  After briefly describing the present status of the spin glass theory, we
present a conjecture on the exact location of the multicritical point in the
phase diagram of finite-dimensional spin glasses. The theory enables us to
understand in a unified way many numerical results for two-, three- and
four-dimensional models including the +-J Ising model, random Potts model,
random lattice gauge theory, and random Zq model. It is also suggested from the
same theoretical framework that models with symmetric distribution of
randomness in exchange interaction have no finite-temperature transition on the
square lattice.
