  I argue that isolated vacua of M-theory, cannot in any conventional way be
said to live in the same theory as other disconnected parts of the moduli
space. The usual field theoretic mechanisms, which allow an observer in one
disconnected component of a moduli space to verify the existence of other
components, fail. The failure is a consequence of robust properties of black
holes. When barriers between components are much smaller than the Planck scale,
the usual field theoretic picture is approximately valid.
