Tuning, ergodicity, equilibrium, and cosmology

I explore the possibility that the cosmos is fundamentally an equilibrium system and review the attractive features of such theories. Equilibrium cosmologies are commonly thought to fail due to the ``Boltzmann brain'' problem. I show that it is possible to evade the Boltzmann brain problem if there is a suitable coarse-grained relationship between the fundamental degrees of freedom and the cosmological observables. I make my main points with simple toy models and then review the de Sitter equilibrium model as an illustration.