Theoretical Frameworks for Testing Relativistic Gravity. I. Foundations

This is the first in a series of theoretical papers which will discuss the experimental foundations of general relativity. This paper reviews, modifies, and compares two very different theoretical frameworks, within which one devises and analyzes tests of gravity. The Dicke framework assumes almost nothing about the nature of gravity; and it uses a variety of experiments to delineate the gross features of the gravitational interaction. Two of its tentative conclusions (the presence of a metric, and the "gravitational response equation," V T = 0, for stressed matter) become the postulates of the Parametrized PostNewtonian framework. The PPN framework encompasses most, if not all, of the theories of gravity that are currently compatible with experiment. Future papers in this series will develop the PPN framework in detail, and will use it to analyze a variety of relativistic gravitational effects that should be detectable in the solar system during the coming decade