On the Logic of the Ontological Argument

Abstract

Saint Anselm of Canterbury offered several arguments for the existence of God. We examine the famous ontological argument in Proslogium II. Many recent authors have interpreted this argument as a modal one.' But we believe Jonathan Barnes has argued persuasively Anselm's argument is not modal.2 Even if one were to construe the word 'can' in the definite description 'that than which none greater can be conceived' in terms of metaphysical possibility, the logic of the ontological argument itself doesn't include inferences based on this modality. In this paper, we develop a reading of Anselm's Proslogium contains no modal inferences. Rather, the argument turns on the difference between saying there is such a thing as x and saying x has the property of existence. We formally represent the claim there is such a thing as x by '3y(y=x)' and the claim x has the property of existence by 'E!x'. That is, we represent the difference between the two claims by exploiting the distinction between quantifying over x and predicating existence of x. We shall sometimes refer to this as the distinction between the being of x and the existence of x. Thus, instead of reading Anselm as having discovered a way of inferring God's actuality from His mere possibility, we read him as having discovered a way of inferring God's existence from His mere being. Another important feature of our reading concerns the fact we take the phrase that than which none greater can be conceived seriously. Certain inferences in the ontological argument are intimately linked to the logical behavior of this phrase, which is best