 Process theism is not based on religious doctrine or theology and it is not a scientific theory; it is a product of metaphysics, or what Whitehead calls “speculative philosophy.” It is, however, metaphysics “in a new key,” to borrow a phrase from Susanne Langer. Whitehead says that, “Speculative philosophy is the endeavour to frame a coherent, logical, necessary system of general ideas in terms of which every element of our experience can be interpreted” (Whitehead 1929 [1978, 3]). Metaphysics, so defined, is an audacious enterprise, for experience is open-ended and every claim to knowledge is perspectival and conditioned. If metaphysicians strive for a comprehensive vision of things, they must continually remind themselves that there is no standpoint within the world from which to speak confidently for eternity. Whitehead and Hartshorne reject the idea that metaphysics proceeds best by deducing theorems from self-evident axioms. To be sure, inferences must be made from the categories of one’s metaphysics, but it is the categories themselves that are continually on trial. The court in which metaphysical proposals are judged is the community of philosophers, stretching through history and into the future. Whitehead and Hartshorne, heavily influenced by Plato, practice philosophy as a dialogue with great minds, past and present. Hartshorne, taking a page from Karl Popper, says that, “Objectivity is not in the individual thinker but in the process of mutual correction and inspiration” (Hartshorne 1962, ix).