1. the ontological argument: an a-priori argument (ie, deductive rather than inductive)
Anselm
‘God’ is that being than which nothing greater can be conceived’; this idea exists in the mind, even of those who deny God’s existence (cf. Ps. 14:1); a being conceived of only in the mind would always be inferior to one existing in reality; therefore, that than which nothing greater can be conceived is God!

2. Background is in Plato’s thought
Think of the perfect circle!

3. For Anselm, God cannot be thought of as not existing: He is an eternal and necessary being, not limited by time.
All other beings and events (animals and the Big Bang, for example) are contingent entities;
Gaunilo disagrees – using the example of ‘the most perfect island’, he argues that for it to be ‘most perfect’ it must exist in reality, as well as in the mind;
Anselm: But an island can always be thought of as non-existent, having a beginning and end (and parts); but not God, who is unique, and not the same ‘thing’ as an island!

4. Gaunilo’s ‘On Behalf of the Fool’
His point is that Anselm’s argument cannot show that God necessarily exists (distinguish again between ‘necessity’ and ‘contingency’)
In other words, you cannot demonstrate the existence of something by simply having an idea about it – it is not possible to define the idea into existence.
Example: the ‘perfect island’

5. The Perfect Island Anyone can think of a most perfect island:
Beautiful palm trees, swaying in the breeze, waves breaking on golden waters etc.
He substitutes the words ‘greatest conceivable island’ for ‘greatest conceivable being’.
In other words, Anselm’s argument cannot even get off the starting blocks because human beings cannot conceive the nature of God.

6. Anselm’s Possible Replies
The island, while being the greatest possible island, does not have to exist – it is a ‘contingent entity’, but God is a ‘necessary being’.
However great an island is, there could always be one better – as there is no limit to what Gaunilio’s island could ‘contain’
In other words, Gaunilo is wrong to compare the ‘greatest possible being’ with the ‘greatest possible island’

7. ‘Existence is a predicate’
‘Predicate’ refers to an intrinsic quality – or property – that something has. In the case of a chocolate bar, for example, it will be shape and/or taste.
Anselm says that it is part of God’s nature that he should exist, that is, a predicate of God is His existence
In other words, the predicates of something are included in the subject you are talking about, and not:
‘Mrs. Smith is a widow whose husband has died’.

8. Anselm’s Second Version
The interesting thing is that this claimed to show that the non-existence of God was impossible, owing to the fact that any assertion of God’s non-existence must be self-contradictory.
In other words, God’s existence is said to be ‘necessary’

9. Anselm -summary
God is the greatest possible being which can be thought of.
God may exist either in the mind alone (‘in intellectuala’) or in reality (‘in re’).
Something which exists in reality and in the mind is greater than something that exists as an idea in the mind alone.
God, therefore, must exist.
For him, existence is a perfection which God cannot lack
Summary: God exists both in the mind and in reality. Why? Because He is a necessary being!

10. Descartes
He could no more think of God not existing than he could of a triangle without the angles being equal to two right angles!
In every human being, God has placed the idea of God (we are ‘stamped’ with it).
Some truths – 2+2=4, for example – cannot be doubted. It is similar with the idea of God’
It’s not really a matter of proving the idea of God to be true – really says that there is no good reason to doubt God’s existence.

11. ‘Triangles’
Triangles, by their very nature, have three sides and three interior angles, adding up to 180°.
Triangles are immutable, that is, incapable of change.
Even if we had no idea of a triangle, it is still this shape, with three sides!
And, like a triangle, God also has an immutable nature, and part of God’s nature is that He has existence.
In other words, as – Anselm – existence is a predicate of God.

12. Descartes’ notion of existence as perfection (page 112 of ‘Taylor’)
He argues that it is part of God’s nature to exist, and that this existence is perfection itself. Descartes means by this that something is not lacking in any way. He gives the example of it being impossible to think of a mountain existing without also the concept of the valley that goes with it.

13. Descartes contd. (‘Taylor’)
For Descartes, existence is a perfection of God, in the same way as a mountain and its valley must go together.
We cannot talk about God unless God exists, because God is perfect.
And part of being perfect is to have existence.
And that’s the crux of his argument, which he says we should simply ‘accept’

14. Kant’s Criticisms
Existence, he says, is not a predicate. We may have an idea of what is an unicorn (an imaginary white horse, with a long horn coming out of its forehead), but this does not mean that it exists in reality, even though we can think of unicorns as living creatures.
All statements about existence are, for Kant, by definition synthetic, that is, they need to be verified as true or false.

15. David Hume ‘All existential statements are synthetic’
What does he mean?
All statements about ‘existence’ must be capable of verification.
All cows are coloured ‘green’ Is this a synthetic statement?

16. Leaky Bucket Argument
In any ‘God question on the examination, make the point that, because these arguments are flawed, the larger the number does not make God’s existence any more likely – since the ‘water’ is still ‘leaking’.