Boltzmann’s approach to statistical mechanics is widely believed to be conceptually superior to Gibbs’ formulation. However, the microcanonical distribution often fails to behave as expected: The ergodicity of the motion relative to it can rarely be established for realistic systems; worse, it can often be proved to fail. Also, the approach involves idealizations that have little physical basis. Here we take Khinchin’s advice and propose a de…nition of equilibrium that is more realistic: The de…nition re‡ects the fact that the system (...) is made of a great number of particles, and implies that all measurable macroscopic observables have steady values. (shrink)