  A fundamental problem with attempting to quantize general relativity is its
perturbative non-renormalizability. However, this fact does not rule out the
possibility that non-perturbative effects can be computed, at least in some
approximation. We outline a quantum field theory calculation, based on general
relativity as the classical theory, which implies a phase transition in quantum
gravity. The order parameters are composite fields derived from spacetime
metric functions. These are massless below a critical energy scale and become
massive above it. There is a corresponding breaking of classical symmetry.
