Anselm's Ontological Argument

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 then 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 ... .
... and this being thou art, O Lord, our God.
- St. Anselm, Proslogion (Translation by Sidney Norton Deane, 1903)

Can God's existence be proved logically? Many believers think, of course, that belief in God is a matter of faith, not logic. Many philosophers have thought the same thing. On the other hand, many believers think that there are good reasons and persuasive arguments for belief in God. Two such religious men, St. Anselm and St. Thomas Aquinas, who were also philosophers, offered logical proofs for God's existence which are still discussed and debated by contemporary philosophers and theologians.

St. Anselm's argument proceeds this way Conceive, if you will, of a being than which no greater can be conceived. Now, consider whether it is greater to exist or not to exist--to exist, certainly. But the atheist says that God does not exist. And yet, if he accepts the above statements (that God must be conceived as the greatest conceivable being, and that to exist is greater than not to exist) then he must conceive God as existing. Why? Because if he accepts that it is inconceivable to think of a greater being than God and yet he conceives God as not existing, he must admit that a God that existed would be greater. And that is the one that must exist!

So, if you conceive God correctly, you must conceive Him as existing. You do conceive Him. So He must exist! (The God that the atheist conceives of as not existing is not God.) Another way to put this proof is as follows: to say that God does not exist only makes sense if you understand what God is-- a being than which no greater can be conceived. But if you conceive of God as not existing, you have not conceived of that being than which no greater can be conceived; for a God that does not exist is not as great as a God that does exist. So if you conceive of God correctly, you must conceive Him as existing. That means He must exist.

St. Anselm's proof is very "Platonic" in that it moves from ideas in the mind to conclusions about what exists. With St. Thomas we will see an Aristotelian approach to proving God's existence, by way of evidence outside the mind.

But consider this counter-argument suppose you conceive of the perfect woman (a blend of Cybill Shepherd, Madeline Albright and Tina Turner, say). The mere fact that you conceive of such a woman does not prove that such a woman exists. And isn't this just like St, Anselm's argument? Is St. Anselm's argument really persuasive? Would it persuade a non-believer to believe in God?

Bibliography

Anselm, Anselm's Basic Writings, Open Court Publishing Company, LaSalle, Ill., 1962.

Copleston, F.C.. A History of Medieval Philosophy, Harper & Row, Publishers, New York, 1974.

Plantinga, Alvin (editor) The Ontological Argument, Anchor Books, Garden City, N.J., 1965.