Transcript Informal Fallacies - Long Beach City College

Fallacies
Flaws in the Structure of an Argument
What are fallacies?
Fallacies are defects in an argument that
cause it to be invalid, unsound, or weak.
 Fallacies can be separated into two
general groups: formal and informal.

Formal Fallacies

Formal fallacies are only found in deductive arguments.

Deductive arguments are supposed to be air-tight.

For a deductive argument to be valid, it must be
absolutely impossible for both its premises to be true
and its conclusion to be false. With a good deductive
argument, that simply cannot happen; the truth of the
premises entails the truth of the conclusion.
Formal Fallacies

The classic example of a deductively valid
argument is:
– 1. All men are mortal. (premise)
– 2. Socrates is a man. (premise)
– 3. Therefore Socrates is mortal. (guaranteed conclusion)

It is simply not possible that both (1) and (2)
are true and (3) is false, so this argument is
deductively valid.
Formal Fallacies

Any deductive argument that fails to meet this very high
standard commits a logical error, and so, technically, is
fallacious.

This includes many arguments that we would usually
accept as good arguments, arguments that make their
conclusions highly probable but not certain.

Arguments that aren’t deductively valid are said to
commit a “formal fallacy.”
Formal Fallacies

Example of a deductive argument with a formal fallacy:
1. All humans are mammals. (premise)
2. All cats are mammals. (premise)
3. All humans are cats. (conclusion)

Both premises in this argument are true but the
conclusion is false. The defect is a formal fallacy and can
be demonstrated by reducing the argument to its bare
structure:
1. All A are C
2. All B are C
3. All A are B
Formal Fallacies

With deductive arguments, it can be
helpful to reduce an argument to its
structure.
– All chickens are feathered animals. (premise)
– Clucko is a chicken. (premise)
– Therefore Clucko is a feathered animal. (guaranteed
conclusion)
Formal Fallacies
– All chickens are feathered animals. (premise)
– Quacko is a feathered animal. (premise)
– Therefore Quacko is a chicken. (non-guaranteed
conclusion)

This argument commits a formal fallacy in that
its form doesn’t guarantee the truth of its
conclusion, even if the initial premises are true.
The Problem of Conclusiveness in an Argument
Real-world arguments address contestable
issues of truth and value that cannot be resolved
with mathematical certainty.
 Disputants can create only more or less
persuasive arguments, never conclusive ones.

The Problem of Conclusiveness in an Argument
Real-world
Arguments
Unpersuasive
Persuasive
Conclusive
•Logically sound
•Air-tight argument
Informal Fallacies

They are flaws in the structure of an argument.

They sometimes make flawed reasoning seem
deceptively persuasive.
Why Study Informal Fallacies?

Knowledge of informal fallacies is most useful when we
run across arguments that we “know” are wrong, but we
cannot quite say why.

Knowledge of informal fallacies can help you locate
specific weaknesses in others’ arguments . . . and in
your own!
Informal Fallacies: Three Categories
1. Fallacies of Pathos
2. Fallacies of Ethos
3. Fallacies of Logos
Fallacies of Pathos

Rest on flaws in the way an argument appeals to
the audience’s emotions and values
–
–
–
–
–
Argument to the People
Appeal to Ignorance
Appeal to Popularity
Appeal to Pity
Red Herring
Argument to the People
Appeal to Stirring Symbols

Appeal to the fundamental beliefs, biases, and
prejudices of the audience in order to sway
opinion through a feeling of solidarity among
those of a group.
Argument to the People
Appeal to Stirring Symbols

The stirring symbol of the American flag
– Allegiance to nationalistic values
– Solidarity of American citizens

Ex: Joe Politician delivering a speech while wearing a
suit made out material patterned with the American flag.

Ex: Marilyn Manson wiping his butt on an American flag.
Appeal to Ignorance

Presenting assumptions, assertions, or evidence
that the audience is incapable of examining or
judging.

In other words, maintaining that because a
claim has not been disproved, it must be true.
Appeal to Ignorance

Ex: Researchers have not conclusively shown that there
is no monster at the bottom of Loch Ness; therefore, we
should expect to see the monster at any time.

Ex: There must be intelligent life on other planets. No
one has proven that there isn’t.
Appeal to Ignorance

Ex: Genetically modified organisms must be dangerous
to our health because science has not proved that they
are safe.

Ex: Jones must have used steroids to get those bulging
muscles because he cannot prove that he has not used
steroids.
Appeal to Popularity
The Bandwagon Appeal



The argument rests on the assertion that since
everybody else is doing something, you should do it too.
These appeals are fallacious because the popularity of
something is irrelevant to its actual merits.
These appeals are common in advertising where the
claim that a product is popular substitutes for evidence
of the product’s excellence.
Appeal to Popularity
The Bandwagon Appeal

Ex: All the popular, cool kids have tattoos; therefore, I
should get a tattoo.

Ex: Everybody who has a Facebook page has a lot of
friends; therefore, I should make a Facebook page.
Appeal to Popularity
The Bandwagon Appeal

Ex: Living together before marriage is the right
thing to do because most couples are now doing
it.

Ex: You should buy a Toyota Camry because it
is the best-selling car in the world.
Appeal to Pity

The arguer appeals to the audience’s
sympathetic feelings in order to support a claim
that should be decided on more relevant or
objective grounds.
Appeal to Pity

Ex: “Professor Rose, I’m sorry I couldn’t finish my
essay. You don’t understand how difficult my life is right
now. My parents could not afford to send me to college,
and I have to work two part-time jobs to pay for my
classes and books.”
Appeal to Pity

Ex: “Honorable Judge, I should not be fined $250 for
driving 85 mph in a 25 mph zone because I was
distraught from hearing the news of my brother’s illness
and was rushing to see him in the hospital.”
Red Herring

Refers to the practice of throwing an audience
off track by raising an unrelated or irrelevant
point.

The name derives from the practice of using a red
herring (a very smelly fish) to throw dogs off from a
scent that they are supposed to be tracking.
Red Herring

Ex: Jack’s girlfriend asks, “Where were you last night?”
Jack answers, “I sure am glad to see you. You look
extra beautiful today!”

Ex: Question to politician, “What’s your stand on gun
control?” Politician’s reply, “I’m for family values.”
Red Herring

Ex: I don’t believe we should elect this
candidate because she would have to put her
children in daycare.
Fallacies of Ethos

Fallacies of Ethos = Rest on a flawed
relationship between the argument and the
character of those involved in the argument.

Often these fallacies attack character or use
character instead of evidence for proof.
Appeal to False Authority

The arguer appeals to the authority of a popular person
rather than a knowledgeable one.

Many advertisements are based on this fallacy.

Testimony to support an argument should come from a
person competent in the field.
Appeal to False Authority

Kobe Bryant says that Wheaties cereal keeps him on his
game; therefore, Wheaties cereal is a good cereal.

Real evidence about the quality of Wheaties cereal
would include specific information about its nutritional
content rather than testimony from a hired athlete.
Appeal to False Authority

Tom Cruise says that postpartum depression can be best
treated with vitamins because anti-depressant drugs are
dangerous. Therefore, all women who claim they have
postpartum depression should stop taking antidepressants and start taking vitamins.
Ad Hominem
Appeal to the person

Arguments that attack the character of the
arguer rather than the argument itself
– Name-calling (referring to a disputant by unsavory
names)
– Appeal to prejudice (applying ethnic, racial, gender,
or religious slurs to an opponent)
– Guilt by association (linking the opposition to
extremely unpopular groups or causes)
– Poisoning the Well (discrediting an opponent or an
opposing view in advance)
Ad Hominem
Appeal to the person

In politics, Ad Hominem can be found on the first page--nay, the
first few words--of every politician's playbook. Why debate the pros
and cons of universal health care when you can just call your
opponent a socialist and get a cheer from the conservatives in the
audience?

There are lots of words that get thrown around in political ad
hominem arguments, leading to the common charge of "namecalling" and "mud-slinging": racist, nazi, hippy, teabagger, antichrist, etc.
Ad Hominem
Appeal to the person

Name-calling
– Ex: OJ Simpson claims that he is innocent, but he’s a
wife beater.
– Ex: Hugh Hefner, founder of Playboy magazine, has
argued against the censorship of pornography. But
Hefner is an immature, self-indulgent millionaire who
never outgrew the adolescent fantasies of his youth.
His argument is worthless.
Ad Hominem
Appeal to the person

Appeal to prejudice
– Ex: Because he is extremely wealthy, our mayor
cannot properly represent this city.
– Ex: Of course she is in favor of Affirmative Action.
What do you expect from a black woman?
Ad Hominem
Appeal to the person

Guilt by Association
– Ex: Of course you support medical marijuana. All of
your friends are a bunch of pot-head hippies.
– Ex: Professor Smith has argued against the theory of
evolution. But he’s a member of the Communist
Bikers’ Association. I refuse to listen to him!
Ad Hominem
Appeal to the person

Poisoning the Well

Ex: You are told, prior to meeting him, that your friend’s
boyfriend is a poseur and a mooch. When you meet
him, everything you hear him say is tainted.

Ex: Before I leave the floor to the next speaker, I must
remind you that persons who oppose my plan do not
have the best interests of the working people in their
hearts.
Straw Man
Greatly oversimplifying an opponent’s argument
in order to make it easier to refute or ridicule
 Diverts attention from the real issue


The name comes from the practice of stuffing dummies and
scarecrows with straw. When one attacks an opponent by putting
words into the opponent’s mouth, one makes up a “dummy”
position. But just as beating up a scarecrow doesn’t demonstrate
any athletic accomplishment, beating up a “straw man” in an
argument doesn’t demonstrate anything.
Straw Man

Ex: You many think that levying confiscatory taxes on
homeless people’s cardboard dwellings is the surest way
out of a recession, but I don’t.

Ex: While my opponent would like to empty our prisons
of serial killers, I hold to the sacred principles of
compensatory justice.
Fallacies of Logos

Rest on flaws in the relationship among
statements in an argument
Hasty Generalization

Making a broad generalization on the basis of
too little evidence

Ex: Yesterday I met the most remarkable
person. He is kind, considerate, sensitive, and
thoughtful.
Hasty Generalization

Ex: Jean writes poetry, and she’s very sensitive and
frequently depressed. People who write poetry are
sensitive and prone to depression.
Post Hoc, Ergo Propter Hoc
After This, Therefore Because of This
Occurs when a sequential relationship is
mistaken for a causal relationship
 Confusing correlation for cause
 Ex: Event A occurred before Event B; therefore,
Event A must have caused Event B.

Post Hoc, Ergo Propter Hoc
After This, Therefore Because of This

Ex: Governor X took office in 2008. In 2009,
the state suffered a severe recession.
Therefore, Governor X should not be re-elected.
Post Hoc, Ergo Propter Hoc
After This, Therefore Because of This

Superstition is often based on this fallacy.

Ex: Since I walked under that ladder yesterday, I’ve lost
my wallet and received a speeding ticket.

Ex: Everything was going fine until the lunar eclipse last
month; that’s why the economy is in trouble.
Begging the Question
Circular Reasoning

Supporting a claim with a reason that
simply restates the claim in different
words
– Ex: Bungee-jumping is dangerous because it’s
unsafe.
– Ex: Women should not be permitted to join men’s
clubs because the clubs are for men only.
Begging the Question
Circular Reasoning

Ex: Abortion is murder because it is the
intentional taking of the life of a human being.
False Dilemma – Either/Or



Oversimplifying a complex issue so that only two choices
appear possible
No alternative, middle-ground, or compromise positions
are acknowledged.
Often one of the choices is made to seem unacceptable ,
so the only remaining option is the other choice.
– Ex: It’s my way or the highway.
False Dilemma – Either/Or

Ex: Love football or you’re not a man.

Ex: A woman can either be a mother or have a
career.

Ex: Either we get tough with drug users, or we
legalize all drugs.
False Dilemma – Either/Or
Slippery Slope
Based on the fear that once we put a foot on a
slippery slope heading in the wrong direction,
we will have to keep going.
 Often functions as a scare tactic

Slippery Slope

Ex: Look, Joe, no one feels worse about your
need for open-heart surgery than I do. But I
still cannot let you turn this essay in late. If I
were to let you do it, then I would have to let
everyone turn essays in late.
Slippery Slope

Ex: We don’t dare legalize marijuana. If we do,
we’ll have to legalize cocaine, then ecstasy, and
then heroin. Finally, all hard hard drugs will be
available anywhere to anybody.
False Analogy

Arguments by analogy use a comparison as
though it were evidence to support a claim.

An argument by analogy is only as strong as the
comparison on which it rests. The false analogy
fallacy is committed when the comparison is not
strong enough.
False Analogy

Ex: There is no convincing evidence to show
that cigarette smoking is harmful. Too much of
anything is harmful. Too much Jell-O is harmful.
False Analogy

Ex: Mountain climber talking to his
mother, “I don’t want to die falling off a
rock. But you can kill yourself falling in
the bathtub, too.”
False Analogy

Ex: In his autobiography, Tommy Chong writes
that when DEA (Drug Enforcement
Administration) agents raided his house he saw
himself as “Anne Frank talking to Herr Mengele.
. . For the first time, I felt like I could
understand what the Jews suffered under Hitler,
and this was happening in America in 2003.”
False Analogy
Non Sequitur
It Does Not Follow
Making a claim that does not follow logically
from the premises or is supported by irrelevant
premises.
 The arguer seems to make an inexplicably
illogical leap.

Non Sequitur
It Does Not Follow

Ex: Violent video games have some social
value because the Army uses them for
recruiting.

There may be an important idea emerging here,
but too many logical steps are missing.
Non Sequitur
It Does Not Follow

Ex: Our university has one of the best faculties
in the U.S. because a Nobel Prize winner used to
teach here.

How does the fact that a Nobel Prize winner used to
teach at our university make its present faculty one of
the best in the U.S.?
Non Sequitur
It Does Not Follow

Ex: It’s a beautiful day! We don’t need to be in
class.

Ex: The professor in the Hawaiian shirt and flip
flops must be an easy grader.
Non Sequitur
It Does Not Follow

Ex: Donald Trump, the billionaire real-estate developer,
in considering a run for president in 2000, told an
interviewer:
–

“My entire life, I’ve watched politicians bragging about how poor they are, how
they came from nothing, how poor their parents and grandparents were. And I
said to myself, if they can stay so poor for so many generations, maybe this isn’t
the kind of person we want to be electing to a higher office. How smart can
they be? They’re morons. Do you want someone who gets to be president and
that’s literally the highest paying job he’s ever had?”
As a brief glance at U.S history shows, it does not follow
that men of small success in the world of commerce are
unfit to make sound decisions about matters of state.