Page History

...

I more and more see the need to consider carefully just how the following three things are both similar to and different from one another:

Wiki Markup1. Hartshorne's threefold division of "knowledge" into "\[1\] mathematics, dealing with various '_possible_ worlds,' or better, various _possible_ logical structures; \ [2\] natural and social science, dealing with the one _actual_ world; \ [3\] metaphysics, dealing with what is common and _necessary_ to all possible states of affairs and all possible truth, including adjudication of the question of whether 'there is no world at all' represents a conceivable truth or is mere nonsense or contradiction" (_The Divine Relativity_: xiii).

2. Goodwin's threefold distinction of "truths" into (1) "contingent truths" that are "true in some possible worlds and false in other possible worlds"; (2) "conditionally necessary truths" that are "necessarily true in some possible worlds and false in no possible worlds" and therefore are also "nonexistential necessary truths"; and (3) "unconditionally necessary truths" whose criterion is not only "falsity in no possible world," but "truth in all possible worlds"  and which therefore are "existential" as well as "necessary" (The Ontological Argument of Charles Hartshorne: 14, 17 f., 19 f.).

...