Common Fallacies in Reasoning

Dr. Gass

HCOM 235

Spring 2009

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COMMON FALLACIES IN REASONING

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1. FAUL= TY CAUSE: (post hoc ergo propter hoc) mistakes correlation or association for causation, by assuming that because one thing follows another it was caused by the other.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: A black cat crossed Babbs' path yesterday and, sure enough, she was involved in an automobile accident later that same afternoon.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: The “B= ambino curse” claimed that the Boston Red Sox could never win the world seri= es because they traded Babe Ruth to the Yankees in 1920. After an 80 year draught, however,= the Red Sox finally won a world series in 2004, thus breaking the curse.

2. SWEE= PING GENERALIZATION: (dicto simpliciter) ass= umes that what is true of the whole will also be true of the part, or that what = is true in most instances will be true in all instances.

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<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Muffin must = be rich or have rich parents, because she belongs to ZXQ, and ZXQ is the riche= st sorority on campus.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: I'd like to = hire you, but you're an ex‑felon and statistics show that 80% of ex‑= felons are recidivists.

3. HASTY GENERALIZATION: bases an inference on too small a sample, or on an unrepresentative sample. Often, a single example or instance is used as the basis for a broa= der generalization.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Movie stars = are really rude. I asked Matthew McConaughey for his autograph in a restaurant in Westwood the other evening, and he told me to “get lost.”

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Pit Bulls are actually gentle, sweet dogs. = My next door neighbor has one and his dog loves to romp and play with all the = kids in the neighborhood!

4. FAUL= TY ANALOGY: (can be literal or figurative) assumes that because two things, events, or situations are alike in some known respects, that they are alike in other unknown respects.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: What's the b= ig deal about the early pioneers killing a few Indians in order to settle the West? After all, you can't make an omelet without breaking a few eggs.=

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Banning the = sale of “bongs” on the Internet to curb drug use makes about as much sense as banning bikini sales to reduce promiscuity.

5. APPE= AL TO IGNORANCE: (argumentum ad ignorantiam) att= empts to use an opponent's inability to disprove a conclusion as proof of = the validity of the conclusion, i.e. "You can't prove I'm wrong, so I must= be right."

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: We can safely conclude that there is intelligent life elsewhere in the galaxy, because th= us far no one has been able to prove that there is not.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: The new form= of experimental gene replacement therapy must be working. Not a single patient has returned = to complain!

6. BIFURCATION: (either‑or, black or white, all or nothing fallacy) assumes that two categories are mutually exclusive and exhaustive, that is, something is eit= her a member of one or the other, but not both or some third category.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Either you f= avor a strong national defense, or you favor allowing other nations to dictate our foreign policy.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Either you a= re with the terrorists or you are with the United States.

7. FALSE DILEMMA: (a form of bifurcation) implies that one of two outcomes is inevitable, and both have negative consequences.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Either you b= uy a large car and watch it guzzle away your paycheck, or you buy a small car and take a greater risk of being injured or killed in the event of an accident.=

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: You can put = your money in a savings account, in which case the IRS will tax you on the inter= est, and inflation will erode the value of your money, or you can buy stocks and watch your 401k fall like a sack of hammers.

8. FAUL= TY SIGN: (also includes argument from circumstance) wrongly assumes that one event or phenomenon is a reliable indicator or predictor of another event or phenome= non.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: the cars dri= ving in the opposite direction have their lights on; they must be part of a fune= ral procession.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: The Boswell’s must be home. The lights are on upstairs.=

9. DAMN= ING THE SOURCE: (ad hominem, sometimes called the genetic fallacy) attempts to refute an ar= gument by indicting the source of the argument, rather than the substance of the argument itself.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: There is no = reason to listen to the arguments of those who oppose school prayer, for they are = the arguments of atheists!

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Candidate __________ never served in the armed forces and we don’t want a coward for our Commander in Chief.

10. TU QUOQUE: (look who's talking or two wrongs make a right) pointing to a similar wrong= or error committed by another.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Gee, Mom and= Dad, how can you tell me not to smoke grass when you both smoke cigarettes and d= rink alcohol?

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: The United S= tates has no business criticizing the human rights policies of Third World nation= s, not as long as discrimination and segregation continue to exist in the United States.

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11. EQUIVOCATION: allows a key word or term in an argument to shift its meaning during the course of the argument. The result is that the conclusion of the argume= nt is not concerned with the same thing as the premise(s).

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Only man is = rational. No woman is a man. Therefore, no woman is rational.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: No one who h= as the slightest acquaintance with science can reasonably doubt that the miracles = in the Bible actually took place. Every year we witness countless new miracles= in the form recombinant DNA, micro‑chips, organ transplants, and the lik= e. (note: the word "miracle" does not have the same meaning in each case)

12. BEG= GING THE QUESTION: (petitio principii) ent= ails making an argument, the conclusion of which is based on an unstated or unpr= oven assumption. In question form, this fallacy is known as a COMPLEX QUESTION.<= o:p>

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Abortion is murder, since killing a baby is an act of murder.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Have you sto= pped beating your wife?

13. TAUTOLOGY: (a sub-category of circular argument) defining terms or qualifying an argum= ent in such a way that it would be impossible to disprove the argument. Often, = the rationale for the argument is merely a restatement of the conclusion in different words.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: The Bible is= the word of God. We know this because the Bible itself tells us so.<= /span>

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: You are a disagreeable person and, if you disagree with me on this, it will only furt= her prove what a disagreeable person you are.

14. APP= EAL TO AUTHORITY: (ipse dixit also called ad verecundiam sometimes) attempts= to justify an argument by citing a highly admired or well‑known (but not necessarily qualified) figure who supports the conclusion being offered.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: If it's good enough for (insert celebrity's name here), it's good enough for me.<= o:p>

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Laws against marijuana are plain silly. Why, Thomas Jefferson is known to have raised he= mp on his own plantation.

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15. APP= EAL TO TRADITION: (don't rock the boat or ad verecund= iam) based on the principle of "letting sleeping dogs lie". We should continue to do things as= they have been done in the past. We shouldn't challenge time-honored customs or traditions.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Of course we= have to play "pomp and circumstance" at graduation, because that's = always been the song that is played.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Why do I mak= e wine this way? Because my father made wine this way, and his father made wine th= is way.

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16. APP= EAL TO THE CROWD: (ad populum or playing to the gallery) refers to popular opinion or majority sentiment in order to provide support for a claim. Often the "common man" or "common sense" provides the basis for the claim.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: all I can sa= y is that if living together is immoral, then I have plenty of company.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Professor Windplenty's test was extremely unfair.&nb= sp; Ask anyone who took it.

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17. STR= AW MAN: stating an opponent's argument in an extreme or exaggerated form, or attack= ing a weaker, irrelevant portion of an opponent's argument.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: A mandatory = seat belt law could never be enforced. You can't issue citations to dead people.=

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: What woman i= n her right mind could truly desire total equality with men? No woman wants the r= ight to be shot at in times of war, the right to have to pay alimony, or the rig= ht to have to develop prostate cancer.

18. SLI= PPERY SLOPE: (sometimes called a snowball argument or domino theory) suggests that if one step or action is taken it will invariably lead to similar steps or actions, the end results of which are negative or undesirable. A slippery slope always assumes a = chain reaction of cause-effect events which result in some eventual dire outcome.=

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: If the Supre= me Court allows abortion, next think you know they'll allow euthanasia, and it won't be long before society disposes of all those persons whom it deems unwanted or undesirable.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: If I let one student interrupt my lecture with a question, then I'll have to let others = and, before long, there won't be any time left for my lecture.=

19. APP= EALING TO EXTREMES: A fallacy very similar to slippery slope, which involves taking an argument= ative claim or assertion to its extreme, even though the arguer does not advocate= the extreme interpretation. The difference between the two fallacies is that appealing to extremes does not necessarily involve a sequence of causal connections.

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Husband to ex-wife: Well, if you want to be completely fair about dividing everything up, you should get one of my testicles and I should get one of y= our breasts!

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Debtor to creditor: Hey, you've already repossessed my car and my television. Why don't you just draw a quart of = blood or carve a pound of flesh from my heart too?

20. HYPOTHESIS CONTRARY TO FACT: This fallacy consists of offering a poorly supported cl= aim about what might have happened in the past or future if circumstances or co= nditions were other than they actually were or are.= The fallacy also involves treating hypothetical situations as if they were fact.

<= span class=3DGramE>e= xample: If Al Gore had won = the 2000 presidential election we wouldn’t have a global warming problem.=

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: If Hitler ha= d not invaded Russia and opened up two military fronts, the Nazis would surely have won the war.=

21. NON SEQUITUR: (literally means "does not follow") in a general sense any argume= nt which fails to establish a connection between the premises and the conclusi= on may be called a non-sequitur. In practice, however, the label non-sequitur tends to be reserved for argument= s in which irrelevant reasons are offered to support a claim. =

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: Both crime v= ictims had tattoos, so the perpetrator must have something against people with tattoos.

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<= span class=3DGramE>e= xample: Mr Boswell couldn't= be the person who poisoned our cat, Truffles, because when I used to take Truf= fles for walks he always smiled and said "Hi neighbor" when we walked = by.

22. RED HERRING: attempting to hide a weakness in an argument by drawing attention away from= the real issue. A red herring fallacy is thus a diversionary tactic or an attem= pt to confuse or fog the issue being debated.= The name of the fallacy comes from the days of fox hunting, when a herring was dragged across the trail of a fox in order to throw the dogs off the scent.

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<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: accused by h= is wife of cheating at cards, Ned replies "Nothing I do ever pleases you. I spent all last week repainting the bathroom, and then you said you didn't like the color."=

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: There's too = much fuss and concern about saving the environment. We can't create an Eden on earth. And even if we could, remember Ada= m and Eve got bored in the Garden of Eden anyway!

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23. APPEAL TO CONSEQUENCES: Cites the desirability or undesirability of the consequences of an argument as the proof that the argument is good or bad. An arguer who favors the outcome o= f an argument might assume the argument is a good one. An arguer who opposes the outcome = of an argument might assume the argument is a bad one.

example: A student tells a professor, “I know my term paper deserves at least a ‘C’ because if I don’t get a ‘C’ in your clas= s I won’t graduate.”

<= span style=3D'mso-bidi-font-size:12.0pt;font-family:Arial'>example: “Using= a cell phone can’t pose a health risk, because there is no way I can function without one.”

24. INCONSISTENCY: advancing an argument that is self-contradicto= ry, or that is based on mutually inconsistent premises.

example: A used car salespersons sa= ys, "Hey, you can’t trust those other car salesman. They’ll say anything to get you to buy a car from them."

example: A parent has just read a c= hild the story of Cinderella. The child asks, "If the coach, and the footme= n, and the beautiful clothes all turned back into the pumpkin, the mice, and t= he rags, then how come the glass slipper didn’t change back too?" [= the child is pointing out an inconsistency in the story]

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