1Credo ut intelligam — I believe that I may understand.
2 There are various ways to express the versions of this argument. One straightforward one might be:
We all have an idea of God.
We can define this as a being greater than which cannot be conceived.
Either this being exists in our mind alone or it exists in reality as well.
If this being exists only in our mind then it is not a being greater than which cannot be conceived for a being that exists in reality must be greater than a being that exists only in our mind.
It would be absurd to say this being exists only in our mind (reductio ad absurdum).
Therefore God exists.
3 This is a mode of argumentation that seeks to establish a contention by deriving an absurdity from its denial, thus arguing that a thesis must be accepted because its rejection would be untenable. It is central to Anselm’s argument.
4 An example of a tautology would be to say ‘all wet things are wet’. In the same way, Anselm believes that the word ‘God’ contains the meaning ‘exists’. So, for Anselm, ‘God exists’ is a tautology.
5 Gaunilo of Marmoutiers set out to produce a parallel argument aimed at demonstrating that the existence of any perfect thing could be constructed.
He suggested that his readers think of the greatest, or most perfect, conceivable island.
As a matter of fact, such an island is unlikely to exist.
However, he goes on to say that we are not thinking of the greatest conceivable island, because it would exist, having all desirable qualities.
6 Something that has contingent existence by definition depends on something else for its existence. So in terms of this, an island depends on all sorts of things that make its existence contingent.
7 Anselm’s second argument has at its heart the philosophical understanding of ‘necessary existence’. In this context necessary means ‘cannot not be’ as opposed to contingent, meaning ‘can cease to exist’. He argues:
We define God as a being than which none greater can be imagined.
A being that necessarily exists in reality is greater than one that does not necessarily exist.
By definition, then, if God exists as an idea in the mind but does not necessarily exist in reality, we can think of something that is greater than God.
But we cannot think of something that is greater than God.
Thus, as God exists in the mind as an idea, then God necessarily exists in reality.
Therefore God necessarily exists in reality.
8 ‘…is in itself self-evident, because God is his own essence.…because we do not know the essence of God the proposition is not self-evident to us, but must be demonstrated by things that are known more to us, though less evident in themselves — namely by his effects.’
9 Again there are a number of ways to answer this question. One straightforward one is: