Anselm's Ontological Argument

Here is the classical statement of the Ontological Argument from Anselm's (1033-1109) Proslogion, chapter two:

"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 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? . . . 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 nothing 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."

Now, don't anyone post a comment saying: "I can conceive of a Santa Claus, now a real Santa Claus is greater than an imagined Santa Claus, therefore Santa Claus must exist." This is not Anselm's argument even though I have seen people dismiss the argument with a similar statement. Anyone who reads the argument like this will surely NOT get a visit from Santa this year! Bear in mind that this argument has attracted the attention of many other philosophers who have presented their own version of it, including Aquinas, Descartes, Spinoza, Leibniz, Hegel, Hartshorne, Malcolm, Godel, and Plantinga.