René Descartes (1596-1650)

1. René Descartes (1596-1650) • Father of modern rationalism. • Reason is the source of knowledge, not experience. • All our ideas are innate. • God fashioned us with these ideas. • We discover basic truths by intuition: by grasping basic connections between the ideas we have. • We deduce or demonstrate more complex truths.

2. Aim and method • Descartes wants knowledge. • He knows that he has many false beliefs. • He needs to weed them out to establish base of indubitable, necessarily true beliefs. • Foundationalism – basic beliefs provide the ultimate source of justification. • His method is to challenge each thing he believes to see whether it is “completely certain and indubitable”. This is known as the method of doubt. • Key reading – Ch. 4; Meditation 1.

3. Scepticism: Wave I What does this show? Simply that there is a reality and something we could have true beliefs about. But without a test, we can’t know which beliefs are true. So, there’s no way out of the sceptical problem here. The sceptic says: knowledge is impossible! So, all that I believe could be false? A test can only have wrong answers if there are right answers too. Surely not! A mistake can only exist where there is truth or correctness. A counterfeit £10 can exist because there are real ones. A counterfeit £15 note can’t.

4. Scepticism: Waves II and III The sceptic says: knowledge is impossible! …and so on, forever. So, even if there were a test, it would be of no use! Could there not be a test to prove whether I am in the Matrix? …but then how can I be sure I am really performing T*? I would need another test, T**… Let’s suppose so: a test T. I would need another test T* to check that I was performing the first test, T, correctly… I carry out T to determine whether I am in the Matrix… …or do I? How can I be sure I really did the test instead of being fooled into thinking I did it?

5. Cogito and Self Not reason that tells me – awarneess. I am a brain./

6. Descartes and the wax The Empiricist Hume will later argue that Descartes is wrong. All I can know are the surfaces of things: what my senses tell me. I simply come to believe that, despite changes in appearance, there is still the same wax because this simplifies my understanding of the world. Consider a game like Call of Duty. All I see is a two-dimensional grid of pixels… But my mind interprets certain arrangements of pixels as three-dimensional objects, even though there are no such things really there. In the same way, perhaps I interpret reality as a three-dimensional world of objects as this is a simpler explanation. It would be impossible to cope if I thought everything was always changing.

7. Descartes and God: The Ontological Argument A real football is just as much a football as an imagined one. Philosophers such as Gassendi, Kant and Russell claim this argument does not work. What makes (e.g.) a football what it is are properties such as being spherical and being bouncy. So, we can’t say God has this property either. What makes God God are properties such as: …omnipotent. A real football doesn’t have an extra property of existence. Existence isn’t a property. It doesn’t make anything the sort of thing it is. …omniscient. …omnibenevolent.