Logical Fallacies
by Dr. Karen Lee, M.F.A., Ph.D.
The Writing Center
@ Vanguard University
of Southern California
“Faith and knowledge resting on the
hope of eternal life . . .” (NIV, Titus 1.2).
Version Date: 3.10.06, [email protected], Colossians 2.8
Grateful Acknowledgments
• Exercises are briefly excerpted from Classical
Rhetoric for the Modern Student by Corbett, Edward
P.J. and Robert J. Connors. New York: Oxford
University Press, 1999. (This textbook is used in
our upper-division English course, ENG 370:
Advanced Rhetoric & Composition.)
• Short passages by H.L. Mencken and Herman
Melville are briefly excerpted from Dora Smith’s
anthology, American Experience: Nonfiction. New
York: MacMillan, 1984.
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Introduction
Getting to Know
Logical Fallacies
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What’s a logical fallacy and
why should you care?
• It’s poor logic partly consisting of
overgeneralizations and assumptions.
• The presence of logical fallacies may weaken a
writing project. When you’re developing an
argument, your points should follow in logical
order and make proper conclusions.
• When you’re refuting a counterargument
(procatalepsis), it’s useful to point out logical
fallacies as weak points in your opponent’s
argument.
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Logical Fallacies:
Several Examples
• non sequitor: reasoning doesn’t hold together,
"doesn't follow“
• bandwagon: recommends a course of action
just because “everyone else” is doing it
• equivocation: ambiguity
• either/or: false binaries
• faulty generalization: inadequate evidence &
jumps to conclusions
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Logical Fallacies:
More Examples
• faulty causal: cause & effect problem
• faulty analogy: analogy does not hold;
compared parts dissimilar
• begging the question: circular
reasoning & tautological definitions
• ad hominem: argument switches to
character slander
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Logical Fallacies:
Still More Examples
• ad populum: appeals to irrational fears
& prejudices
• red herring: dodges main issue (refers
to red herring dragged across the paths
of hounds to throw them off in their
pursuit)
• complex question: two-pronged
question "When did you stop stealing?"
(combines two questions, one implied)
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Now You Try It!
For the next group of slides, identify the
logical fallacy at work in each. You may
choose among these terms: non
sequitor, equivocation, faulty
generalization, bandwagon, faulty
causal, faulty analogy, begging the
question, ad hominem, ad populem,
red herring, and complex question.
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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).
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Answers
• “ ‘Either they voted for the candidate or they
voted 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 the Logical Fallacy
•
“ ‘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).
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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 everybody
cheat a little bit’ ” (Corbett and
Connors 70)?
•
“ ‘Why did you steal the diamond
ring’ ” (Corbett and Connors 71)?
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Answers
• “ ‘You accuse me of cheating on my income tax, but
doesn’t everybody cheat a little bit’ ” (Corbett and
Connors 70)?
RED HERRING
OR FAULTY GENERALIZATION
• “ ‘Why did you steal the diamond ring’ “ (Corbett and
Connors 71)? COMPLEX QUESTION
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Detecting Logical Fallacies:
Examine this Excerpt
“But it is not meant that all American
writers should studiously cleave to
nationality in their writings; only this, no
American writer should write like an
Englishman or a Frenchman; let him write
like a man, for then he will be sure to
write like an American. Let us away with
this leaven of literary flunkeyism towards
England” (Melville 275).
Melville, Herman. “Hawthorne and His Mosses.” American Experience: Nonfiction. Dora Smith, Gen. Ed.
New York: MacMillan, 1984. 269-277.
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Detecting Logical Fallacies:
Examine this Excerpt
“Turn, now, to politics. Consider, for example, a campaign
more uproariously idiotic – a deafening, nerve-wracking
battle to the death between Tweedledum and Tweedledee,
Harlequin and Sganarelle, Gobbo and Dr. Cook – the
unspeakable, with fearful snorts, gradually swallowing the
inconceivable? I defy anyone to match it elsewhere on the
earth. In other lands, at worst, there are at least intelligible
issues, coherent ideas, salient personalities. Somebody
says something, and somebody replies. But what did
Harding say in 1920, and what did Cox reply? Who was
Harding, anyhow, and who was Cox? Here, having
perfected democracy, we lift the whole combat to symbolism,
to transcendentalism, to metaphysics. Here we load a pair
of palpably tin cannon with blank cartridges charged with
talcum powder, and so let fly” (Mencken 388).
Mencken, H. L. “On Being an American.” Dora Smith, Gen. Ed. American Experience: Nonfiction.
New York: MacMillan, 1984. 385-389.
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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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The Writing Center
For more help with logical fallacies,
contact the Writing Center.
• Where: 2nd Floor of Scott Academic Center
• When: 8 a.m. to 5 p.m., Monday through Friday
• How: Drop by in person, call x426, or
e-mail Dr. Lee at <[email protected]>.
• What else: Thanks for your interest in our
resources!
“Faith and knowledge resting on the hope
of eternal life . . .” (NIV, Titus 1.2).
Version Date: 3.10.06, [email protected],
Colossians 2.8