Lecture Three “The Problem of Knowledge” Think (pp. 32 – 48)  Review last lecture  Descartes’ Clear and Distinct Ideas  “The Trademark Argument”  The Cartesian Circle  Theories of Epistemic Justification

Review of Last Lecture I. Some historical and intellectual background II. What is knowledge? III. Descartes’ Meditations IV. Some puzzles and problems (Friday class)

Descartes’ Clear and Distinct Ideas  After reflecting on Cogito, Descartes convinces himself that ideas which he perceives clearly and distinctly must be true.  Descartes appeals to a mathematical model of clarity  Rationalism: emphasizes the importance of reason (instead of experience) to acquisition of knowledge  -a priori knowledge  Empiricism: Emphasizes the importance of sense experience to acquisition of knowledge  -a posteriori knowledge

An Example of an A Priori Proof About the World (from J. Brown, Laboratories of the Mind) This argument was offered by Galileo: According to Aristotle, heavier bodies fall faster than lighter bodies (H>L) -Suppose A and B are two balls, such that A is heavier than B. -Suppose that A and B are tied together by a long rope.

What will happen if A and B are released together? Since B falls slower than A (because A > B), A and B together will fall slower than A would. (B acts like a drag) But, since A and B together weigh more than A alone, they should fall faster than A would. (A+B > A) But this is impossible. Therefore, it must be false that heavier objects fall faster than lighter objects.

“The Trademark Argument”  This is an argument Descartes offers to show that God must exist.  Appeals to 2 principles about causation: If x causes y,  (1) There is always as much reality in x as there is in y  (2) x and y are co-temporal

Descartes distinguishes 2 kinds of reality: Formal Reality – Pertains to the world Objective Reality – Pertains to ideas With respect to ideas, Descartes’ view is that there must be as much formal reality in the cause of an idea as there is objective reality in the idea

The Argument: (1)I (Descartes) have an idea, x, of a being with all perfection. (2)That idea must have a cause, y. (3)Y must have as much formal reality as there is objective reality in x. (4)So, there exists something with at least as much formal reality as there is objective reality in my idea. (5)But that cause must be all-perfect (i.e. God) (6)Therefore, God exists.

Some Problems with “The Trademark Argument”  Why does Descartes think he is justified in holding his beliefs about causation? (These might be produced by Evil Demon)  Analogous arguments don’t seem persuasive (p. 35 Think)  Why does Descartes think he has a clear and distinct idea of a being with all perfections?

The Cartesian Circle Descartes feels that he now has two beliefs that are indubitable – that he exists and that there is a God with all perfections Since God has all perfection, He could not be a deceiver (deception would be an imperfection) Since God created him, Descartes feels that he can now be certain of the clear and distinct ideas he has In future, he must assent to only those ideas he perceives clearly and distinctly

Antoine Arnauld ( ) thought that there was serious problem with this argument – it appears to be circular: Clear and Distinct Ideas Clear and Distinct Ideas↨ God God -Descartes appears to be committed to (see pp ) (1)He can know that (CDp → Tp) ONLY IF he knows that God exists and is no deceiver (2)He can know that God exists and is no deceiver ONLY IF he knows that (CDp → Tp)

Theories of Epistemic Justification  Rational Foundationalism -all knowledge-claims are ultimately justified by ideas/principles of reason  Natural Foundationalism -all knowledge-claims are ultimately justified by ideas that originate in sensory experiences  Coherentism -knowledge-claims do not require a foundation -beliefs are justified by other beliefs -no beliefs are basic or self-justifying  Scepticism -knowledge-claims are NEVER justified