Transcript Critical Thinking - Western Washington University

Critical Thinking
Introduction
Arguments
 An argument is a series of statements, one
of which is offered as a statement to be
supported, and the rest of which are offered
as support.
 A conclusion is a statement to be supported.
 A premise is a statement that offers support.
Arguments
1) All dogs are mammals.
2) All mammals are animals.
3) [So] All dogs are animals.
Arguments
 Question: What do you do with witches?
 Answer: Burn them.
 Question: And What do you burn apart from
witches?
 Answer: Wood.
 Question: Does wood float in water?
 Answer: Yes.
 Question: What also floats in water?
 Answer: A duck.
Validity
 A valid argument is one in which it is
impossible for the premises to be true while
the conclusion is false—i.e., if the premises
are true, then the conclusion must be true as
well.
 An invalid argument is one in which it is
possible for the premises to be true while the
conclusion is false.
Validity
1) Rex is a dog.
2) All dogs are mammals.
3) [So] Rex is a mammal.
Validity
1) Rex is a dog.
2) Most dogs are pets.
3) [So] Rex is a pet.
Soundness
 A sound argument is a valid argument with
all true premises.
 An unsound argument is an argument that
is either invalid or has a false premise.
Arguments
1) All dogs are mammals.
2) All mammals are animals.
3) [So] All dogs are animals.
Fallacies
 A fallacy is a bad argument with the power to
persuade.
 False dilemma
 Straw Man
 Equivocation
False Dilemma
 A false dilemma is an argument that
presupposes there are only two options on
some issue, when in fact there are more.
False Dilemma
You are either building fences or you’re
learning Spanish.
-Stephen Colbert
September 26th, 2007
Either you are with us, or you are with the
terrorists.
-George W. Bush
September 20th, 2001
False Dilemma
1) You don’t support the War.
2) If you don’t support the War, you support
terrorism.
3) You support terrorism.
Straw Man
 A straw man is an argument that attacks a
misrepresentation of some view and then
concludes that the view is false.
1) The variety and complexity of life on earth
could not have arisen by random chance.
2) If that’s the case, then evolution is wrong.
3) Evolution is wrong.
Straw Man
You have perhaps noted that global warming
has struck Washington, hard. Since Gore
behind talking about this nonsense, the
weather has gone cold all over North
America: We’ve had record storms in the
Midwest; we have a record low temperature
right now at Washington, D.C., for this time of
year. So, everything seems to be say, God
seems to be saying “Gore is wrong!”
-Lyndon Larouche
Equivocation
 The fallacy of equivocation occurs when
someone uses the same word in two
different ways.
1) Man is the only rational creature.
2) Hilary Clinton isn’t a man.
3) [So] Hilary Clinton isn’t a rational creature.
Equivocation
 Dana Jacobson (on ESPN radio): I love
college football because every game matters.
 Desk Editor: Just try telling that to Boise St.!
They won every game and still got shut out of
the championship game!
Equivocation
There are 365 days in the year, but the average person
only works 8 hours a day. That’s one-third of a 24-hour
day. So the average person only works the equivalent
of one-third of 365 days—that is, about 122 days.
However, the average person doesn’t work on the
weekends. This means 2 days off a week. There are
52 weeks in a year, so there are 104 days off per year.
Subtracting this from 122 days leaves only 18 days.
But the average person gets at least this many days
off each year between holidays and vacation time. So
the average person doesn’t work at all.
Critical Thinking
 Critical thinking is the process of identifying,
explaining, and evaluating beliefs.
Critical Thinking
Critical reflection plays in important part in our growing
up, insofar as we come to think about ideas, beliefs
and attitudes that we have picked up along the way
from parents, teachers and friends. When we are
young we tend to absorb belief and attitudes
unthinkingly, and to that extent we are little more than
passive products of our environment. But is also
possible for us to think critically about them. We
many end up accepting or rejecting them, but
whatever position we end up with, it will be one that
we have decided for ourselves, for our own reasons.
-Falzon, “The Holy Grail”
Critical Thinking
[
Critical thinking] provides us with a way of
defending ourselves against manipulation
and control by others… we are no longer
simply at the mercy of whatever others tell us
to believe. We no longer take things at face
value. We can critically weigh up the positions
being presented to us, to see if there are in
fact good reasons for believing them.
-Falzon, “The Holy Grail”