Download Class #3

If I listened long enough to you
I’d find a way to believe that it’s all true
Knowing that you lied straight-faced while I cried
Still I look to find a reason to believe
Someone like you makes it hard to live without
Somebody else
Someone like you makes it easy to give
Never think about myself
If I gave you time to change my mind
I’d try to leave all the past behind
Knowing that you lied straight-faced while I cried
Still I look to find a reason to believe.
Someone like you makes it hard to live without
Somebody else
Someone like you makes it easy to give
Never think about myself
Rod Stewart, Reason to Believe
http://www.youtube.com/watch?v=zrjePH49Aq0
Philosophy 1010
Class #3
Title:
Introduction to Philosophy
Instructor:
Paul Dickey
E-mail Address: [email protected]
Reading Assignment for Next Week:
Velasquez, Philosophy: A Text With Readings Chapter 2.,
pp. 48-69.& pp 75-79.
Watch any movie listed below. Write a 3
paragraph (200-250 word) mini-essay
discussing one or two scenes in the movie and
how the scene(s) illustrate(s) a philosophical
view on the Nature of Man that is discussed in
Chapter Two.
Movie List: Schindler’s List (1993), River’s Edge
(1986), Leaving Las Vegas (1995), Blade Runner
(1982), Who is Julia? (1986), A.I.: Artificial
Intelligence (2001), Momento (2000), Total Recall
(1990), The Bourne Identity (2002), Bend It Like
Beckham (2002), My Big Fat Greek Wedding
(2002), The Long Walk Home (1990), Dark City
(1998)
Philosophy Applied:
Schindler’s List
Schindler’s List tells the true story of the German
businessman Oskar Schindler who comes to Nazioccupied Poland in hopes of using the abundant slave
labor force of Jews to manufacture goods for the
German military to make himself a fortune. By the end
of the film, he saves the lives of more than 1,100 Jews
by sacrificing his personal fortune.
While watching these film segments, consider views on
human nature that you will be reading about in chapter
two of the textbook:
e.g. Sigmund Freud, Thomas Hobbes,
Moritz Schlick, Aristotle, Jean-Paul Sartre
Logic and Critical Thinking:
An Overview
Video
The Fundamental Principle of Critical
Thinking is The Nature of an Argument
•
Making a claim is stating a belief or
opinion -- the conclusion
•
An argument is presented when you
give a reason or reasons that the claim
is true. -- the premise(s)
•
Thus, an argument consists of two
parts, and one part (the premise or
premises) is/are the reason(s) for
thinking that the conclusion is true.
Two Kinds of Good Arguments
•
A good deductive argument is one in which if
the premises are true, then the conclusion
necessarily (I.e. has to be) true.
•
Such an argument is called “valid” and
“proves” the conclusion.
•
For example – Julie lives in the United States
because she lives in Nebraska.
All men are mortal.
Socrates is a man.
____
Socrates is mortal.
•
A sound argument is a valid, deductive
argument in which the premises are in fact true.
Two kinds of good arguments
•
A good inductive argument is one in
which if the premises are true, then the
conclusion is probably true, but not
always. The truth of the premises do not
guarantee the truth of the conclusion.
•
Such an argument is called “strong”
and supports the conclusion.
•
For example: Craig lives in
Nebraska and he loves football, so
he is a Nebraska Cornhusker fan.
If offered to me before class today, I would
have made a bet with my wife that each of you would
sit in the same seat in class that you did last
Wednesday. If she would have taken the bet, would I
have won more money than I would have lost?
How Do We Evaluate an Argument?
Two ways (and only two ways) logically to
evaluate a claim –
1) Do the premises support or prove the
conclusion?
2) Are the premises true?
-- It would be illogical for you to argue, for
example, “I don’t want to believe that” or “You
just can’t say that”, or “Where did you come up
with that?” etc.
Ten Minute Break!
How Do Premises Support Conclusions?
For a Deductive argument, premises prove a
conclusion based on the logical form of the
statement.
Consider the argument:
(P1) If it’s raining outside, the grass is wet.
(P2) It’s raining outside.
_________________________
(Conclusion) The grass is wet.
In this case, the premises support the conclusion
fully simply by what the premises say. It would
be a contradiction to suggest that the conclusion
is false but the premises are true.
A. Categorical Arguments
•
Categorical Logic is logic based on the
relations of inclusion and exclusion among
classes.
•
That is, categorical logic is about things
being in and out of groups and what it
means to be in or out of one group by being
in or out of another group.
•
The following is a categorical syllogism:
(Premise 1) All Americans are consumers.
(Premise 2) Some consumers are not Democrats.
(Conclusion) Some Americans are not Democrats.
B. Hypothetical Arguments
“If it’s raining outside, the grass is wet. It’s raining
outside. Thus, the grass is wet.”
We often use variables to represent statements to
analyze arguments. In this case, say for example,
R = It’s raining outside; W = The grass is wet.
and “->” as if/then,
1) Thus we have an argument of the form:
R -> W
R
_____
W
This is the rule of modus ponens.
2)
“If it’s raining outside, the grass is wet. The
grass is not wet. Thus, it is not raining.”
R -> W
~W
_____
~R
This is the rule of Modus Tollens.
So what kind of an argument is this?
A good God would not permit evil to exist.
There is evil in the world.
____
Thus, a good God does not exist.
Say G = A good God exists, E= There is no evil in the
world.
Is this argument of the form:
If G  E
~E
_____
~G
If so, it is a valid deductive argument.
C. Chain Arguments
“If it’s raining outside, the grass is wet. If the grass
is wet, then our toddler will slip and fall. Thus, if it
is raining outside, our toddler will slip and fall.”
R -> W
W -> S
_____
R -> S
D. Disjunctive Arguments
“Either it is raining outside or else our toddler will
want go outside. Our toddler does not want to go
outside. Therefore, it is raining.”
R v G
~G
_____
R
How Do Premises Support Conclusions?
For an Inductive argument, premises support
(never prove) a conclusion based on how good the
premises provide evidence for the conclusion.
Consider the argument:
(P1) If it’s raining outside, the grass near the house
gets wet when the wind is not blowing strongly
from the North (which doesn’t often occur).
(P2) It’s raining outside.
_________________________
The grass near the house is wet.
Note: It would not be a contradiction to suggest
that the conclusion is false but the premises are
true.
How Does Sometimes
Our Thinking Crash?
Rhetoric
We are often influenced by rhetoric, language that is
psychologically persuasive but does not have pertinent
logical force.
There are many kinds of rhetorical deceptions or “devices”,
including:
hyperbole,
proof surrogates,
image rhetoric, and
euphemisms
Subjectivism
•
The view that “one opinion is as good as
another,” or “whatever is true is only what you
think is true” is subjectivism.
•
For some things, this makes sense. Does Miller
taste great?
•
To tell if something is subjective, ask yourself: “If
Curtis says “A” is true and Alicia says “A” is not
true, can they both be right?
•
One cannot give an argument either for or against
a subjective position.
•
Do you really want to say that whether God exists
is subjective? What about other philosophical
issues? Is what is real dependent on what your
friend thinks it is?
Logical Fallacies
Informal Fallacies occur when
standard expectations of
inductive logic are not followed:
1.
The rule of sufficient evidence is violated, thus
we have the fallacy of hasty generalization.
2.
The rule of use of all appropriate evidence is
violated, thus we have the fallacy of forgetful
induction.
3.
The rule of mistaking the meaning of sequence
(known as post hoc), thus we have the fallacy
of false cause. -- believing that one event caused
another just because they occurred at about the
same time. Billy’s grades began to dip at the same
time he stopped going to church, so it was not going
to church that caused his grades to drop.
4.
The rule of first understanding the argument
honestly before we evaluate it, thus we have
the straw man fallacy
•
The Straw Man Fallacy occurs when an argument is
distorted, exaggerated, or otherwise misinterpreted
such that it becomes easy or trivial to refute
•
In one of the 2008 Presidential debates, Gov.
Richardson responsed to Sen. Hilary Clinton’s
claiming herself to be an “experienced” candidate by
asking “So what is wrong with being a governor?”
Technically, this was a “straw man” characterization
of Sen. Clinton’s argument. He could have avoided
creating a straw man by asking something like “Is
being a governor less relevant experience than
being a Senator?”
Ten Minute Break!
Informal Fallacies also occur
when it is not recognized that the
purported premise is not even
relevant. (These are known as
“the fallacies of relevance”)
They include:
……
The Naturalistic Fallacy
•
This fallacy occurs when someone attempts to
derive a normative statement (what you “ought” to
do) from a descriptive statement (what “is” the
case).
For example, a student argues that the instructor
should excuse him from taking the mid-term
exam because he was sick.
Another example would be argue that the U.S.
military should remain in Iraq because they are
already there.
Another example could be to argue that simply
because God exists, you should act morally.
The Ad Hominem Fallacy
•
Maybe the most common of all logical mistakes.
•
The Ad Hominem Fallacy mistakes the qualities of the
argument itself with the qualities of the person making
the claim. Most Ad Hominem arguments are negative.
•
In an ad hominem, a person attacks the proponent of an
argument rather than analyzing the argument itself.
http://www.youtube.com/watch?v=9emz5hpxkrw
The Red Herring / Smokescreen
•
A red herring occurs when a topic or claim is introduced
that is irrelevant to the claim at issue with the intent only
of distracting the argument.
•
Similarly, a smokescreen is when topics or claims are
introduced that are irrelevant to the original issue with
the specific intent to make the issue appear to be too
complex or complicated to resolve.
Example: Senator, wait, before you vote on Bill 88.
do you realize that Delaware passed a bill on the
same subject in 1932, but it was ruled
unconstitutional for twenty reasons. Let me list them
here.... Also, before you vote on SB 88 you need to
know that .... And so on.
Wishful Thinking
•
Our hopes, desires and personal needs can delude
us and make us vulnerable to the fallacy of wishful
thinking.
•
We should always be able to recognize when analyzing
an argument what we want to believe and be sure that
our desires are not overriding our critical thinking and
making us come to conclusions simply because of what
“we want to believe.”
•
We may want to believe, for example, that God exists so
that we might feel more secure or happy. We must thus
separate that wish from the reasons that can serve as
premises for our claim that God exists.
•
You probably don’t want to believe this, but it is likely
true: http://www.scholarspot.com/video/11916/4415/Media-MultitaskersPay-Mental-Price
The Genetic Fallacy
•
The Genetic Fallacy suggests erroneously that a
claim is refuted by identifying its origin or history.
• e.g. The constitution is a bogus document since it
was primarily written with the intent to protect the
property of the wealthy.
• e.g. God does not exist because the whole idea of
God originated with superstitious people who had
no knowledge of all that we now have in science
about the universe and the human race.
• e.g. Religion is an “illusion” because it originates
from repressed, infantile needs (Sigmund Freud)
•Rush: “Like Rosie, you probably got really deep
issues from your childhood that need to be
resolved.”
Begging the Question
•
Begging the question is assuming as true the claim that
is at issue and is to be supported.
For example, God exists because the Bible says so and
we should believe what the Bible says because it was
written by God.
Another example:
An old gold miner’s joke:
One gold prospector asks the other: Why do you get
two pieces of gold for every one I get. The second
answers “Because I am the leader.” The first then
replies but why are you the leader? The second
responds: “Because I have twice the gold you do.”
Misplacing the Burden
•
The burden of proof in an argument rests on the person
making the claim. It is her responsibility to give the
premises and the reasons to believe her claim is true.
•
To try to shift the burden of proof onto the person who is
listening to your argument and trying to make him show
that you are wrong is called misplacing the burden of
proof.
•
A particular example of this logical error is the appeal to
ignorance which suggests that we should believe
something because no one has proven or shown it to be
wrong.
Informal Fallacies also occur when it
is not recognized that the purported
premise is ambiguous. (These are
known as “fallacies of ambiguity”)
These include:
Equivocation: changing meaning
between
premises and
conclusion.
Amphiboly : syntactical confusion
Composition/Division: attributing the
characteristics of part (or whole) to the
whole (or part).
4 Steps to Evaluating an Argument
1.
Be sure you understand the argument. What
is the claim? What are the premises for the
claim?
2.
Determine if the argument is deductive or
inductive and apply the appropriate test for
validity or strong support.
3.
Identify and weed out any logical fallacies,
rhetoric, subjectivity, or irrelevancies. Clarify
any vagueness or ambiguity.
4.
Examine the truth of the premises. If the
argument is inductive, evaluate the evidence.
Writing Assignment
Worth 10 points in Participation Category.
Review your answer to the question from the
first week of class. Evaluate your argument
(and if you wish improve it) based on the
principles of logic that we have discussed.
Can you now propose a better argument? Be
sure you state specifically what is your
claim/conclusion? Does the question you
asked still need to be clarified? What are your
premises or “reasons to believe”? Is your
argument deductive or inductive? If deductive,
is it valid? If inductive, is it strong?