Griffin, David Ray.  "Process Theology as Empirical, Rational, and Speculative: Some Reflections on Method."  Process Studies 19, no. 2 (Summer 1990): 116-135.

Abstract

Written for a conference bringing together advocates of the so-called empirical, rationalistic, and speculative forms of process theology, this essay defends the "s" word.  Christian theology today, now that the method of authority is impossible, must seek to be both fully empirical and fully rational, making its claim to truth in terms of the normal criteria of self-consistency and adequacy to the facts (the latter criterion is defended against current detractors).  Seeking to realize this idea of rational empiricism requires speculation, meaning the formation of hypotheses about what things are in themselves.  [Abstract from The Philosopher's Index]