Anselm's first argument
1. God = that than which nothing greater can be conceived.
2. Even a fool (atheist) understands, b/c admits in intellectu but not in re.
3. Greater to exist in both mind and reality.
4. Greatest conceivable being, if genuinely great, must exist in both.
5. T/f, since God is 'greatest conceivable being, must exist in both.
- Fool really a fool if denying existence of smth that is genuinely greatest (reductio ad absurdum).
Gaunilo of Marmoutier: On behalf of the Fool.
Counter-example of perfect island, structured similarly. If you imagine perfect island, must exist due to perfetion. No such island in existence unless found.
H/e; incoherent, as conceptions subjective in nature. No problems reflected in idea of perfect being = 3 O's.
Anselm's reply to Gaunilo/Second argument
God who cannot be thought not to exist > God who can be thought of as not existing
Idea of non-existent greatest conceivable being = contradictory.
2 types of existence:
Contingent: Islands etc. Depend on other physical things for existence. Changes may stop it from existing.
Necessary: Depends on nothing else - had to exist. Anselm believes Gaunilo's arg fails b/c God = necessarily exists.
Descartes's ontological argument
Revived after Aquinas' cosmological arg.
1. God is the supremely perfect being.
2. A supremely perfect being contains all supereme perfections.
3. Existence, (+ 3 O's), is a supreme perfection.
4. Conclusion (2 + 3) = God, a supremely perfect being, exists.
Relies on definition of God - existence essential property of perfect being.
'God exists' = true by definition.
Existence is a predicate - necessary.
Kant's first criticism
Even if existence is necessary predicate of God, doesn't mean God exists.
To accept a triangle but reject three angles = self-contradictory. But, if whole triangle is rejected, predicates are too, t/f, irrelevant. Applies to necessary being - rejected, predicates (existence) rejected, no contradiction.
Same point made earlier by David Hume:
what we can concieve existent, we can also conceive as non-existent.
Kant's second criticism
Existence is not a predicate. Predicates should tell us something a/b nature of obj/add something to its description. Saying 'exists' does not do this.
While Anselm's first argument cannot treat existence as a predicate, second can b/c of 'necessary'.
1) God is a supremely perfect being.
2) A supremely perfect being possesses every perfection.
3) Necessary existence is a perfection.
4) T/f, God possesses necessary existence.
5) God necessarily exists.
Maximally great being, only so if exists in every poss world.
M.G entails M.E incl. omnipotence, omniscience + moral perf.
1) There is a poss world in which there is a being that is maximally great.
2) If M.G, exists in our world.
3) Being has M.E, as M.G entails M.E.
4) So, there is a omnipotent, omniscient and morally perfect in our world.
5) There is a God.
Obj to this:
We are still only looking at the possibility, nothing in actuality. - Maximal excellence possible.
Anselm used 'exist' wrongly. Can't be predicate. Can be given to fictional things as well.
1) Donkey's exist.
2) Eeyore is a donkey.
3) Eeyore exists.
- Quite unsuccessful.
- Definitions limited - say things in terms of the possibility, not real.
- Difficulty in establishing definition for God - limited to finite human terms not adequate to describe God.