Abstract: In Ch.10, I apply the previous chapters’ account of modality to the Ontological Argument for the existence of God. I begin the chapter by attempting to develop a sound version of the Ontological Argument based on the work of St. Anselm. I conclude that this argument fails, as does a more recent attempt by Charles Hartshorne and Norman Malcolm. I then give a modal version of the Ontological Argument that is sound and is based on the claim that the property of unsurpassable greatness is possibly exemplified. I grant that this premise is not likely to be accepted by those who do not already hold that the property is actually exemplified, but I argue that it is still rational to accept the premise.

Keywords: Anselm, existence, God, Charles Hartshorne, Norman Malcolm, modal, Ontological Argument,