ROLE OF TIME IN THE SUM-OVER-HISTORIES FRAMEWORK FOR GRAVITY

I sketch a self-contained framework for quantum mechanics based on its path-integral or ''sum-over-histories'' formulation. The framework is very close to that for classical stochastic processes like Brownian m otion, and its interpretation requires neither ''measurement'' nor ''s tate-vector'' as a basic notion. The rules for forming probabilities a re nonclassical in two ways: they use complex amplitudes, and they (ap parently unavoidably) require one to truncate the histories at a ''col lapse time,'' which can be chosen arbitrarily far into the furniture. Adapting this framework to gravity yields a formulation of quantum gra vity with a fully ''spacetime'' character, thereby overcoming the ''fr ozen nature'' of the canonical formalism. Within the proposed adaptati on, the value of the ''collapse time'' is identified with total ''elap sed'' spacetime four-volume. Interestingly, this turns the cosmologica l constant into an essentially classical constant of integration, remo ving the need for microscopic ''fine tuning'' to obtain an experimenta lly viable value for it. Some implications of the ''V = T'' rule for q uantum cosmology are also discussed.