Unit 1A
Recognizing Fallacies
LOGIC
Logic is the study of the methods and principles
of reasoning.
ARGUMENT
In this course, the term argument refers to
reasoned or thoughtful processes.
Specifically, an argument uses a set of facts or
assumptions, called premises, to support a
conclusion.
FALLACIES
A fallacy is a deceptive argument—an argument
in which the conclusion is not well supported by
the premises.
FALLACY STRUCTURES
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Appeal to Popularity
False Cause
Appeal to Ignorance
Hasty Generalization
Limited Choice
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Appeal to Emotion
Personal Attack
Circular Reasoning
Diversion
Straw Man
APPEAL TO POPULARITY
The fallacy of appeal to popularity (or appeal to
majority) uses the fact that large numbers of
people believe or act some way as evidence that
the belief is correct. That is, many people believe
p is true; therefore . . . p is true.
EXAMPLE: Microsoft makes the best
computer operating system. After all, more
people use Windows than any other operating
system.
FALSE CAUSE
The fallacy of false cause uses the fact that one
event came before another as evidence that the
first event caused the second event. That is, A
came before B; therefore . . . A caused B.
EXAMPLE: Jane took some cold medication
before her math test. She made a 100 on the test.
The cold medication made Jane ace her math
test.
APPEAL TO IGNORANCE
The fallacy of appeal to ignorance uses
ignorance (lack of knowledge) about the truth of a
proposition to concluded the opposite. That is,
there is no proof that p is true; therefore . . . p is
false.
EXAMPLE: Scientist have not found any
evidence of Bigfoot. Therefore, anyone who
claims to have seen Bigfoot must be hallucinating.
HASTY GENERALIZATION
The fallacy of hasty generalization draws a
conclusion from an inadequate number of cases or
cases that have not been sufficiently analyzed.
That is, A and B are linked a few times;
therefore . . . A causes B (or vice versa).
EXAMPLE: Three cases of brain cancer have
occurred in people who use cell phones.
Therefore, cell phones must cause these illnesses.
LIMITED CHOICE
The fallacy of limited choice (or false dilemma)
artificially precludes choices that ought to be
considered. That is, p is false; therefore . . . only
q can be true.
EXAMPLE: “You don’t support the President,
so you are not a patriotic American.”
APPEAL TO EMOTION
The fallacy of appeal to emotion uses a positive
emotional response to as a tool of persuasion.
That is, p is associated with a positive emotional
response; therefore . . . p is true.
EXAMPLE: In a commercial for Michelin tires, a
picture of a baby is shown with the words
“because so much is riding on your tires.”
PERSONAL ATTACK
The fallacy of personal attack (ad hominem)
uses a dislike of a person or group making an
argument to conclude the argument is not valid.
That is, I have a problem with the person or group
claiming p; therefore . . . p is not true.
EXAMPLE: There is no way Senator Smith’s bill
can help the cause of gun control because he is
one of the biggest recipients of campaign
contributions from the National Rifle Association.
CIRCULAR REASONING
The fallacy of circular reasoning just restates the
premise in different words. That is, p is true; p is
restated in different words.
EXAMPLE: Schools must implement a zero
tolerance policy toward drug use, because any
tolerance of drugs is unacceptable.
DIVERSION
The fallacy of diversion (or red herring) diverts
the attention from one issue to another (related)
issue. That is, p is related to q and I have an
argument concerning q; therefore . . . p is true.
EXAMPLE: We should not drill for oil in the
Alaskan National Wildlife Refuge (ANWR),
because we have too many gas-guzzling
automobiles as it is.
STRAW MAN
The fallacy of straw man makes an argument
based on a distortion of someone’s ideas or
beliefs. That is, I have an argument concerning a
distorted version of p; therefore . . . I hope you are
fooled into concluding that I have an argument
concerning the real version of p.
EXAMPLE: See Exercise 36 on page 20.