René Descartes

1. René Descartes The Father of Modern Philosophy

2. Cartesian Foundationalism & Dualism • Meditation I: ‘On what can be called into doubt’ • The search for foundations--how are beliefs justified. • What can I know? And how? • Meditation II: ‘The nature of mind which is better known than the body’ • The Mind-Body Problem • Descartes ontology

3. Born in La Hayein Touraine, a small town in central France, which has since been renamed after him • Introduced Cartesian geometry; through his laws of refraction, he developed an empirical understanding of rainbows; proposed a naturalistic account of the formation of the solar system… • His works were put on the Index of Prohibited Books. • Never married, but he did have a daughter, Francine, born in the Netherlands in 1635 (Francine’s mother was a maid in the home where he was staying). • He lived in the Netherlands for more than 20 years but died in Stockholm, Sweden, on February 11, 1650. Rene Descartes (1596–1650)

4. Descartes took a job tutoring Queen Christina of Sweden. It didn’t work out.

5. Descartes’ Milieu: The Scientific Revolution • Against Ptolemeic astronomy • Copernicus (1473-1543), Galileo (1564-1642), Kepler (1571-1630), Newton (1642-1727) • Mathematization • ‘Philosophy [i.e., physics] is written in this grand book—I mean the universe—which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics’ (Galileo) • The mechanical universe: against Aristotelian teleology of ‘substantial forms’ (‘final cause’)

6. Aristotle’s Universe

7. A Scientific Revolution: Ptolemy  Copernicus

8. Descartes Anti-Scholastic Program • Against explanation by reference to ‘substantial forms’: reject teleology (‘final cause’) as explanatory principle in favor of mechanistic explanation. • Teleology assumes mentality: stone doesn’t intend to fall to earth as a goal etc. • Against empiricism: Scholastics’ method was prone to doubt given their reliance on sensation as the source for all knowledge(from Aristotle’s empiricism) • Ideas of sensation aren’t ‘clear and distinct’ • Continental Rationalists vs. British Empiricists

9. Meditation I: On what can be called into doubt Descartes Meditation I

10. Knowledge Justified True Belief

11. What can we know…and what is knowledge??? • What is justification? • What is truth? • What is belief? The JTB Account: Knowledge as justified true belief

12. What is truth?

13. Belief A propositional attitude

14. Belief • We call beliefs ‘true’ or ‘false’ in virtue of the truth value of the propositions believed. • By ‘belief’ we don’t mean ‘mere belief’ • Believing doesn’t make it so - denial doesn’t make it not so. • We may believe with different degrees of conviction.

15. Propositions • The primary bearers of truth-value, the objects of belief and other “propositional attitudes” (i.e., what is believed, doubted, etc.[1]), the referents of that-clauses, and the meanings of sentences. • The ‘contents’ of thoughts • Sharable not private--since they make communication possible. • ‘Entertaining’, affirming, and asserting propositions • Descartes on Intellect and Will • Intellect entertains - Will affirms or denies propositions

16. Justification Having good reasons for what you believe

17. Foundationalism • Some beliefs are properly basic and that the rest of one’s beliefs inherit their epistemic status (knowledge or justification) in virtue of receiving proper support from the basic beliefs. • Foundationalists have two main projects: • a theory of proper basicality (that is, a theory of noninferential justification) and • a theory of appropriate support (that is, a theory of inferential justification). • The most well known foundationalist is Descartes, who takes as the foundation the allegedly indubitable knowledge of his own existence and the content of his ideas.  Every other justified belief must be grounded ultimately in this knowledge.

18. Descartes Quest for Foundations • Clearing the ground: the method of hyperbolical doubt (Descartes: ‘I only need to do this once’. • ‘preconceived opinions’ must be ‘set aside,” says Descartes, “in order to lay the first foundations of philosophy’ (1643 letter to Voetius, AT 8b:37). • The central insight of foundationalism is to organize knowledge in the manner of a well-structured, architectural edifice. • Foundation of unshakable first principles • Superstructure of further propositions anchored to the foundation via unshakable inference • Compare Euclid’s geometry

19. Descartes doubts… The program of Meditation I

20. Descartes’ Methodological Doubt None of these things are certain: • Empirical facts • Truths of mathematics • The existence of God I will apply myself earnestly and freely to the general overthrow of all my former ideas

21. Methodological Doubt: The Program • ‘I realized that if I wanted to establish anything in the sciences that was stable and likely to last, I needed—just once in my life—to demolish everything completely and start again from the foundations.’ • Method: withhold assent from any propositions that aren’t certain and indubitable. • We’ll consider beliefs by category: • Beliefs about ordinary objects gotten via sense experience • Mathematical propositions • Theological doctrine • Arguments aimed to show that none of these are certain… • The Argument from Sensory Illusion • The Dream Argument • The Evil Demon Argument

22. Sense Experience • ‘Ordinary objects’ • ‘Sense Experience’ • Veridical Experience: experience of real things as they really are • Non-veridical: illusions, mirages, dreams, etc. • Subject to methodological doubt: ‘Whatever I have accepted until now as most true has come to me through my senses. But occasionally I have found that they have deceived me… • Experience and judgement: can I avoid being mistaken under normal conditions if I’m careful, and not insane?

23. Argument from Sensory Illusion Our senses deceive us some of the time. Whatever can happens some of the time, possibly can happen all of the time. Therefore, It’s possible that our senses can deceive us all of the time.

24. Things are not always as they seem

25. Experience and judgement: Can we avoid being fooled? Müller-Lyer Illusion (interactive)

26. Parallel lines? The Café Wall Illusion in motion

27. What’s the illusion here?

30. Sense experience and judgement: expectation

31. We expect to see faces

32. We expect to see faces Face on Mars,Face in beans,...and more faces

33. Ambiguity Illusions

34. Figure-ground ambiguity

35. Rubin vase

36. More Rubin Illusions

37. And this

38. Autokineticeffect: illusions of motion • UFOs • Stepping Feet

39. Totally mad illusions!

40. Close up

41. The Greek version

43. Some dreams are so vivid that they seem real. Therefore, any waking experience could be a vivid dream.

44. Sense Experience: Dreaming • 'I am a man, and…I am in the habit of sleeping, and representing to myself in dreams those same things, or even sometimes others less probable, which the insane think are presented to them in their waking moments…At the present moment, however, I certainly look upon this paper with eyes wide awake; the head which I now move is not asleep…I cannot forget that, at other times I have been deceived in sleep….and, attentively considering those cases, I perceive so clearly that there exist no certain marks by which the state of waking can ever be distinguished from sleep, that I feel greatly astonished; and in amazement I almost persuade myself that I am now dreaming.’ • I realize that there is never any reliable way of distinguishing being awake from being asleep. This discovery makes me feel dizzy, [joke:] which itself reinforces the notion that I may be asleep!

45. Deep skepticism • Russell’s 5 minute hypothesis • The Brain-in-the-Vat hypothesis • Descartes Evil Demon

46. It was at that precise moment that Stanley realized that he may very well be a brain in a vat.

47. Solipsism Since I realized I created my own reality in every way, I must therefore admit that, in essence I was the only person alive in my universe. • The idea that ‘I alone exist’ and create all of reality • Should we prefer solipcism to the external world hypothesis?

48. Could all this be an illusion?

49. Could all of our experiences be non-veridical? I’m happy…what’s the problem?

50. Mathematics: More Certain? • So it seems reasonable to conclude that physics, astronomy, medicine, and all other sciences dealing with things that have complex structures are doubtful; while arithmetic, geometry and other studies of the simplest and most general things—whether they really exist in nature or not—contain something certain and indubitable. For whether I am awake or asleep, two plus three makes five, and a square has only four sides. It seems impossible to suspect that such obvious truths might be false. • Empirical sciences vs. math • A posteriori (empirical) and a prioriA posteriori (empirical) knowledge is based on experience, on observation of how things are in the world of changing things. A priori knowledge is based on reasoning rather than observation.