René Descartes ( ) 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.

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.

Scepticism: Wave I The sceptic says: knowledge is impossible! Surely not! A mistake can only exist where there is truth or correctness. So, all that I believe could be false? A counterfeit £10 can exist because there are real ones. A counterfeit £15 note can’t. A test can only have wrong answers if there are right answers too. 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.

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

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

Descartes and the wax Consider a game like Call of Duty. All I see is a two- dimensional grid of pixels… 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. 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.

Descartes and God: The Ontological Argument 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. A real football is just as much a football as an imagined one. 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. So, we can’t say God has this property either. What makes God God are properties such as: …omnipotent. …omniscient. …omnibenevolent.