On an unsound proof of the existence of possible worlds.
Christopher Menzel · Notre Dame Journal of Formal Logic · 1989
In this paper, an argument of Alvin Plantinga's for the existence of abstract possible worlds is shown to be unsound.The argument is based on a principle Plantinga calls "Quasicompactness", due to its structural similarity to the notion of compactness in first-order logic.The principle is shown to be false.The concept of possible worlds has been of great value to the development of modal logic, metaphysics, and the philosophy of language over the past thirty years or so.However, there is still a great deal of controversy regarding the nature of these entities.Are they concrete?Abstract?Indeed, are there really any such things at all, or is the concept merely heuristically useful?Much of this controversy stems from the fact that, typically, accounts of possible worlds simply postulate their existence, usually offering by way of justification no more (and no less) than the theoretical elegance and usefulness of the account.The question of the nature and existence of possible worlds thus generally comes down to one's assessment of a given account's theoretical power and appeal.In his reply [5] to Pollock's article [6] in the Profiles volume dedicated to his work, Plantinga offers a proof of the existence of abstract possible worlds from relatively weak premises.More specifically, he argues for the proposition that (*) For any possible state of affairs.S, there is a possible world in which S obtains.If sound, this argument would provide a strong justification for believing in possible worlds, and would give Plantinga's conception of worlds a forceful *I would like to thank Jon Kvanvig and Hugh McCann for their comments on an earlier draft of this paper.