[In this simplified form of the ontological argument for God’s existence,] God’s existence is deemed to be necessary because the concept of a non-existent God is taken to be in some way incoherent or self-contradictory.

The problem with this argument is evident as soon as we apply the same logic to something else, like the greatest athlete imaginable. If the greatest athlete imaginable doesn’t exist, then it seems we could imagine an athlete greater than this, namely the greatest athlete imaginable who does actually exists. This would make the non-existent greatest athlete imaginable not the greatest athlete imaginable after all. So it seems the greatest athlete imaginable must exist.

As should be clear, the same argument could apply to the greatest pizza imaginable, or the greatest symphony imaginable. Worse, it could also apply to non-existent entities. What about the greatest dragon or phoenix imaginable. Or the greatest half-man, half-cheeseburger imaginable?