Rene Decartes

Rene Descartes - Rationalist

Ancient period – Greeks: Socrates, Plato, Aristotle

Modern period – begins with Descartes – “father of modern day philosophy”

Contemporary period – a.k.a. now, begun around 1890

Epistemology – theory of knowledge, belief, justification/evidence

- What do we know?

- What can we know?

- How do we come to know?

- What constitutes evidence or justification?

o Common epistemological questions

Descartes’ project: “To establish a firm and permanent structure for the sciences”

- Descartes wants to provide a foundation of certainty for the physical sciences.

Method of Doubt - Doubt everything! Withhold belief with respect to every proposition that you cannot be absolutely certain is true.

- Whatever is left after applying the method of doubt must be true. Those are the statements or propositions that can be used to build up the sciences.

Two kinds of propositions or potential beliefs

-a posteriori - based on information from the senses

- Obama is president, grass is green, roses are red…etc

-a priori – not based on sensory information.

- 2+2=4, geometrical statements, i.e., triangles have three sides, etc.

Skeptical arguments

1. If S doesn’t know not X, then S doesn’t know Y

2. S doesn’t know not X

3. S doesn’t know Y

Two specific skeptical arguments

1. Dream Argument – provides a reason to doubt a posteriori propositions

a. Let S be Descartes

b. Let X be Descartes is dreaming

c. Let Y be Descartes is sitting by the fire

Premises:

1) If Descartes doesn’t know that he’s not dreaming then he doesn’t know he’s sitting by the fire

2) Descartes doesn’t know he’s not dreaming

3) Descartes doesn’t know he’s sitting by the fire

2. The Evil Demon Argument – provides a reason to doubt a priori propositions

a. Let S be Descartes

b. Let X be being deceived by an evil demon

c. Let Y be 2+2=4

Premises:

1) If Descartes doesn’t know that he’s not being deceived by an evil demon, then he doesn’t know 2+2=4

2)...