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 Fallacies in Logic

Begging the Question

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?"

Red Herring

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

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.  You can probably see the problems with these claims -- they are so unbelievable that they fail to make convincing arguments.  

Straw Man

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.  

Stacked Evidence

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 pedophiles lurk in internet chat rooms, pornographic material is easy to find on the internet, and information on building bombs is available to everyone.  The 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. 

Post Hoc

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 there is no causal relationship between the claim and the support, a post hoc fallacy has occurred. 

Hasty Generalization

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

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 of an ad hominem attack.  

Guilt by Association

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."  If a young man associates with gang members, he is assumed to be a criminal.  He is guilty by association, not by deed. 

Using Authority Instead of Evidence

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

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. 

Slippery Slope

"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 the law requires women to wait twenty-four hours before having an abortion now, tomorrow it will be forty-eight hours and then women won't be able to have an abortion at all.  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. 

Creating False Needs

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. 



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This page was created on August 18, 2001.

It was last updated on January 30, 2002.