  It is no longer considered surprising that black holes have temperatures and
entropies. What remains surprising, though, is the universality of these
thermodynamic properties: their exceptionally simple and general form, and the
fact that they can be derived from many very different descriptions of the
underlying microscopic degrees of freedom. I review the proposal that this
universality arises from an approximate conformal symmetry, which permits an
effective "conformal dual" description that is largely independent of the
microscopic details.
