Latest version of my SEP entry on ontological arguments, which first appeared in 1996. General discussion of ontological arguments. Includes a brief historical overview, a taxonomy of different kinds of ontological arguments, a brief survey of objections to the different kinds of ontological arguments identified in the taxonomy, and more extended discussions of Anselm's ontological argument (Proslogion 2), Godel's ontological argument, and Plantinga's ontological argument.

Oppenheimer & Zalta have re-formulated their non-modal version of the ontological argument, with the help of PROVER9, an automated reasoning engine. The authors end up rejecting the new argument; however, the theist has a rejoinder worth considering. But after presenting the rejoinder, I highlight that the conceivability of the being does not imply its possibility. One lesson is that even non-modal ontological arguments must engage modal matters concerning God. Another lesson is that if PROVER9 is able to derive a conclusion (...) from fewer premises, the proof is sometimes inferior as an argument. (shrink)

This paper attacks the modal ontological argument, as advocated by Plantinga among others. Whereas other criticisms in the literature reject one of its premises, the present line is that the argument is invalid. This becomes apparent once we run the argument assuming fictionalism about possible worlds. Broadly speaking, the problem is that if one defines “x” as something that exists, it does not follow that there is anything satisfying the definition. Yet unlike non-modal ontological arguments, the modal argument commits this (...) “existential fallacy” not in relation to the definition of ‘God’. Rather, it occurs in relation to the modal facts quantified over within a Kripkean modal logic. In brief, we can describe the modal facts by whichever logic we prefer—yet it does not follow that there are genuine modal facts, as opposed to mere facts-according-to-the-fiction. A broader consequence of the discussion is that the existential fallacy is an issue for many projects in “armchair metaphysics.”. (shrink)

Inspired by the third chapter of Anselm's Proslogion, twentieth century philosophers including Charles Hartshorne and Alvin Plantinga developed “modal” ontological arguments for the existence of God. Such arguments use modal logic to infer God's existence from the premises that (i) God's existence is possible and (ii) if God exists, He exists necessarily. Like other ontological arguments, modal arguments have won few converts to theism; many commentators consider them question‐begging or liable to parody. This article details how recent attempts to defend (...) these arguments have tried to overcome these difficulties by drawing on modern accounts of the epistemology and metaphysics of modality. (shrink)

By defining God as a maximally great being Plantinga is able to devise an ontological argument which validly infers from the possibility of there being a God that there necessarily is a God. In this article I shall argue that Plantinga’s argument is not only question-begging, as several critics have complained, but circular in the strongest sense of the term. Based on reflections on the relation between the notions of coherence and possibility, I shall defend two arguments, previously proposed by (...) Tooley and Guleserian, against the existence of a maximally great being. The article concludes with some critical remarks on Plantinga’s rationale for conceiving God as such a being. (shrink)

This article is a presentation of Plantinga’s ontological argument in its historical and systematical frames. Criticisms of the argument are presented as well. Philosophical claims underlying the defense of the argument are described as minimalist, but their connection with a strong logical system is noted.

My aim in this paper is to critically assess Plantinga’s modal ontological argument for existence of God, such as it is presented in the book “The Nature of Necessity”. Plantinga tries to show that this argument is valid and it is rational to believe in his main premise, namely “there is a possible world in which maximal greatness is instantiated”. On the one hand, I want to show that this argument is logically valid in both systems B and S5 of (...) modal logic. On the other hand, I think that this argument is not a good argument to show that God exists or that it is rational to believe in God. (shrink)

Calvin famously interprets Romans 1 as ascribing human knowledge of God in nature not to inferences from created things (natural theology) but to a “senseof deity” that all people share and sinfully suppress. I want to suggest that the sense of deity interpretation actually provides the resources for explaining thepersuasive power and usefulness of natural theology. Specifi cally, I will argue that understanding certain ontological and cosmological arguments as dependenton the sense of deity preserves their ability to persuade while helping (...) solve serious problems with the justifi cation of their premises. In the case of the ontological argument, this will provide a new response to the most serious objection that the argument faces, the charge that it begs the question. (shrink)