In class I’ve been talking about the ontological argument, one version of which runs like this:
Premise 1: God, by definition, is the greatest possible being.
Premise 2: A being which exists in reality is greater than a being which exists in the mind alone.
Conclusion: God exists in reality.
It’s pretty obvious to me that this is a bad argument, but I admit that, after years of occasionally thinking about and teaching this argument, it’s still not clear to me exactly where the argument goes wrong.
I know that the standard response is Kant’s, that existence isn’t a property, but it’s not clear to me that that really gets at the fundamental flaw of the argument. Suppose someone believed that existence is a property — suppose, to be more specific, that they believed in Meinongian objects, where there are both existent and non-existent objects. If that’s all that the person is wrong about, would such a person have to believe in the existence of God?
UPDATE: Even if Gaunilo’s objection is right, that you can (absurdly) give an argument analogous to the ontological argument to prove the existence of a perfect island, that still doesn’t show where exactly the ontological argument goes wrong, because all Gaunilo is doing is showing that the ontological argument goes wrong somewhere.