Oxford University Press In This Chapter Fallacies of Relevance Fallacies of Unwarranted Assumption Fallacies of Ambiguity or Diversion Recognizing Fallacies in Ordinary Language Oxford University Press ID: 513903
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Chapter 4: Informal Fallacies
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In This ChapterFallacies of Relevance Fallacies of Unwarranted Assumption
Fallacies of Ambiguity or Diversion
Recognizing Fallacies in Ordinary Language
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Fallacies of Unwarranted Assumption
Arguments that assume the truth of some unproved or questionable claim.
Begging the Question
Complex Question
Biased Sample
Accident
Hasty Generalization
Misleading Precision
False DichotomyFalse DilemmaFalse Cause Fallacies: Coincidence Post Hoc Fallacy Common Cause Fallacy Slippery Slope
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Begging the QuestionPetitio Principii — “assumption at the beginning”
Assumes as evidence in the premises the very thing that it attempts to prove in the conclusion.
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Jane has the highest GPA among all the seniors in my school.
There are three hundred graduating seniors in my class. Therefore,
no senior has a higher GPA than her.
Premise and the conclusion say the same thing; premise becomes irrelevant. See also “circular reasoning”Slide5
The first and most common example is to leave out a possibly false premise:Murder is morally wrong. This being the case, abortion is morally wrong.
Of course humans and apes evolved from common ancestors. Just look at how similar they are.
Clearly, terminally ill patients have a right to doctor-assisted suicide. After all, many of these people are unable to commit suicide by themselves.
The world in which we live displays an amazing degree of organization. Obviously this world was created by an intelligent God.
What are the missing premises?
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Second form: the argument restates a possibly false premise in slightly different language.Capital punishment is justified for the crimes of murder and kidnapping because it is quite legitimate and appropriate that someone be put to death for having committed such hateful and inhuman acts.
Anyone who preaches revolution has a vision of the future for the simple reason that if a person has no vision of the future he could not possibly preach revolution.
Third form: circular reasoning
Ford Motor Company clearly produces the finest cars in the US. We know they produce the finest cars because they have the best design engineers. This is true because they can afford to pay them more than other manufacturers. Obviously they can afford to pay them more because they produce the finest cars in the United States.
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Consider:No dogs are cats.Therefore, no cats are dogs.
London is in England and Paris is in France.Therefore, Paris is in France and London is in England.
These arguments are sound: they are valid and have true premises. No fallacy is committed because there is no illusion created to make inadequate premises appear as adequate. Thus, this argument:
My brother suffers from insomnia. Therefore, my brother has difficulty sleeping.
commits no fallacy. Notice that arguments that beg the question are normally valid.
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Complex Question A single question that actually contains multiple, hidden parts.
Do you still cheat on your taxes
?
Answering “yes” or “no” presumes you do or did cheat on your taxes.
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I asked you if you still cheated on your taxes. You said "No." Therefore, by your own admission you did cheat on your taxes.
The premises rely on two distinct questions:
Did you ever cheat on your taxes?
Do you now cheat on your taxes?
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Biased SampleUses a nonrepresentative sample as support for a statistical claim about an entire population.
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Evidence shows that approximately
85%
of all Americans believe that abortion is morally wrong. Recently, a sample of Catholics revealed that
85%
believe that abortion is morally wrong.
The sample surveyed only Catholics, but the conclusion generalizes to all Americans.
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AccidentRigid Application of a
Generalization
When a generalization is inappropriately applied to the case at hand
.
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I can’t believe that the police didn’t give the driver of that ambulance any citations. The driver was speeding. The driver went through a red light. The ambulance swerved from lane to lane without using any turn signals.
While nonemergency vehicles are subject to penalties, exceptions apply to ambulances when responding to emergencies.
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Examples:Freedom of speech is a constitutionally guaranteed right. Therefore, John Q. Radical should not be arrested for his speech that incited the riot last night.
Property should be returned to its rightful owner. That drunken sailor who is starting a fight with his opponents at the pool table lent you his .45-caliber pistol, and now he wants it back. Therefore, you should return it to him now.
The First Amendment to the Constitution prevents the government from interfering with the free exercise of religion. The liturgical practice of the Religion of the
Internal Enlightenment involves human sacrifice. Therefore, it would be wrong for the government to interfere with this religious practice.
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Hasty Generalization
Converse Accident
A generalization created on the basis of a few instances
.
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I saw a fraternity guy act rudely to a fast food employee in the food court at lunch today. Probably most fraternity and sorority members are rude and arrogant.
The premise reports a single instance, while the conclusion generalizes the behavior to most fraternity and sorority members.
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Examples:After only one year the alternator when out in Mr. O’Grady’s new Chevrolet. Mrs. Dodson’s Buick developed a transmission problem after six months. The obvious conclusion is that cars made by General Motors are just a pile of junk these days.
Ten Arab fundamentalists hijacked planes and crashed them into the World Trade Center in New York City. The message is clear: Arabs are nothing but a pack of religious fanatics prone to violence.
Note: a small sample does not necessarily mean that it’s atypical:
Ten milligrams of substance Z was fed to four mice, and within two minutes, all four went into shock and died. Probably, substance Z is fatal to mice.
On three separate occasions, I drank a bottle of
Figowitz
beer and found it flat and bitter. I would probably find every bottle of
Figowitz
flat and bitter. © Oxford University PressSlide14
Misleading PrecisionA claim that appears to be statistically significant, but is not.
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Our cookies contain
30
% less fat, so you should start eating them if you want to lose weight.
It is fair to ask,
“30
% less fat than what?” We need to know before we can judge the significance of this claim. Slide15
False Dichotomy
A fallacy that occurs when it is assumed that only two choices are possible
, when in fact others exist
.
Either you agree with me or you are an idiot
.
Two reconstructions ignore additional choices:
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Either you agree with me or you are an idiot.You do not agree with me. You are an idiot.Either you agree with me or you are an idiot.You are not an idiot.You agree with me.
Either you agree with me or you are an idiot or
your position is correct
.
You do not agree with me.
You are not an idiot.
Your position is correct.Slide16
Examples:Either you let me attend the Miley Cyrus concert or I’ll be miserable for the rest of my life. You don’t want
me to be miserable, so you gotta let me go to that concert!
Either you use Ultra Guard deodorant or you risk the chance of perspiration odor. You don’t want to stink. Therefore, you must use Ultra Guard.
If the alternatives are exhaustive, then no fallacy is committed:
Either Reno is in Nevada or it is not in Nevada.
Or if one of the alternatives of the disjunction is true:
Either Seattle is in Washington, or it is in Oregon.
Seattle is not in Oregon.
Therefore, Seattle is in Washington. © Oxford University PressSlide17
False Dilemma
dilemma
–
“double proposition”
Occurs
when two choices are asserted,
each leading to an
unwanted result, with failure to acknowledge that other possibilities exist.Either we give up some traditional basic freedoms, or we lose the war on terror.© Oxford University PressG = we give up some traditional basic freedoms G or LL = we lose the war on terror Not L
G
What are other possible choices? Can we win the war on terror without giving up some traditional basic freedoms?Slide18
False Cause FallaciesOccur when a causal connection is assumed to exist between two events when none actually exists.
Coincidence
Post Hoc
Fallacy
Common Cause Fallacy
Slippery Slope
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Coincidence© Oxford University Press
Results from the accidental or chance connection between two events.
I can prove that some dreams let us see into the future. Last week, I dreamed that my cousin Charlie was in a terrible car wreck.
Just now, I got a phone call from my cousin Charlie's wife saying that he is in the hospital because he was in a car accident.
We have thousands of dreams a year; a few are likely to resemble real events. We forget that most dreams do not connect to real events.
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Post Hoc Fallacy© Oxford University Press
post hoc, ergo propter hoc
–
“after the fact, therefore because of the fact.”
Involves a short-term pattern noticed after the fact.
Researchers have found a pattern showing that
while a Democrat was president, Morphiacola topped all soft-drink sales.
While a Republican was president, Opiacola topped all sales. You should invest in the soft-drink company based on who is in the White House.This post hoc argument falls prey to the mistake of confusing a correlation with a cause.
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Examples of post hoc:
During the past two months, every time the cheerleaders have worn blue ribbons in their hair, the basketball team has been defeated. Therefore, to prevent defeats in the future, the cheerleaders should get rid of those blue ribbons.
A few minutes after President Obama finished his speech on television, a devastating earthquake hit California. For the safety of the people out there, it is imperative the President Obama make no more speeches.
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Common Cause Fallacy© Oxford University Press
Occurs when one event is assumed to cause another when both events are the result of a common cause.
A falling barometer is the cause of a storm.
In fact, both events are caused by a change in atmospheric pressure. Slide23
Slippery SlopeAttempts to make a final event the inevitable outcome of an initial
act.
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If you start smoking marijuana for pleasure, you will need more and more to achieve the expected high.
You will begin to rely on it whenever you feel depressed.
Eventually you will experiment with more powerful drugs. The amount of drug intake will have to increase to achieve the desired results.
At this point, the addiction will take hold and will lead to a loss of ambition, a loss of self-esteem, the destruction of your health, and the dissolution of all social ties. Therefore, you should not start smoking marijuana.Relies on a causal network with each step in the chain causing next step. The alleged inevitability of the final act needs is not supported by objective evidence.
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Slippery slopes can cut both directions:Immediate steps should be taken to outlaw pornography once and for all. The continued manufacture and sale of pornographic material will almost certainly lead to an increase in sex crimes such as rape and incest. This in turn will gradually erode the moral fabric of society and result in an increase of crimes of all sorts. Eventually a complete disintegration of law and order will occur, leading in the end to the total collapse of civilization.
And:
Attempts to outlaw pornography threaten basic civil liberties and should be summarily abandoned. If pornography is outlawed, censorship of newspapers and news sources is only a short step away. After that there will be censorship of textbooks, political speeches, and the content of lectures by university professors. Complete mind control by the central government is the inevitable result.
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Check Your Understanding 4BExample I
A single question that actually contains multiple, hidden parts is an example of Begging the Question.
Answer
False
Example II
Every time
Mychal
heard that song on the radio he sold more memberships to the club than usual and increased his commission! I think he should listen to that song each day before work.
Answer Post Hoc fallacy© Oxford University Press