1. Lecture 2 (Think, pp. 14 – 34) Descartes and the Problem of Knowledge: I. Some historical and intellectual background II. What is knowledge? III. Descartes’ Meditations IV. Some puzzles and problems (Friday class)

2. I. Some historical and intellectual background: Biographical Information about Descartes:  Born 1596 – Died 1650  Educated by Jesuits in the dominant Scholastic intellectual tradition  As mathematician, scientist and philosopher, he was central figure in Scientific Revolution of 17 th Century

3. The Scholastic Tradition:  Derived from writings of Aristotle (384-322 BC)  Aristotelian Science – Tried to explain natural phenomena by appeal to 4 types of causes:  Material Cause (what a thing is made of) “The ball bounced because it’s rubber.”  Formal Cause (How a thing is structured) “The ball rolled because it’s spherical.”  Efficient Causes (What brings something about) “The ball rolled because it was pushed.”  Formal Causes (What a thing’s purpose is) “The ball rolled because that’s what balls were designed to do.”

4.  Descartes and some contemporaries (Galileo) try to develop new approach to scientific understanding  Rejected “teleological explanations” (Aristotle’s Final Cause)  Try to explain world by appeal to laws, mechanical principles, and mathematics  Argued that all matter was the same throughout the universe  This was VERY controversial, since it was inconsistent with religious orthodoxy

5.  Descartes’ intellectual goal was to build a new and solid foundation for knowledge  Was an enormously grand conception or plan  Also, it was relatively dangerous (considering the period)  Descartes’ most famous work was entitled Meditations on First Philosophy In Which The Existence of God and the Distinction of the Soul from the Body Are Demonstrated (1641)  A series of 6 “meditations” in which Descartes tries to establish what it is, if anything, he can know for certain

6. II. What IS knowledge?:  Epistemology is the study of knowledge  What do we mean by the word “knowledge”?  When would we say that someone knows some proposition p?  They must believe p.  P must be true.  They must be justified in believing that p.  Thus, knowledge is (at a minimum) justified, true belief.  These are necessary conditions for knowledge.  Are they sufficient? (Gettier-type examples)

7. III. Descartes’ Meditations The project:  To clear away all false or doubtful beliefs  To establish a solid foundation on which he can build explanations about the world  The project involves what epistemologists call “a foundationalist” view about knowledge  Starting point is to determine which beliefs of his are or might be false  To this extent, Descartes begins with a strong sceptical position about knowledge

8. There are at least two methods that Descartes might have followed:  He might have examined each one of his beliefs in turn, and reject those that are false or doubtful  He might examine the commonsense principles which he has used to acquire beliefs about the world, and reject those that are not reliable  The first method is far to cumbersome  Descartes chose the second method

9. First Principle (of commonsense): (P1)The senses (sight, touch, smell,…) are our most reliable means of acquiring true beliefs about the world.  Descartes rejects (P1) and seems to offer the following as an argument- (1) Our senses sometimes deceive us (e.g. when the lighting is poor, or there are other “problems with the external circumstances). Therefore, (C)We should never trust our senses. (i.e. we should reject (P1))

10. But perhaps we can improve on (P1) as follows: (P2) When the external conditions are ideal, our senses are our most reliable means of acquiring true beliefs about the world.  But Descartes notes some problems associated with this principle  People who are delusional or insane often have hallucinations – their senses are not reliable sources of knowledge even when the external conditions are perfect  When he dreams, Descartes often misbelieves that what he is aware of is actually happening  Descartes argues that he has no way of being certain that he is sane or that he is not dreaming

11. So, Descartes is convinced that unless he can be sure that the external and internal conditions are right, he should not trust his senses as a source of knowledge.  He feels that he has no way to determine when the external and internal conditions are correct  So, he feels he should not use his senses as a guide to knowing about the world

12. Having convinced himself that the basic principles of commonsense (i.e. (P1) and (P2)) are false, Descartes then introduces one of his most famous pieces of reasoning, The Evil Demon Argument: (1) It is possible that there is an Evil Demon who systematically deceives me. (2) Unless I can be sure that there is no such Evil Demon, I should doubt ALL of my beliefs. (3) But I cannot be sure that there is no such Evil Demon. (4) Therefore, I should doubt ALL of my beliefs (i.e. I should be a sceptic)

13. Descartes’ Predicament:  By the end of Meditation One, he finds he is able to doubt everything.  This leaves him with basically nothing on which to construct new, more certain, beliefs.  He begins Meditation Two by reflecting again on what he thought he knew.  What he discovers is something quite remarkable…

14. “I think, therefore I am!”  This is known as Descartes’ Cogito “Cogito ergo sum” “Cogito ergo sum”  Essentially, what he discovers is that there is, as a matter of fact, one belief that he CANNOT doubt i.e. one belief of his that must be true i.e. one belief of his that must be true  Even the hypothesis of an Evil Demon will not cast doubt on the fact that insofar as he thinks, or doubts, he MUST exist. (Friday’s class – Some Problems and Puzzles raised by these arguments)

15.  Is justified, true belief sufficient for knowledge?  What is this self about whose existence Descartes is so certain? What kind of thing is it? How does he come to know it?  Does Descartes’ argument presuppose that some of our sense perceptions are true or “veridical” iv. Some puzzles and problems (Friday class)

16. Is justified, true belief sufficient for knowledge?  Some offer counter-examples in an attempt to show that these conditions are not sufficient (Gettier-type counter-example): Suppose that 1. Smith and Jones are candidates for the same job 2. Smith believes, with good reason, that Jones is better qualified 3. Smith knows that Jones has 12 stones in his pocket 4. Smith comes to believe, because of 2 & 3, that the person who will get the job has 12 stones in his pocket 5. Smith ends up getting the job 6. Unbeknownst to Smith, he also had 12 stones in his pocket Question: Did Smith know that the person who will get the job has 12 stones in his pocket

17. What is this self about whose existence Descartes is so certain? What kind of thing is it? How does he come to know it?:  A thinking thing (res cogitans)  Not extended, not material, a thinking substance (not a material substance)  Knowledge of the self is not dependent on his knowing anything about bodies/(matter) that exist(s) Descartes can doubt whether he has a body Descartes can doubt whether he has a body He cannot doubt that he exists He cannot doubt that he exists Therefore, Therefore, What justifies his belief that he exists is independent of material things What justifies his belief that he exists is independent of material things

18.  The point of Descartes’ discussion about piece of wax is supposed to show that bodies, like his mind, are also perceived by the intellect (not the senses)  Descartes’ argument for the distinctness of mind and matter would be flawed if it were the following: 1) I can doubt whether I have a body. 2) I cannot doubt that I exist. Therefore, 3) I am ≠ my body  This would be an instance of The Masked Man Fallacy Compare: 1) I doubt whether Samuel Clemens was American. 2) I don’t doubt that Mark Twain was American. Therefore, 3) Samuel Clemens ≠ Mark Twain

19.  Does Descartes’ sceptical argument presuppose that some of our sense perceptions are true or “veridical”?  When he says that he knows some of his perceptions have been false/misleading, this might suggest that he knows that other perceptions are true or veridical.  But this is not the only (or most charitable) way to understand his argument.  He may be appealing to the fact that in the past his beliefs based on sensory evidence have been inconsistent he would, thus, know that not all of them could be true (but all could be false). he would, thus, know that not all of them could be true (but all could be false).

20.  Next class – Read the rest of Chapter 1 - Re-read the first half of Chapter 1 - Re-read the first half of Chapter 1  Lecture notes WILL be posted on course web page www.ryerson.ca/~ahunter/PHL201/