This chapter contains sections titled: The Validity of Anselm's Ontological Argument The Truth of the Anselmian Premises On Whether Anselm's Ontological Argument Begs the Question On Parodies The Validity of the Ontological Argument of Descartes and Leibniz On the Truth of the Descartes–Leibniz Premises Critiques of the Descartes–Leibniz Ontological Argument Ontological Arguments of the Twentieth Century Gödel's Ontological Argument On Whether Gödel's Argument is Sound The Modal Perfection Argument The Temporal‐Contingency Argument Conclusion References Appendix 1. Logic Matters Appendix 2. Formal (...) Proofs of Some Modal Arguments. (shrink)

The Modal Perfection Argument (MPA) for the existence of a Supreme Being is a new ontological argument that is rooted in the insights of Anselm, Leibniz and Gödel. Something is supreme if and only if nothing is possibly greater, and a perfection is a property that it is better to have than not. The premises of MPA are that supremity is a perfection, perfections entail only perfections, and the negation of a perfection is not a perfection. I do three things (...) in this paper. First, I prove that MPA is valid by constructing a formal deduction of it in second order modal logic. Second, I argue that its premises are true. Third, I defend the argument and the logic used against some likely objections. (shrink)

This paper is a reply to Graham Oppy’s “Maydole’s 2QS5 Argument,” published in Philo 7, 2 (2004). I argue that he fails to refute myModal Perfection Argument for the existence of a Supreme Being, and that it remains arguably sound in the face of his alleged counterexamples and parodies.

The Third Way is the most interesting and insightful of Aquinas' five arguments for the existence of God, even though it is invalid and has some false premises. With the help of a somewhat weak modal logic, however, the Third Way can be transformed into a argument which is certainly valid and plausibly sound. Much of what Aquinas asserted in the Third Way is possibly true even if it is not actually true. Instead of assuming, for example, that things which (...) are contingent fail to exist at some time, we need only assume that contingent things possibly fail to exist at some time. Likewise, we can replace the assumption that if all things fail to exist at some time then there is a time when nothing exists, with the corresponding assumption that if all things possibly fail to exist at some time then possibly there is a time when nothing exists. These and other similar replacements suffice to produce a cogent cosmological argument. (shrink)

This paper is a reply to Graham Oppy’s “Maydole’s 2QS5 Argument,” published in Philo 7, 2 (2004). I argue that he fails to refute myModal Perfection Argument for the existence of a Supreme Being, and that it remains arguably sound in the face of his alleged counterexamples and parodies.