Gaunilo of Marmoutiers refuted Anselm of Canterbury’s argument by demonstrating a reductio ad absurdum of his own that, if the logic of the argument were applied to things other than God, it led to invalid conclusions. Now could it not with equal justice be said that I have in my understanding all manner of unreal objects, having absolutely no existence in themselves (Gaunilo of Marmoutiers)
Replacing the word ‘God’ with ‘the greatest island’ led to an argument which had the same form as Anselm of Canterbury’s, with true premises, and yet which leads to a false conclusion:
- I can conceive of an island that than which no greater island can be thought.
- Such an island must possess all perfections.
- Existence is perfection.
- Therefore, the island exists.
Even if ‘the greatest island’ were substituted for ‘the greatest possible island’ the argument would still lead to an invalid conclusion, since quite clearly to conceive of an island in all of its perfections does not guarantee its existence or bring it into existence.
There is always something more which can be added to make it more perfect, and our concept of perfection in islands, or other contingent things, is surely subjective - I cannot possibly guarantee that my perfect island is the same as yours.
1st Objection: Because the nature of God is mysterious, we do not have an idea of him - just a verbal symbol, not a conceivable thing.
2nd Objection: Just because you have an idea of a perfect thing, doesn’t mean that the perfect thing exists in reality.
| Gaunilo of Marmoutiers | Anselm of Canterbury’s response |
|---|---|
| We only have a verbal symbol, not a conceivable thing, for God | Proof doesn’t require complete understanding of God - only requires that we understand that God is such that no greater being can be conceived. |
| Just because you have an idea of a perfect thing, doesn’t mean that the perfect thing exists in reality. | God is not just the greatest thing of a certain type or the greatest thing of all. God is the being than which nothing greater can be conceived. |
- God is Causa sui
- Like Aristotle’s Uncaused Cause, God has no beginning and no end
- He cannot be caused by anything else
God’s existence is necessary
(Existence as in human existence, existing like a human not like anything else)
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For God to be God there must be more to Him than that he simply exists
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We exist, and that doesn’t make us God
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Therefore, God has to exist in reality or he would be too similar to us
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Humans have contingent existence. Mode of being which belongs to an object that happens to exist
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However, the object’s non-existence is equally conceivable. Something can exist or it doesn’t have to.
Necessary Existence
- Mode of existence of that which must exist at all times.
- An object that has to exist cannot not exist. That is illogical.
- It is self-contradictory to think of such an object:
- Coming into existence
- Being caused to be by anything other than itself
- To think of it being destroyed by anything other than itself ceasing to be.
Contingent vs Necessary
- A necessary being is infinitely superior as a mode of being that contingent existence.
- Because God is that than which nothing greater can be conceived, God is properly defined, it thus follows that God must be conceived as having necessary existence as the divine mode of being. But, the argument concludes, what has necessary existence must necessarily exist; therefore God exists.