1. Epistemology Revision
How does indirect realism lead to scepticism about the existence of the external world?

2. Epistemology Revision
Responses:
The external world is the ‘best hypothesis’ (Russell)
The coherence of the various senses and lack of choice over our experiences (Locke)

3. Philosophy of Religion
The ontological argument:
Descartes, hume and kant

4. Today’s lesson
You will learn how to explain Descartes’ ontological argument and criticisms from Hume and Kant

5. Homework due in
Outline and explain Gaunilo’s response to the Ontological Argument (9 marks)

6. Review of Learning What do the following terms mean? Ontos
Necessary existence
Contingent existence
A priori
A posteriori
Analytic statement
Synthetic statement

7. Task – 10 minutes
Explain Anselm’s argument for the existence of God and Gaunilo’s criticism of it
Create a visual answer to this question, using only symbols, pictures and a few key words

8. Descartes
Start by recalling what Descartes said about the piece of wax – what was his argument?
God is the only substance that has the power of sustaining itself in existence; everything else depends on God for its existence.
p.24

9. Descartes
‘The truth of these matters [concerning material bodies] is so open and so much in harmony with my nature, that on first discovering them it seems that I am not so much learning something new as remembering what I knew before; or it seems like noticing for the first time things which were long present within me although I had never turned my mental gaze on them before.’

10. Descartes
‘I have noticed certain laws that God has so established in nature, and of which he has implanted such notions in our minds, that after adequate reflection we cannot doubt that they are exactly observed in everything which exists or occurs in the world.’
He goes on to consider what he calls the immutable natures or immutable essences of particular things.

11. Triangles
What is a triangle?
What is a chiliagon?

12. So what is Descartes’ ontological argument?
Descartes inspects his idea of God, just as he inspected his idea of a triangle.
He finds that, just as a triangle has an immutable nature, so too does God.
Just as possessing three sides and angles that equal two right angles is part of the very nature of triangles, so too God possesses various immutable properties, one of which is existence.
p.24

13. So what is Descartes’ ontological argument?
The existence of God cannot be separated from the essence of God; existence is just part of what God is.
It would be a contradiction to think of a triangle that didn’t have three sides, and likewise it would be a contradiction to think of God not having the property of existence.
It is the essence of God to exist: God cannot fail to exist because he exists necessarily.
p.24

14. So what is Descartes’ ontological argument?
You might want to ask: Why is it the essence of God to exist?
Descartes’ answer is that God is perfect and existence is a perfection.
We must attribute all perfections to God and because existence is part of what it means to be perfect (just as Anselm argued), we must agree that God exists.

15. Predicates Predicates describe the characteristics of a thing E.g.
Tom is tall
Claire is intelligent
The chair is green
The rain is heavy
Descartes argues that existence is a predicate of God

16. Task – 10 minutes How is Descartes’ argument similar to Anselm’s?
How is it different?
Which philosopher do you think has the better argument?

17. Differences Anselm Descartes
No theory of absolute objective greatness – just a thought that existing in reality is greater than existing in the mind
A theory of absolute objective perfection – God is supremely perfect
No concept of total greatness, of which existence is an aspect
A concept of total perfection, of which existence is an aspect
Existence is not a predicate – it does not add to our concept of the subject
Existence is a predicate – it does add to our concept of the subject
Argues from a definition of God to the idea of his existence being ‘self-evident’
Demonstrates the existence of God in terms of mathematics
Shows that denying God’s existence involves a contradiction
Presents a causal argument – the concept of a perfect being must be caused by a perfect being

18. Discussion
Both Anselm and Descartes argue that it is contradictory to state that ‘God does not exist’ because existence is included in the very concept of God.
What do you think, is ‘God does not exist’ a contradiction?

19. Objections to Descartes
p.25-26
Hume:
‘All existential statements are synthetic’
Kant:
‘Existence is not a predicate’
The argument doesn’t prove that a perfect being actually exists

20. DVD – The Ontological Argument