Most philosophers are now convinced, however, that Quine's “mathematical cyclist” argument has been adequately answered by Saul Kripke (1972), Alvin Plantinga (1974) and various other defenders of modality de re. Kripke and Plantinga's defenses of modality are paradigmatically metaphysical (except insofar as they directly address Quine's linguistic argument). Both make extensive use of the concept of a possible world in defending the intelligibility of modality (both de re and de dicto). Leibniz was the first philosopher to use ‘possible world’ as a philosophical term of art, but Kripke's and Plantinga's use of the phrase is different from his. For Leibniz, a possible world was a possible creation: God's act of creation consists in his choosing one possible world among many to be the one world that he creates—the “actual” world. For Kripke and Plantinga, however, a possible world is a possible “whole of reality”. For Leibniz, God and his actions “stand outside” all possible worlds. For Kripke and Plantinga, no being, not even God, could stand outside the whole system of possible worlds. A Kripke-Plantinga (KP) world is an abstract object of some sort. Let us suppose that a KP world is a possible state of affairs (this is Plantinga's idea; Kripke says nothing so definite). Consider any given state of affairs; let us say, Paris being the capital of France.  This state of affairs obtains, since Paris is the capital of France. By contrast, the state of affairs Tours being the capital of France does not obtain. The latter state of affairs does, however, exist, for there is such a state of affairs. (Obtaining thus stands to states of affairs as truth stands to propositions: although the proposition that Tours is the capital of France is not true, there nevertheless is such a proposition.) The state of affairs x is said to include the state of affairs y if it is impossible for x to obtain and y not to obtain. If it is impossible for both x and y to obtain, then each precludes the other. A possible world is simply a possible state of affairs that, for every state of affairs x, either includes or precludes x; the actual world is the one such state of affairs that obtains.