems have to be ergodic. This
answer is now widely regarded as flawed. We argue that some of the main
objections, in particular, arguments based on the KAM-theorem and the
Markus-Meyer theorem, are beside the point. We then argue that something close
to Boltzmann's proposal is true: gases behave thermodynamic-like if they are
epsilon-ergodic, i.e., ergodic on the phase space except for a small region of
measure epsilon. This answer is promising because there is evidence that
relevant systems are epsilon-ergodic.
