Transcript Informal Fallacies

Informal Fallacies
Chapter 5
Formal vs. Informal fallacy

Formal
– The logic is wrong– Not sound
– Bad reason fallacy: error in the way the argument is
structured or built (invalid set up, 9 rules)
– Doesn't force a true conclusion with all true premise

Informal
– Mask Man fallacy: subjective, emotional language in
propositions.
The masked man is Mr. Hyde. T
The witness believes the masked man committed the crime. T
Therefore, Mr. Hyde committed the crime. F
Informal Fallacy

Error with the content of arguments
– Words chosen
– Phrases chosen
How we express our arguments
 Can be formally valid, built logically
 Allows you to notice irrational thought
Informal fallacies are defects found in the
content of the argument, which could be
inductive or deductive.

Major types of informal fallacies

Fallacies of ambiguity (Cleaner)
– The words or phrases need to be defined- or are
vague- or change meaning in the argument

Fallacies of relevance (Connection)
– The considerations that are offered in support of the
conclusion are irrelevant to determining whether that
conclusion is true. It makes it possible for the
premises to all be true and conclusion to be false.

Fallacies of assumption (Conjecture)
– Have false (or at least unwarranted) assumptions,
which fails to establish inference to the conclusion
(must be true). Assume one premise to be true
Fallacies of ambiguity
Word choices makes a confusing premise
Equivocation

Words often have more than one meaning
– Different definition of word or phrase
– Use subjective or relative words or phrases
 Tall/Short
 Hot/Cold
 What are rights?
 What’s a good salary?
 What’s a good mate?
 “I’m to see the Doctor…………………”
Amphiboly
Grammatical error leads to confusion.
 Bad or unclear writing/speaking

– A man shot himself after making a fond
farewell to his family with a shotgun
 Is it the man shot himself with a shot gun or that
he gave his family a fond farewell with a shotgun
– Ad for an apartment: 3 rooms, river view,
private phone, bath, kitchen, utilities included
 Is it just a private phone or private phone, bath
and kitchen?
Accent

Different emphasis on certain words
changes meaning or context
– THESE (!) are your friends
– These are YOUR (!) friends
You misinterpret the meaning because of and
accent on a word or phrase

Can be cultural or regional
– Automobile story
Composition

The whole is like the individual
– Buses use more gas then cars
– True one bus to one car BUT NOT ALL buses
to ALL cars (more cars)

Can be fixed by clarifying wording
Most buses uses more gas than automobiles,
but there are more automobiles. Thus, as a
whole- automobiles use more gas
Division

The pieces are like the whole
– This hotel must have nice suites because the
outside and lobby is so nice.
– The whole car is of quality means every part
in the car is of quality
– ALL men are DOGS. Mr. V is a man, therefore
Mr. V is a DOG!
Name that Fallacy
Fallacies of relevance
Premises are unrelated to conclusion
Emotion

Rely on the feelings of the audience to
influence one’s argument
– Patriotic speeches
– Ads on TV
– Appeal to pity
– I was late for work that
(Hitler)
(Shoes-- Athlete)
(Court Cases)
is why I was speeding
Red Herring- distraction
Distract the other person from real
argument or too ambiguous of a
connection.
 Loose(n) focus.

– Gambling is good because taxes are too high
– We need to be in Iraq, only 800 Iraqi soldiers (T/F?)
– Duke (2006): Three students accused of rape,
one professor defended the prosecutor’s
indictment by saying that the real bad thing is
that 18% of the population was below the
poverty line.
Straw Man

Change opponents argument. Putting
words in opponents mouth to make it
easier to refute or beat
– When you talk about universal health care
you are talking about Socialism.
– When you are talking about same sex
marriage you are saying we need to destroy
the family dynamics in the US.
Against the person
Latin: ad hominem
You don’t attack argument you attack the
person who is arguing with you
 Abusive: Direct attack on the person

– If against affirmed action, then you are a racist
– If you are a liberal, then you are part of the “Loony
Left”

Circumstantial: Attack a person’s status/group.
Also called Poisoning the well
– If you go to that school, then you are not smart
– If those are your friends then you are bad too
Appeal to force

To force someone to accept a claim with a
physical or physiological confrontation
– Physical force
– Lawsuits to scare
– Symbols to influence
 Nazi
 American Flag
 Police shield
From Ignorance
Assume true because not proven false
OR
 Assume false because not proven true
 You have to make your own argument

– You can’t prove UFOs are false so they must
be true
– You can’t prove I’m guilty so I must be
Innocent.
Name that Fallacy
Fallacies of Assumptions
Assume premise to be true without proof
Begging the question

The conclusion is just a rewording of one
of the premises. Also called circular logic
– Freedom of speech is good because everyone
is free to say what they want.
– Capital punishment is wrong because you are
putting someone to death is wrong.
– God exists because the bible says so (which is
the word of God)
Inappropriate Authority

Use testimony of expert (credibility) in an
area that they are not an expert in.
– Politics
 The president thinks genetic engineer is
wrong/right
 Is he/she a scientists?
– Ads
 Tiger Woods Drives this car
 Does he race or engineer cars?
Loaded

(Complex)
Question
Suppose the truth of another question in a
premise to justify the conclusion
– How did you feel when you took all that
money from the bank?
 Assumes you did take it and the question asks
about your emotions
– You support the right to bear arms and the
Republican Party.
 Assumes you support both causes
False Dilemma

Forces the argument into two choices
when there are many. Limits your options.
– Very popular in Politics, sports and
relationships
 Either you are with us or against us
 Either you like the team or hate the team
 Either you love me or you don’t
False Cause

The casual relationship in a premise is not
a true relationship.
– Less religion in school causes gangs
– Death penalty decreases crime
Could be plenty of other factors that cause
gangs and decreases crime. Could be one
factor, but maybe not the most important one
Name that Fallacy
Strategies for avoiding fallacies
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Know yourself
–Knowing which fallacies you use
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Build your self-confidence and self-esteem
–Notice and address fallacies in others, make
good argument yourself


Cultivate good listening skills
Avoid ambiguous and vague terms and
faulty grammar
–Clearly define your key terms.
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Adopt a position of skepticism
–Don’t just take people’s word for it. Also remain
skeptical about your own position.