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. Some historical and intellectual background What is knowledge?
Review last lecture
Descartes’ Clear and Distinct Ideas
“The Trademark Argument”
The Cartesian Circle
Theories of Epistemic Justification
Some historical and intellectual background
What is knowledge?
Some puzzles and problems (Friday class)
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
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.
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
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
(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.
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?
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 (1612-1694) thought that there was serious problem with this argument – it appears to be circular:
Clear and Distinct Ideas
-Descartes appears to be committed to (see pp. 38-40)
(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)
-all knowledge-claims are ultimately justified by ideas/principles of reason
-all knowledge-claims are ultimately justified by ideas that originate in sensory experiences
-knowledge-claims do not require a foundation
-beliefs are justified by other beliefs
-no beliefs are basic or self-justifying
-knowledge-claims are NEVER justified