Information that is distorted or misrepresented can undermine rather than enhance an argument. Fallacies, flaws in reasoning that lead to illogical statements, are based on a false or invalid reference.

Most fallacies masquerade as logical statements, but they are really attempts to manipulate readers by influencing their emotions rather than their intellects, reaching their hearts rather than their heads.

Twenty minutes after class has begun, Jon rushes into the classroom. Rather than quietly taking his seat or handing the teacher a pass, he blurts, "I got caught in rush hour traffic. That's why I am late." Seeing the look on his teacher's face, he adds, "Sorry."

Should Jon's statement be accepted as logical? No.

This is an example of a CAUSAL FALLACY of logic. He is blaming heavy traffic for his tardiness. Since he lives in the area, he knows the traffic pattern and can listen on the radio for traffic reports. What he has failed to acknowledge is the time of his departure from home.

Below are some often used fallacies of logic. Don't use them and be aware when others are using them. Test your knowledge with the Fallacies of Logic Quiz. Also check out more vocabulary terms related to logic, as well as the student model of a fallacious editorial. How many fallacies of logic can you find?

• AD HOMINEM - (arguing against the person) diverting attention to the person advocating the opposite position, usually with disparaging statements, instead of dealing with the issue:

  "Sure prison reform sounds great - until you realize the man proposing it is an ex-con."

• ARGUING IN A CIRCLE - one assumes the truth of a premise, draws a conclusion from the premise, and then uses the conclusion to prove the initial premise:

"Boxing is a dangerous sport because it is unsafe."
"Unsafe" conveys the same idea as "dangerous" thus the speaker has not proven that danger exists.

ALSO CALLED: Begging the question, circular argument, petitio principi

• BANDWAGON - implies something is right because everyone is doing it:

"Smoking must not be bad for people. Millions of people smoke."

• BEGGING THE QUESTION - one assumes the truth of a premise that is supposed to be proven in the argument:

  "Arnold Schwarzenegger was the best actor for the role because there's just no one else who's better."
  Compare the previous statement to this one which is a valid statement:
  "They signed Arnold Schwarzenegger to play the lead because Hollywood can't make an action movie without a big star."

ALSO CALLED: Arguing in a circle

• CARD STACKING - states only those facts that support the point being made and ignores all other important evidence:

a person arguing for term limits only presents the failures of those who serve more than three terms

• EITHER-OR FALLACY - gives only two alternatives when more exist, thus oversimplifying the issue:

"Either go to college or forget about getting a job."

• FALSE ANALOGY - a comparison in which the differences outweigh the similarities or assuming if two things are alike in one or a few ways, they are alike in all ways:

  "Old Joe Smith would never make a good president because an old dog cannot learn new tricks."
  Home-spun analogies like this often seem wise, but just as often they fall apart when examined. Learning the role of president does not compare to a dog's learning new tricks.

• FALSE OR IRRELEVANT AUTHORITY - cites an authority or "expert" who has no claim to expertise about the subject. This fallacy attempts to transfer prestige from one area to another:

an actor who portrays a doctor on television in a commercial touts vitamin supplements

• FALSE CAUSE/CAUSAL - confusing chronology with a cause-effect relationship:

  A preceded B, therefore A caused B.

ALSO CALLED: Post hoc, post hoc ergo propter hoc ("after this, therefore because of this")

• HASTY GENERALIZATION - draws a broad conclusion from inadequate evidence. Stereotyping is a form of hasty generalization:

"Everyone from county Y is dishonest."

• NON-SEQUITUR - (it does not follow) provides evidence which does not really prove the point:

"Jane Jones is a forceful speaker, so she would make a good mayor."

• RED HERRING - sidetracks an issue by presenting a totally unrelated issue:

  "Why worry about pandas becoming extinct when we should be worried about the homeless?"
  Someone who introduces an irrelevant issue hopes to distract the reader just as red herring can distract bloodhounds from a scent.

ALSO CALLED: Ignoring the question

• SLIPPERY SLOPE - uses one weakness in a position to assume that the whole is doomed to failure. The sheer negativity of the possible effects is supposed to persuade:

  "We have to win in Vietnam or the entire Southeast will become Communist."

  ALSO CALLED: Domino theory

• STRAW MAN - oversimplifies to make a choice seem obvious, relies on creation of a false image of someone else's statements, ideas, beliefs:

  "My opponent believes that higher taxes are the only way to pay for needed improvements. She has never met a tax she didn't like."

• SWEEPING GENERALIZATION - overly general statement which needs to be qualified by words or phrases such as "some," "few," "many," "most," "usually," or "sometimes":

  "You will die if that mosquito bites you."
  In fact mosquito-borne diseases infect up to 700 million people each year, killing more than 2 million. However, in the United States, sophisticated medicine and mosquito-control efforts have made such diseases extremely rare.