Transcript Logical Fallacies

LOGICAL FALLACIES
English 11
REMEMBER…
 Only take notes on slides that have an arrow.
 You will be tested on these fallacies…TAKE GOOD NOTES.
LOGICAL FALLACIES
 logical fallacies are flaws in reasoning
that lead to faulty, illogical statements
 they are unreasonable argumentative
tactics named for what has gone wrong during
the reasoning process
LOGICAL FALLACIES
Often difficult to spot fallacies. They are
meant to manipulate readers by reaching their
emotions instead of their intellects.
WHY STUDY LOGICAL FALLACIES?
Learning to recognize these will:
Strengthen your own arguments
Help you critique other’s arguments
LIST OF MOST POPULAR FALLACIES
Ad hominem
Hasty Generalization
False Dilemma
Begging the Question
Post Hoc
Weak Analogy
AD HOMINEM – ARGUMENT TO THE PERSON
 An attack on the
person proposing an
argument rather than on the
argument itself.
 May attack a person’s
appearance, personal
habits, or character rather
than focusing on the merit
of the issue at hand.
 Reason: if something is
wrong with this person,
whatever he/she says must
be wrong.
AD HOMINEM: EXAMPLE
Sarah has never had a boyfriend for more
than a year, so whatever relationship advice
she gives you can’t be good.
Sara’s relationship status has nothing to do with the
quality of her advice.
HASTY GENERALIZATION
a conclusion based on insufficient or unrepresentative
evidence
 making assumptions about a whole group of range
of cases based on a sample that is inadequate
(stereotypes)
HASTY GENERALIZATION: EXAMPLE
The only redheads I know are rude. Therefore, all
redheads must have bad manners.
My roommate said her philosophy class was hard,
and the one I’m in is hard, too. All philosophy classes
must be hard.
FALSE DILEMMA
A false dilemma asserts that a complex situation can
have only two possible outcomes and that one of the
options is necessary.
 The arguer sets up the situation so it looks like there
are only two choices.
FALSE DILEMMA:EXAMPLE
The school building is in bad shape. Either we tear it down
and put up a new building, OR we continue to risk students’
safety. Since we shouldn’t risk anyone’s safety, we need to
tear down the building.
The argument doesn’t mention the possibility of repairing the
building. It acts as if there are only two options. Tear down building
or risk students’ safety.
BEGGING THE QUESTION
A kind of circular argument where the support only
restates the claim.
Asks the reader to accept the conclusion without
providing real evidence.
BEGGING THE QUESTION: EXAMPLE
Wrestling is dangerous because it is unsafe.
Jogging is fun because it is enjoyable.
Students should not be allowed to park in the lots reserved
for faculty because those lots should be for faculty only.
POST HOC
 The assumption that because one event follows
another, the first is the cause of the second.
 Assuming that because B comes after A, A
cause B.
POST HOC: EXAMPLE
President Jones raised taxes, and then the rate of violent
crime went up. Jones is responsible for the rise in crime.
Since Governor Jones took office, unemployment of
minorities in the state has decreased by seven percent.
Governor Jones should be applauded for reducing
unemployment among minorities.
WEAK ANALOGY
 when two things being compared aren’t really
alike in the relevant respects, the analogy is a weak
one
 comparing apples and oranges
WEAK ANALOGY: EXAMPLE
If we can put a man on the moon, why can’t we find the
cure for a common cold?
Guns are like hammers—they’re both tools with metal
parts that could be used to hurt someone.
FALLACY REVIEW
Grab a partner, a whiteboard, a dry
erase markers, and an orange eraser.
When you see the example…write down
the corresponding logical fallacy.
WHICH LOGICAL FALLACY IS THIS?
Plagiarism is deceitful because it is
dishonest.
WHICH LOGICAL FALLACY IS THIS?
Plagiarism is deceitful because it is
dishonest.
Begging the question
WHICH LOGICAL FALLACY IS THIS?
Water fluoridation affects the brain. Citywide,
student’s test scores began to drop five months after
fluoridation began. I think we know the cause.
WHICH LOGICAL FALLACY IS THIS?
Water fluoridation affects the brain. Citywide,
student’s test scores began to drop five months after
fluoridation began. I think we know the cause.
Post Hoc
WHICH LOGICAL FALLACY IS THIS?
I know three grad students who spend way too
much time studying. All grad students are
nerds.
WHICH LOGICAL FALLACY IS THIS?
I know three grad students who spend way too
much time studying. All grad students are
nerds.
Hasty Generalization
WHICH LOGICAL FALLACY IS THIS?
Supreme Court Justice Byron White was an AllAmerican football player while in college, so
how can you say that all athletes are dumb?
WHICH LOGICAL FALLACY IS THIS?
Supreme Court Justice Byron White was an AllAmerican football player while in college, so
how can you say that all athletes are dumb?
Hasty generalization
WHICH LOGICAL FALLACY IS THIS?
The book Investing for Dummies really helped me
understand my finances better. The book Chess for
Dummies was written by the same author, was published by
the same press, and costs about the same amount, so it
would probably help me understand my finances as well.
WHICH LOGICAL FALLACY IS THIS?
The book Investing for Dummies really helped me
understand my finances better. The book Chess for
Dummies was written by the same author, was published by
the same press, and costs about the same amount, so it
would probably help me understand my finances as well.
Weak Analogy
WHICH LOGICAL FALLACY IS THIS?
Look, you are going to have to make up your
mind. Either you decide that you can afford
this stereo, or you decide you are going to do
without music for awhile.
WHICH LOGICAL FALLACY IS THIS?
Look, you are going to have to make up your
mind. Either you decide that you can afford
this stereo, or you decide you are going to do
without music for awhile.
False dilemma
WHICH LOGICAL FALLACY IS THIS?
Justin Bieber can’t be a good musician. He
has been in and out of rehab too many
time.
WHICH LOGICAL FALLACY IS THIS?
Justin Bieber can’t be a good musician. He
has been in and out of rehab too many
time.
Ad hominem
#1
Josh’s iPhone broke after just two weeks, so
there must be something faulty in the general
manufacture of iPhones.
#2
I never listen to Eddie or take his advice
because he is a simpleton.
#3
You need to make a decision. Either you come
with us to the football game or you miss out on
a ton of fun this Friday.
#4
I ate three doughnuts for breakfast last Friday and
then I played the best badminton I have ever
played. Therefore, I need to eat three doughnuts
before every badminton match.
#5
Students shouldn’t get homework because they
don’t have time. They don’t have time for
homework so they shouldn’t get it.
#6
If you’re not afraid of haunted houses then you
shouldn’t be afraid of dark alleys. Both of
them are creepy, dimly lit, and have the
potential for someone to jump out at you.