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LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC
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LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Jan 11, 2016

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Page 1: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

LOGICAL FALLACIES

Common Mistakes in Weak Arguments

DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC

Page 2: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Introduction

Ad Hominem Hasty Generalization Oversimplification Begging the Question or Circular Logic Post Hoc Red Herring or Ignoring the question Non Sequitur Either-or Slippery-slope False Analogy Appeal to Ignorance Appeal to Pity Bandwagon Slanted Language Testimonial

Page 3: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Definition

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.

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Most logical fallacies masquerade as reasonable statements, but they are in fact attempts to manipulate readers by reaching their emotions instead of their intellects.

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Ad Hominem

Latin for to the manDirectly attacks someone’s appearance, personal habits, or character rather than focusing on the merit of the issue at hand. The implication is that if something is wrong with this person, whatever he/she says must be wrong.

How can you say he’s a good musician when he’s been in and out of rehab for three years?

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Ad Hominem – Making it Personal

Sara is divorced, so whatever relationship advice she gives you can’t be good.

It is the suggestions, not the person who makes them that deserve attention. Sara’s marital status has nothing to do with the quality of her advice. Isn’t it also possible that Sara could be married and give awful advice?

If my husband forgot to wash his dish, I would move out too. You did the right thing, Carol.

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Hasty Generalization

A hasty generalization is a conclusion based on insufficient or unrepresentative evidence.

Stereotyping and Sexism are forms of this fallacy.

Take, for example common dumb blonde jokes:

Q: What do you call a blonde’s skeleton in the closet?

A: Last year's hide-and-go-seek winner.

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Example of a Generalization

The only redheads I know are rude.

Therefore, all redheads must have bad

manners.

If the speaker only knows two redheads, then he has insufficient evidence to make the general claim about all people with that hair color.

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Either – Or / False Dilemma

A false dilemma asserts that a complex situation can have only two possible outcomes and that one of the options is necessary or preferable.

Either go to college or forget about making money.

This falsely implies that a college education is a pre-requisite for financial success.

Was it her college education that made Britney tons of money?

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Begging the Question/ Circular Logic

This is a kind of circular argument where the support only restates the claim.

Wrestling is dangerous because it is unsafe.

Jogging is fun because it is enjoyable.

Unsafe means the same thing as dangerous and fun means the same thing as enjoyable. This makes the reasoning circular.

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Post Hoc Fallacy

Short for post hoc, ergo propter hoc, which means after this, therefore caused by this.

This fallacy assumes that just because Bhappened after A, it must have been causedby A.

Politicians love this one.

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Post Hoc Example

Since Governor Bush took office, unemployment of minorities in the state has decreased by seven percent. Governor Bush should be applauded for reducing unemployment among minorities.

Before we pat the governor on the back, the speaker

must show that Bush’s policies are responsible for the decrease in unemployment. It is not enough to show the decrease came after his election.

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Oversimplification (& Exaggeration)

Causation fallacies known as oversimplification & exaggeration occur whenever the series of actual causes for an event are either reduced or multiplied to the point where there is no longer a genuine, causal connection between the alleged causes and the actual effect. In other words, multiple causes are reduced to just one or a few (oversimplification) or a couple of causes are multiplied into many (exaggeration).

Signal of oversimplification:The arguer makes a complex problem sound simple.

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Oversimplification example

School violence has gone up and academic performance has gone down ever since organized prayer was banned at public schools. Therefore, prayer should be reintroduced, resulting in school improvement.

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Ignoring the Question/Red Herring

Partway through an argument, the arguer goes off on a tangent, raising a side issue that distracts the audience from what's really at stake. Often, the arguer never returns to the original issue.

Etymology:From the practice of distracting hunting dogs by dragging a smelly, salt-cured herring across the trail of the animal they were pursuing.

Page 16: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Red Herring example

"Grading this exam on a curve would be the most fair thing to do. After all, classes go more smoothly when the students and the professor are getting along well." What's wrong with this argument?

Premise: Classes go more smoothly when the students and the professor are getting along well.

Conclusion: Grading this exam on a curve would be the most fair thing to do.

It's pretty obvious that the arguer went off on a tangent—the fact that something helps people get along doesn't necessarily make it more fair; fairness and justice sometimes require us to do things that cause conflict. But the audience may feel like the issue of teachers and students agreeing is important and be distracted from the fact that the arguer has not given any evidence as to why a curve would be fair.

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Non Sequitur

Definition: a conclusion does not follow logically from what preceded it. "A non sequitur is any pretended jump in logic that doesn't work cleanly, perhaps because of unfounded premises, unmentioned complicating factors, or alternative explanations.

Page 18: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Non Sequitur example

'This war is righteous because we are French!'

'You will do what I say because you are my husband!'"

Page 19: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Slippery Slope

The arguer claims that a sort of chain reaction, usually ending in some dire consequence, will take place, but there's really not enough evidence for that assumption. The arguer asserts that if we take even one step onto the "slippery slope," we will end up sliding all the way to the bottom; he or she assumes we can't stop halfway down the hill.

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Slippery Slope example

Here's an example that doesn't seem fallacious:

"If I fail English 101, I won't be able to graduate. If I don't graduate, I probably won't be able to get a good job, and I may very well end up doing temp work or flipping burgers for the next year."

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False Analogy

An analogy points out similarities in things that are otherwise different. A false analogy claims comparison when differences outweigh similarities. Essentially, it’s comparing apples and oranges!

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False Analogy Example

If we can put a man on the moon, why

can’t we find the cure for the common

cold?

While both things being compared here are related to science, there are more differences than similarities between space and biological advancements.

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Appeal to Ignorance

Appealing to a lack of information to prove a point, or arguing that, since the opposition cannot disprove a claim, the opposite stance must be true. An example of such an argument is the assertion that ghosts must exist because no one has been able to prove that they do not exist. Logicians know this is a logical fallacy because no competing argument has yet revealed itself.

example: “I know that God doesn't exist because nobody has yet been able to prove God's existence.”

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Appeal to Pity

An emotional appeal concerning what should be a logical issue during a debate. While pathos generally works to reinforce a reader’s sense of duty or outrage at some abuse, if a writer tries to use emotion merely for the sake of getting the reader to accept what should be a logical conclusion, the argument is a fallacy.

For example, in the 1880s, prosecutors in a Virginia court presented overwhelming proof that a boy was guilty of murdering his parents with an ax. The defense presented a "not-guilty" plea on the grounds that the boy was now an orphan, with no one to look after his interests if the court was not lenient. This appeal to emotion obviously seems misplaced, and the argument is irrelevant to the question of whether or not he did the crime.

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Bandwagon

“Everybody is doing it.” This argumentum ad populum asserts that, since the majority of people believes an argument or chooses a particular course of action, the argument must be true, or the course of action must be followed, or the decision must be the best choice.

"Since Harvard, Stanford, and Berkeley have all added a multicultural component to their graduations requirements, Notre Dame should get with the future."

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Slanted Language

Occurs when slanted language is used to reaffirm what we wish to prove but have not proven yet.

No right-thinking American could support this measure, a cunning plot hatched in back rooms by corrupt politicians.

No right-thinking American could support this measure, a cunning plot hatched in back rooms by corrupt politicians.

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Testimonial

An appeal to an improper authority, such as a famous person or a source that may not be reliable. This fallacy attempts to capitalize upon feelings of respect or familiarity with a famous individual. It is not fallacious to refer to an admitted authority if the individual’s expertise is within a strict field of knowledge

"I'm not a doctor but I play one on T.V. Use this aspirin."

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Testimonial - 2

A subcategory is the Appeal to Biased Authority. In this sort of appeal, the authority is one who actually is knowledgeable on the matter, but one who may have professional or personal motivations that render his professional judgment suspect: – "To determine whether fraternities are beneficial to this campus,

we interviewed all the frat presidents." – "To find out whether or not sludge-mining really is endangering

the Tuskogee salamander's breeding grounds, we interviewed the supervisors of the sludge-mines, who declared there is no problem."

Indeed, it is important to get "both viewpoints" on an argument, but basing a substantial part of your argument on a source that has personal, professional, or financial interests at stake may lead to biased arguments.

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Identify Logical Fallacies

“ ‘Either they voted for the candidate or they voted for the candidate’s opponent’ ” (Corbett and Connors 67).

“Any man who is honest will not steal. My client is honest. Therefore, my client would not steal” (Corbett and Connors 69).

Page 30: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Answers

“ ‘Either they voted for the candidate or theyvoted for the candidate’s opponent’ ” (Corbett

and Connors 67).

EITHER/OR FALLACY

“Any man who is honest will not steal. My client is honest. Therefore, my client would not steal” (Corbett and Connors 69).

BEGGING THE QUESTION

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Identify Logical Fallacies

“ ‘My opponent’s arguments are very

impressive, but remember, this is the

man who deserted his faithful wife

and family after he had won his firstpolitical victory.’ ” (Corbett and

Connors 70).

Page 32: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Answer

“ ‘My opponent’s arguments are very

impressive, but remember, this is the man

who deserted his faithful wife and family

after he had won his first political victory’ ”(Corbett and Connors 70).

AD HOMINEM

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Identify Logical Fallacies

“ ‘You accuse me of cheating on my

income tax, but doesn’t everybodycheat a little bit’ ” (Corbett and

Connors 70)?

“ ‘Why did you steal the diamondring’ ” (Corbett and Connors 71)?

Page 34: LOGICAL FALLACIES Common Mistakes in Weak Arguments DEVELOPED BY JENIFFER VISCARRA & adapted by Sharon Ma, SMIC.

Answer

“ ‘You accuse me of cheating on my income tax, but doesn’t everybody cheat a little bit’ ” (Corbett and Connors 70)?

RED HERRINGOR FAULTY GENERALIZATION

“ ‘Why did you steal the diamondring’ ” (Corbett and Connors 71)?

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Summary

A logical fallacy is simply poor logic.The presence of logical fallacies may

weaken a writing project.It’s often useful to point out logical

fallacies as weak points in your opponent’s argument.

Logical fallacies are usually forms of inaccurate assumptions, bias, jumps in thought, & overgeneralizations.

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Sources Used

Troyka, Lynn Quitman. Quick Access. New Jersey: Prentice Hall, 2001.Logical Fallacies by Dr. Karen Lee,

M.F.A., Ph.D. The Writing Center @ Vanguard University of Southern California

Hackard, Dianne. Rules for WritersThe Compact Reader, Chapter 13