In chapter 2 of Anselm’s Discourse On The Existence of God, Anselm set forth, what was later tagged, by Immanuel Kant, ontological argument, as follows:
[And] so, Lord, do thou, who dost give understanding to faith, give me, so far as thou knowest it to be profitable, to understand that thou art as we believe; and that thou art that which we believe. And, indeed, we believe that thou art a being than which nothing greater can be conceived. Or is there no such nature, since the fool hath said in his heart, there is no God? (Psalms 14:1). But, at any rate, this very fool, when he hears of this being of which I speak—a being than which nothing greater can be conceived—understands what he hears, and what he understands is in his understanding; although he does not understand it to exist.
For, it is one thing for an object to be in the understanding, and another to understand that the object exists. When a painter first conceives of what he will afterwards perform, he has it in his understanding, but he does not yet understand it to be, because he has not yet performed it. But after he has made the painting, he both has it in his understanding, and he understands that it exists, because he has made it.
Hence, even the fool is convinced that something exists in the understanding, at least, than which nothing greater can be conceived. For, when he hears of this, he understands it. And whatever is understood, exists in the understanding. And assuredly that, than which nothing greater can be conceived, cannot exist in the understanding alone. For, suppose it exists in the understanding alone: then it can be conceived to exist in reality; which is greater.
Therefore, if that, than which nothing greater can be conceived, exists in the understanding alone, the very being, than which nothing greater can be conceived, is one, than which a greater can be conceived. But obviously this is impossible. Hence, there is no doubt that there exists a being, than which nothing greater can be conceived, and it exists both in the understanding and in reality.(Anselm 2009:7-8)
Understanding God as that which none greater can be conceived, Alvin Plantinga outlined Anselm’s case as follows:
1) God exists in the understanding but not in reality.
2) Existence in reality is greater than existence in the understanding alone. (premise)
3) God’s existence in reality is conceivable. (premise)
4) If God did exist in reality, then He would be greater than He is. [From (1) and (2)]
5) It is conceivable that there is a being greater than God is. [(3) and (4)]
6) It is conceivable that there be a being greater than the being than which nothing greater can be conceived. [(5) by the definition of “God”]
But surely (6) is absurd and self-contradictory; how could we conceive of a being greater than the being than which none greater can be conceived? So we may conclude that
7) It is false that God exists in the understanding but not in reality.(Plantinga 1978: 87-8)
Question: How persuasive is Anselm’s case for the existence of God? What could be the possible objections to this version of ontological argument? Let the dialogue begin.
Anselm, S., Archbishop of Canterbury, & Deane, S. N. (2009). Proslogium; Monologium; An appendix, In behalf of the fool, by Gaunilon; and Cur Deus homo. Bellingham, WA: Logos Bible Software.
Plantinga,Alvin(1978) God, Freedom, and Evil. Grand Rapids: William B. Eerdmans Publishing Company