Why does the Ontological Argument fail to prove the existence of God?

Answer 1

The Ontological Argument, first proposed by St. Anselm, consists of five propositions:

1. By the term "God" is meant a being than which none greater can be conceived.
2. Whether we affirm or deny the existence of God, a being than which none greater can be conceived exists in the understanding.
3. It is possible to conceive of a being than which none greater can be conceived existing not only in the understanding but in reality as well; and this is greater.
4. If, therefore, a being than which none greater can be conceived exists only in the understanding, it is not a being than which none greater can be conceived.
5. Therefore, a being than which none greater can be conceived exists also in reality.

Anselm's argument, as with similar ontological arguments raised by later theologians, fails because it is not a sound argument.

Bertrand Russell noted that "The argument does not, to a modern mind, seem very convincing, but it is easier to feel convinced that it must be fallacious than it is to find out precisely where the fallacy lies." David Hume demonstrated that fallacy: "[T]here is an evident absurdity in pretending to demonstrate a matter of fact, or to prove it by any arguments a priori. Nothing is demonstrable, unless the contrary implies a contradiction. Nothing, that is distinctly conceivable, implies a contradiction. Whatever we conceive as existent, we can also conceive as non-existent. There is no being, therefore, whose non-existence implies a contradiction. Consequently there is no being, whose existence is demonstrable." Hume was saying that if it is equally possible to conceive the non-existence of God, without a logical contradiction, then the ontological argument fails.

A parody of the ontological argument, that very well proves its absurdity is to to conceive of the greatest, or most perfect, island. As a matter of fact, it is likely that no such island actually exists. However, this argument would then say that we are not thinking of the greatest conceivable island, because the greatest conceivable island would existaccording to the ontological argument, since we can conceive of this greatest or most perfect island. No philosophical argument has ever proven the existence of God.