  We consider the problem of identifying the CFT's that may be dual to pure
gravity in three dimensions with negative cosmological constant. The c-theorem
indicates that three-dimensional pure gravity is consistent only at certain
values of the coupling constant, and the relation to Chern-Simons gauge theory
hints that these may be the values at which the dual CFT can be holomorphically
factorized. If so, and one takes at face value the minimum mass of a BTZ black
hole, then the energy spectrum of three-dimensional gravity with negative
cosmological constant can be determined exactly. At the most negative possible
value of the cosmological constant, the dual CFT is very likely the monster
theory of Frenkel, Lepowsky, and Meurman. The monster theory may be the first
in a discrete series of CFT's that are dual to three-dimensional gravity. The
partition function of the second theory in the sequence can be determined on a
hyperelliptic Riemann surface of any genus. We also make a similar analysis of
supergravity.
