Ontological Argument no. 2

The flaws in Anselm's first ontological argument are exposed in Gaunilo's reductio ad absurdum argument found in "On Behalf of the Fool" arguing the existence of 'the perfect island'. He stated that the fact that the greatest conceivable being can be defined does not mean it exists. This is because intentional existence (i.e. having an idea of a perfect island) does not imply formal existence (i.e. that the island really exists in reality).

Can you prove that anything exists simply by defining them as the 'greatest'?

Gaunilo's criticisms led to Anselm refining his original argument by defining the nature of God's existence. He dismissed the analogy of the perfect island because no example taken from the world is comparable to God as they have contingent existence (i.e. they can be thought to exist or not). Whereas, God cannot have contingent existence or he would not be TTWNGCBC, and therefore he has necessary existence (i.e. cannot be thought to not exist). He concludes that not only the fact that God exists, but that he exists necessarily.

The ontological argument is frustrating because it was not designed to convince non-believers of God's existence and therefore you have to believe in God in order to understand and agree that the argument is valid. This leaves many criticisms of the argument meaningless because it never intended to satisfy those who did not love and have faith in God.
Hmmm..