Ontological Argument: Anselm & Modal Logic

(Originally written February 22, 2007 in Book 13)

Arguments on behalf of the Ontological argument

1) It is conceivable that a being could exist in all possible worlds; If God didn't, he wouldn't be God.
2) Existence is predicated in the definition of God
3) There must be a cause for everything's existence or non-existence, so there is no reason why a necessary being couldn't exist.
4) Simpler hypothesis for God to exist in either all possible worlds or none
5) If God exists in all possible worlds, there is an answer to the question of why something exists rather than nothing. This is best answered by a necessary being.
6) If God can exist, he has to exist, or he wouldn't be God.
7) If we have any idea of perfection, there must be actual perfection, which is God.

The Ontological Argument

Anselm of Canterbury (1033 - 1109)

1) God is, by definition, that which nothing greater can be conceived.

Gaunilo

Objection 1: It does not follow that what exists in the mind exists in reality.
Objection 2: The mental formulation of the most perfect being is impossible.
Objection 3: If the ontological argument is valid then the existence of a perfect island can be inferred.

Latin word for being? Does it imply essence or existence? Does have multiple uses for the word as the word "being" does in English?

"Absolutely perfect" - refers to the essence of something.

Anselm: by definition all great-making qualities is in the absolutely perfect. All intrinsically great-making properties, not extrinsically.

The ontological argument is supposed to be completely a priori. But, you cannot have the ontological argument without presupposing the cosmological argument.

Modal Logic

If something is necessary it must be true in all logically possible worlds.

If something is possible, then it is true in at least one possible world.

If something is necessarily true it must be true in the actual world.

If something is possibly true then it may or may not be true in the actual world.

If it is possible that God exists, He necessarily does.