REFLECTIONS ON THE LOGIC OF THE ONTOLOGICAL ARRGUMENT

Our 1991 paper on the logic of the ontological argument contained an analysis of the structure of Anselm’s argument for the existence of God. We showed that there is a valid argument for God’s existence in Proslogion II. However, in that paper, we deliberately decided not to include a discussion and analysis of the soundness of the argument. In these afterthoughts, we shall take up this question. We plan to argue for the following: 1. Anselm’s argument for Premise 1 is not valid. This casts doubt on the truth of Premise 1 of the ontological argument. 2. If Premise 1 is revised so as to be clearly true, and the rest of the ontological argument is modified so as to preserve validity with the revised Premise 1, then the resulting argument is sound but doesn’t have the conclusion that Anselm wishes to establish. Our analysis in what follows appeals to the theory of abstract objects (Zalta 1983) and to the distinction between exemplifying and encoding a property fundamental to that theory. Zalta 2004 uses this distinction to give a sympathetic reading of Anselm’s strategy in the Proslogion. We shall extend and refine that reading in what follows. WHY ANSELM’S ARGUMENT FOR PREMISE 1 IS INVALID If we take the theory of abstract objects as our starting point, then Anselm’s argument for Premise 1 is invalid. Anselm argues that there is something such that nothing greater can be conceived by appealing to the fact that we understand the definite description ‘that than which nothing greater can be conceived’. Anselm is implicitly relying here on the suggestion that the description in Premise 1 has an intension, namely, an intentional object existing in the understanding that serves as the content of the description. We actually agree with him on this point, and we also agree with his further supposition that this intentional object is such that nothing greater can be conceived. However, we