Transcript Logical fallacies

Logical fallacies
FALLACY
A MISTAKE IN REASONING; A DEFECT
IN AN ARGUMENT
Two Types:
• Formal - a defect in the form or
structure of an argument
• Informal - a defect in the content,
material, or the language of the
argument
An argument is like a building.
Just as a building has a structure and
is made out of material, so too does
an argument have a structure and is
made out of material.
The material of an argument is the
language.
Our focus is on informal fallacies.
Such fallacies are committed with the
intent to deceive. Keep in mind that the
person best able to deceive you - to make
his or her argument appear good - is the
person who knows these fallacies. Also
keep in mind that though the argument
may appear to be good, it is not in fact a
good argument but a fallacious one.
Appeal to Force
• Using the threat
of physical or
psychological
force to make
your opponent
concede to your
position.
There are two types of Appeal to
Force
Appeal to Physical Force
• Use the threat of physical harm to
make your opponent concede to
your position.
• This threat can be either against
their person or their property.
Examples
• Agree with me or I will punch you
in the nose. Now don’t you see why
you should agree with me?
• Mrs.Lodato, I think that I should
receive an ‘A’ in this class. I know
you will agree. By the way, I know
where you live.
Appeal to Psychological Force
• Use the threat of psychological
damage to your opponent to get
them to concede to your position.
Examples
• If you do not support your local
charity you will burn in hell.
Therefore, you should support it.
• Mrs. Lodato, I think I should
receive an ‘A’ in this course. I
know you will agree. By the way,
my father is on the Board of
Directors of this college, and he
does everything I tell him to do.
Appeal to Pity
• Here you appeal to
your opponent’s
sympathy to make
them concede to
your position.
• That is, you attempt
to make your
opponent believe
that you will be
miserable unless
they concede to your
position.
Examples
• Student to teacher: You should let me
take the exam over, because if I do not
pass this course, my mother will never
forgive herself, my father will not speak
to me, and even the dog will hate me.
• Lawyer to jury: Please let my client go.
Sure he committed the murders, but it
wasn’t his fault. He had a bad
childhood. His mother left him when he
was 18 and someone stole his puppy
when he was 19.
Bandwagon
• Here you argue that
since everyone is
doing something,
your opponent
should do it too,
otherwise he or she
will be left out and
not fit in with the
crowd.
Examples
• Everyone enjoys smoking Whiz, so
you should too
• Don’t be left out in the cold. Come
on in and have a Schlitz!!!!
Appeal to Vanity
• Here someone tells you that if you
use a certain product or accept a
certain point, you will be admired
and sought after like a celebrity
who is said to use the product.
Examples
• Liz Taylor uses Passion perfume,
and young, naked men are after
her. If you use Passion, young and
naked men will be after you.
• Michael Jordan wears Nikke
basketball shoes. If you wear
them, you will play like Michael!!!!
Abusive/Namecalling
• Here you specifically
attack the person
under question by
calling him or her a
name
Examples
• You should not vote for Al Gore because
he is a ‘liberal’ and will be after your
wallet.
• You can’t trust Joe because he has
shifty eyes
• Why should we believe you? You have a
beard, you smoke cigarettes, and you do
not have a job.
Tu Quoque
‘You Too’
‘Two Wrongs Make A Right”
• This fallacy is
committed when a
speaker, trying to
show that he is not
at fault, argues that
his opponent has
said or done things
just as bad as he,
the speaker, has
been accused of.
Examples
• Son to father: Sure I smoke dope dad,
but you drink and that is just as bad.
• Daughter of mother: I should be
allowed to date at age 12. You got
married when you were 16.
• Politician: Sure I have made mistakes,
but candidate X has admitted to
committing adultery.
Misplaced Authority
• This fallacy is committed when
testimony from an authority is
used as evidence in an argument,
but the authority quoted is not an
authority in the field under
discussion.
Examples
• Wear Leggs pantyhose. Joe Namath
says they are comfortable
• Psychologist to jury: The defendant
does not suffer from schizophrenia. I
ought to know, I have a Masters degree
in Grief Therapy.
• Our foreign policy needs revision. Just
look at the experts who support my
view: Miss Piggy, fifteen logic
professors, and five taxi cab drivers.
Appeal to Tradition
This fallacy is committed when it is argued that
because something
was done a certain way in the past, it should continue
to be done that way.
Examples
• Women should not work outside
the home. My mother did not
work, my grandma did not work,
and neither will you.
• What do you mean I need to
change my History text? I have
been using this text for the past 50
years and I will continue to use it.
Who cares if it is out of print?
Hasty Generalization
• This fallacy is
committed when
the reasoner
‘rushes to
judgment’ or a
conclusion based
on too little
evidence.
Examples
• The first two apples I took out of
that barrel had holes in them, so
probably all of the apples in that
barrel have holes in them.
• He must be poor. He has a beard
and is wearing dirty clothes. We
should give him some money.
Black or White
• This fallacy is committed
when you argue that
since you opponent
doesn’t agree with your
position, then he must
agree with the extreme
of your position. You try
to make you opponent or
audience think that there
are only two choices
(yours and the extreme),
when in fact there are
many.
Examples
• So you don’t think that prisoners should
be allowed to watch cable. Well, you
would have them all in isolation, and
eating nothing but bread and water.
• You don’t believe in buying diamonds
for Valentine’s Day? Well, you must
think that all women are just here to
serve and slave for you.
Slippery Slope
• Here it is argued that if
one event is allowed to
occur, then a whole
series of consequences
will also occur. Or if
you accept one point,
then you must accept a
series of other points.
The consequences may
be either good or bad.
Examples
• Mother to daughter (who is on a diet): “If
you eat that donut, then you will eat the
whole box, and then you will gain back all of
your weight, and then you will have to buy all
new clothes and and a new car, and you will
never get married.
• Mother to daughter: If you lose weight, you
will become a beauty queen, and then a
movie star, etc.
Begging The Question
• This fallacy occurs when the arguer
presents evidence for the conclusion,
but the evidence is either opinion or
there is no proof offered that the
evidence is true.
Examples
• To be a good president you have to
have at least 30 years of experience.
• To be a good student you must study at
least four hours per night.