  The standard model of particle physics is marvelously successful. However, it
is obviously not a complete or final theory. I shall argue here that the
structure of the standard model gives some quite concrete, compelling hints
regarding what lies beyond. Taking these hints seriously, one is led to predict
the existence of new types of very weakly interacting matter, stable on
cosmological time scales and produced with cosmologically interesting
densities--that is, ``dark matter''.
