Descartes & Lehrer

(Originally Written September 8, 2006 in Epistemology)

Descartes:

-Methodological doubt
-dream argument
-evil genius argument

External World
Senses
God
Cogito

The Cogito is the foundation

A major problem with Descartes' theory is that he uses logic/reason to move from the cogito to God, but he uses the existence of God to show that logic/reason is reliable.

Keith Lehrer

"We don't know anything" (This is not a knowledge claim)

A priori knowledge - known independently of experience
A posteriori knowledge - known through experience
Logically necessary truth - one that can't be false, truths true by definition, tautologies, etc.
Contingent truth - something that is true, but could've been false

Lehrer denies that we know logically necessary truths. He denies that, although they have true beliefs, they have no justification for their beliefs, and thus no knowledge.

A major problem with this is that while some people cannot give justifications for logically necessary truths, others can.

Lehrer denies the existence of contingent truths because we are capable of misidentifying things.

Lehrer uses Descartes definition of knowledge which states that to know something one must be absolutely certain.