Lecture Notes: September 9

Intro to Course

I. What is philosophy?

A. love of knowledge
B. first and last of all disciplines
C. argument
D. search for truth

II. Core areas of philosophy

A. Epistemology
1. Theory of knowledge
2. What do we know?
3. How do we know it?
B. Metaphysics - What exists?
1. Physical world?
2. Numbers?
3. Souls?
4. Heaven?
5. Electrons?

III. Tools of philosophy: Logic

A. Argument: set of assertions that support a conclusion

B. Valid Deductive argument: if the premises are true, the conclusion must be true

C. Validity depends on form, not content

D. An argument:
1. All persons are mortal
2. Socrates is a person
3. So, Socrates is mortal

E. The same argument can be represented as:
1. All A's are B's
2. x is an A
3. :. x is a B

F. Which is related to:
1. If A then B
2. A
3. :. B

G. Which is called modus ponens and which can be written as:
1. If x is a person, then x is mortal
2. x is a person
3. :. x is mortal

H. Similarly, the following is called Modus Tollens
1. If A then B
2. not-B
3. :. not-A

I. Another valid form is Disjunctive Syllogism
1. Either McCall or Pataki will win the election
2. Pataki won't win
3. :. McCall will win

J. This can be symbolized as:
1. A or B
2. not-A,
3. :. B

K. or, similarly:
1. A or B
2. not-B,
3. :. A

L. Now notice that the following is a valid form:
1. All men are fish
2. Joe is a man
3. :. Joe is a fish

M. Since we don't like the conclusion, and the form is valid, we have to reject one of the premises.

N. Some Invalid argument forms:
1. Denying the antecedent
a. If A then B
b. not-A
c. :. B
2. Affirming the consequent
a. If A then B
b. B
c. :. A
3. For these, the conclusion can be false, and the premises true!

O. Basic logical Principle: Non-contradiction
1. not- (p and not-p)
2. something can't be both true and false
3. reductio proofs are based on this

P. Basic reductio form
1. Assume the negation of something
2. derive a contradiction (p and not-p)
3. conclude the affirmative of your assumption

Q. Much of what I will do will be to introduce an argument in this form.
If we don't like the conclusion, we will try to discover which of the premises are wrong.

IV. Soundness vs validity

A. Validity
1. concerns form of argument
2. 'p and not-p' is invalid, no matter what p is
3. first step in evaluating what someone says to you
4. does the conclusion follow?
5. example A)
a. If AIDS is harmless then we need not take precaution against it
b. AIDS is harmless
c. so we need not take precautions against AIDS
6. example B)
a. Any disease which threatens many lives is worth our concern
b. Mumps is worth our concern
c. so mumps threatens many lives
7. Both are bad arguments, but for different reasons
a. A) is valid, passes the first test
b. B) is invalid, we don't even have to go on to the second test

B. Soundness
1. concerns truth of premises
2. example A) is unsound - one of the premises is false
C. 2 questions you must answer for any philosophical argument:
1. is it valid? (i.e. does the conclusion follow from the premises?)
2. is it sound? (i.e. are the premises true)
Most important idea of all of this: If the conclusion of a valid argument is false, then one of the premises must be false

Transitivity of =, <, >, is
(1+1) + (1+1) = 2 +2
2 + 2 = 4
(1+1) + (1+1) =4

Theodore Geysel is Dr. Seuss
Dr. Seuss is the writer of The Cat in the Hat
The Cat in the Hat is a great book.
So, TG is the writer of a great book.

Consider:
God is love
Love is blind
Ray Charles is blind
So Ray Charles is God

Write in journals: What's wrong with this argument?

Intro to Descartes

Read Paragraph 1 of the Meditations

To get a sense of what Descartes is worried about, we have to do some history

Descartes (1596-1650)
'Father of modern philosophy' but still a medieval in many ways
revolutionary in thought, cleaving thought from sensation
Basic understanding of the world through Middle Ages derives from 2 sources

Aristotle (384-322 BC):
1) heavens are constant, earth is the center
2) causes are (partially) explained teleologically - by purposes. e.g. falling to the center

Ptolemy (2nd century AD): the sky is a thing (imagine it as a roof)
3) starry perfect spheres, perfect circles, etc.
4) 2 kinds of motion: on earth linear, in heavens circular

Not: the earth is flat, though that may have been a superstition
Note how these views cohere with a Biblical Judeo-Christian world view

Middle Ages:
dominance of church: king could jail you, etc. pope could send you to hell
heaven as outside spheres: hell, earth, heaven (with purgatory, etc)
teleology: the end (final cause) is always God

New science
15th century, new star discovered (telescope around 1609) (against 1)
Copernicus (1473-1543): hypothesized that earth was not stable, retrograde motion (against 1)
Brahe: planets move in ellipses (against 1 and 3)
Kepler (1571-1630): heliocentrism (against 1)
Galileo (1564-1642): Inquisition in 1633 for supporting Kepler
1 motion for all bodies, not one on earth and one in sky (against 4)
This is a unifying hypothesis, which explains all motion (against 2)
More than one center of motion (Jupiter's moons) (against 1)
Bumps on moon (against 3)
The earth has lost its place in the center of the world
this undermines the church's view, very dangerous

Direct attacks on religion
Weakening of church
Great Schism (1378-1417)
corruption
Henry VIII breaks with Rome, 1530
Luther (1483-1546) led Reformation, against selling indulgences, 95 Theses
Calvin (1509-1564) and the Protestant Work Ethic
Rise of individual against (earthly) central authority
humanism, reason
Aristotle on state as natural entity reborn

Rise of skepticism as a philosophy, due to loss of certainty of earth's place and due to Scriptural circularity:
Read from Letter of Dedication (The 'Please don't kill me' letter), paragraph 2
1) Why believe that God exists? - because it says so in the Bible
2) Why believe that the Bible is true? - because God wrote it
compare with:
1) what is philosophy? - what philosophers study
2) what do philosophers study? - philosophy
also:
Why believe that the crystal ball tells the truth? - because it says that it's true
The walls are tumbling, the church is in trouble

The times are not so different from our own
Increasing skepticism about religion and its explanatory role
Relativism, both metaphysical (no truth, it all depends on your perspective) and moral
Optimism about science and technology

Into this atmosphere comes Descartes
Discourse on Method, in French, 1637: popular and easy intro. You might take it in at your leisure.
Meditations, in Latin, 1641, with Objections and Replies (find in library)
Synopsis might be useful
famous mathematician, scientist
he wants certainty AND the new science
and he wants to replace Aristotle as 'the philosopher'
Q: can he have them? A: he needs to rebuild the foundations

read paragraph 1 of Meds
note: not mystical meditation, but based on reason
Goal is knowledge