  Before Vic Emery's untimely death, we had the privilege of working closely
with him on the role of Coulomb frustrated phase separation in doped Mott
insulators, and on the consequences of the resulting local electronic
structures on the "mechanism" of high temperature superconductivity. In the
present article, we discuss the resulting perspective on superconductivity in
the cuprates, and on the more general theoretical issue of what sorts of
systems can support high temperature superconductivity. We discuss some of the
general, qualitative aspects of the experimental lore which we think should
constrain any theory of the mechanism, and show how they are accounted for
within the context of our theory.
