Download Fallacies in Logic

Fallacies in Logic Created by California State University, Fullerton, January 30, 2002
Begging the
Question
Red Herring
Non Sequitur
Straw Man
Stacked
Evidence
Either-Or
Post Hoc
Hasty
Generalization
The arguer provides no support; (s)he "begs the question" and restates the claim over and over by rewording it. For example
“Capital punishment deters crime because it keeps criminals from committing murder,” says the same thing twice, just in
different words. Most of all, it fails to answer the question "Is capital punishment a deterrent to crime?"
A red herring is irrelevant and misleading support that detracts audience attention away from the real argument. For
example, "I won't hire John Smith because he drives an expensive red sports car" is a red herring; the model and color of
John Smith's car have nothing to do with his qualifications for the job. Detective fiction writes use red herrings as a plot
device to throw the reader off the track of the real killer.
Non sequitur is Latin for “it does not follow” and is used when the conclusion drawn does not make sense based on the
evidence presented. Here are some examples: lazy students sit in the back of the classroom; professors who wear jeans
are easy graders; and young men with red cars are unsafe drivers. The claims are that a student's location in the classroom
indicates a willingness to work hard or not, a professor's clothes indicate his/her grading standards, and the color of one's
care reveals how one drives. .
The straw man occurs frequently in politics. It involves claiming that an opponent made an argument that (s)he never made
and then refuting it in a way that appears as though the argument has been won. For example, Candidate A makes the
claim that Candidate B said his unhealthy eating habits could interfere with his ability to do the job, when in reality Candidate
B never brought up the issue of eating habits. Candidate A goes on to refute the eating habits issue by citing the advantages
of eating healthy, which he does, and gives the appearance that he has won the argument even though this has never been
an issue. Unfortunately, by using the straw man tactic, Candidate A may convince people that he could refute Candidate B's
other arguments equally easily.
Presenting only one side of an argument that clearly has two sides creates a distorted view of the issue. This is stacking the
evidence. For example, to prove that the internet is dangerous for children, the only evidence given is that information on
building bombs is available to everyone. Access to educational resources that the internet offers is never mentioned.
When no alternative or compromise positions in an argument are acknowledged, an either-or fallacy occurs. Here are some
examples of an either-or argument: The U.S. can either have a strong military or a strong welfare program; A woman can
either work or be a mother; Graduates can either continue their education or get a full-time job. Because these arguments
fail to acknowledge that a middle-ground solution is possible in each scenario, they fail the test of logic.
This is an abbreviated form of post hoc, ergo propter hoc, a Latin phrase that means “after this, therefore because of this.” In
simple terms, post hoc is a fallacy of faulty cause. Advertisers frequently use post hoc fallacies to sell a product. Think, for
example, of the American cultural icon of the Marlboro man. He is handsome, strong, and virile. How did he get that way?
By smoking Marlboro cigarettes! Alcohol ads make similar claims -- drink Brand X beer and get the beautiful girl, wear Brand
X clothes and you'll be popular, etc. Because no causal relationship between the claim and the support, a post hoc fallacy
Jumping to a conclusion without sufficient supporting examples results in a hasty generalization and often contributes to
stereotyping. Concluding that large dogs are dangerous because one bit a child or that because some students in inner-city
schools belong to gangs, most students in those schools are gang members constitutes a hasty generalization.
Fallacies that Affect Ethos
Ad Hominem
Guilt by
Association
Using Authority
Instead of
Evidence
Ad hominem means “to the man” in Latin, and an ad hominem argument places attention on the man rather than the ideas
prejudicing the public against the individual and ignoring his/her position on the issues. Election campaigns are increasingly
focused on "the character issue" -- the idea that a candidate's character is as important, if not more important, than his/her
ideas. This focus shifts the public's attention to negative information about a candidate's personal life and away from the
issues that (s)he believes are important. Discrediting the individual in the public's eyes is the primary purpose.
An argument based on the belief that a person's character is determined by the people with whom (s)he associates falls under
the category of "guilty by association."
When a used car salesman tells you to buy a car from him because he is trustworthy, he is using authority instead of
evidence. Name-dropping instead of facts and figures in support of an argument causes this fallacy.
Emotional Fallacies
Bandwagon
Appeal
Slippery Slope
Creating False
Needs
Teenagers often use bandwagon appeal to win an argument with their parents. They need an $85 pair of shoes because
"everyone else has them" or they need to go to the party because "everyone else is going. "The argument is that everyone is
doing something, so you should too. This type of argument is also used in public promotions and ad campaigns that suggest
because most people think a certain way or buy a certain product, you should too.
"If you give them an inch, they'll take a mile" is a slippery slope argument because it implies that if we allow one thing to
happen, we will immediately begin a downward spiral to disaster. If we don't stop wasting so much paper, we will soon lose all
the forests. If we allow children to read Harry Potter books, they will want to practice witchcraft. All of these arguments point
in one direction -- it's best not to start because the end result may be disaster.
Emotional proof appeals to what people value and think they need. Advertisers often create a false sense of need in order to
sell a product. Parents who want to raise emotionally healthy children should buy Jane Doe's book. Housewives who want
shiny countertops should buy only Product X.