LOGICAL FALLACIES

 

A widely accepted aspect of logic and critical thinking instruction includes the study of formal and informal fallacies. We have seen some of the formal ones in our study of deductive logic. According to The New Shorter Oxford English Dictionary, the word “fallacy” is derived from the Latin words fallax, which means deceptive, and fallere, which means to deceive. Here are the definitions:

1. a. Deception, guile, trickery; a deception; a lie.

b. Deceptiveness, unreliability.

2. A deceptive argument, a sophism.
3. An error, esp one founded on false reasoning. Also, delusion, error.
4. Fallibility.
5. Unsoundness of opinion, an argument, etc.; delusiveness, disappointing character.

 

In the development of logic and critical thinking theory, a number of deceptive, false and/or unsound reasoning patterns have been identified and named. We will be looking at twenty-four of these so-called “informal fallacies.” Some scholars identify many more, and I have chosen these based in part on what’s included in your textbook, and in part on my own consideration of which ones are important to include. The study of the informal fallacies will form the basis of your group assignment, later in the course. You should read the descriptions of the fallacies in the textbook, when available. In addition, I am providing other examples and descriptions from other resources. You can also look them up on the Internet for more clarification.

 

The patterns of reasoning in these fallacies may appear to provide support for a conclusion, but actually do not. This list includes many more than the limited number included in your textbook, and we will be discussing them in class. 

 

Index of fallacies:

 

1.      Attacking the Person

2.      Appeal to Ignorance

3.      Appeal to Authority

4.      Amphiboly

5.      Appeal to Emotion

6.      False Analogy

7.      Begging the Question

8.      Slippery Slope

9.      Common Belief

10.  Past Belief

11.  Contrary-to-Fact Hypothesis

12.  Division

13.  False Dilemma

14.  Equivocation

15.  Far-Fetched Hypothesis

16.  Hasty Generalization

17.  Post Hoc Ergo Propter Hoc

18.  Inconsistency

19.  Non sequitur

20.  Questionable Cause

21.  Red Herring

22.  Slanting

23.  Straw Man

24.  Two Wrongs Make a Right

 

1. Ad hominem or Attacking the Person: In this fallacy, the messenger is killed, rather than examining the merits of the premises and conclusion of the argument. Examples:

 

Friedrich Nietzsche’s philosophy is not worth the paper it’s printed on. Nietzsche was an immoral reprobate who went completely insane from syphilis before he died.

 

Publishing magnate Steve Forbes has argued at length that the fairest kind of income tax is a flat tax. But Forbes is a billionaire, and he stands to save millions of dollars if a flat tax is enacted. Therefore, we can hardly take Forbes’ arguments seriously.

 

The first example attempts to claim that since Nietzsche was “an immoral reprobate” who “went completely insane from syphilis” that we should not examine his philosophical arguments on their own merits. However, neither a person’s character nor mental state are necessarily relevant to an analysis of how well premises supports conclusions, and whether or not the premises are true. In the second example, just because someone stands to gain from the outcome of an argument he or she is presenting, it does not mean that the argument itself is weak. Once again, the analysis of an argument requires examining the relationship between the premises and the conclusion, and then determining the truth of the premises.

 

2. Ad ignorantium, Argument from Ignorance, or Appeal to Ignorance: This form of fallacious reasoning attempts to claim that a conclusion is true because it cannot be proved false, or that a conclusion is false because it cannot be proved true. Examples:

 

People have been trying for centuries to disprove the claims of astrology, and no one has ever succeeded. Therefore, we must conclude that the claims of astrology are true.

 

No one has ever seen Mr. Andrews drink a glass of wine, beer, or any other alcoholic beverage. It is probably true that Mr. Andrews is a nondrinker.

 

Just because we cannot prove that astrology is false, does not mean that it is true. Even though no one has ever seen him drink, it does not follow that he does not. Good arguments must provide support for the conclusion, not just show that there is no support for the alternative conclusion.
 

3. Ad verecuniam, Appeal to Authority, or False Authority: This fallacy tries to convince the listener by appealing to the reputation of a famous or respected person. Oftentimes it is an authority in one field who is speaking out of his or her field of expertise. Example: Sports stars selling cars or hamburgers. Or, the actor on a TV commercial that says, "I'm not a doctor, but I play one on TV." Everyone wants to “Be like Mike,” and so they buy the shoes that he endorses, drink the sports drinks that he advocates, etc. But is Michael Jordan an authority on shoes or sports drinks? In life, we must rely on authorities to inform and educate us. After all, you are all assuming that I am an authority on critical thinking, right? This fallacy is not committed when supporting conclusions based on what legitimate authorities might say. It is committed when using an authority to support a conclusion that is outside his or her expertise, or when the credibility of the expert is suspect for some reason. Examples:

 

Dr. Bradshaw, our family physician, has stated that the creation of muonic atoms of deuterium and tritium hold the key to producing a sustained nuclear fusion reaction at room temperature. In view of Dr. Bradshaw’s expertise as a physician, we must conclude that this is indeed true.

 

James W. Johnson, Chairman of R.J. Reynolds Tobacco Company, testified before Congress that tobacco is not an addictive substance and that smoking cigarettes does not produce any addiction. Therefore, we should believe him and conclude that smoking does not in fact lead to any addiction.

 

Dr. Bradshaw may be an expert in medicine, but he is not an expert in atomic physics. Given that Mr. Johnson would open his company up to lawsuits if he admitted to nicotine’s addictive properties, we cannot trust him to tell the truth about this, even though he could be considered to be an expert about tobacco. Why doesn’t what I just said commit the Ad hominem fallacy?

 

4. Amphiboly: This fallacy relies on ambiguities that result from the structure of a sentence, rather than ambiguity in a word’s meaning. These can sometimes be the result of a misplaced modifier. For example:

 

Professor Johnson said that he will give a lecture about heart failure in the biology lecture hall. It must be the case that a number of heart failures have occurred there recently.

5. Appeal to Emotion: In this type of fallacy, the arguer attempts to persuade someone by playing on his or her sympathies, fears, vanity, anger or other emotions, rather than providing legitimate premises that support the conclusion. The fallacy can appeal to various emotions including pity, pride, fear, hate, vanity, or sympathy. Generally, the issue is oversimplified to the advantage of the arguer. As an instructor, I have occasionally heard something like the following:

 

“I am sorry, Mr. Campbell, but I could not turn in my essay that is due today because my little sister stubbed her toe, and the only thing I had to wipe up the blood was my report on the Marquis de Sade. I printed out a new copy but then I had to check the oil in my car on the way to class, and the gas station was out of paper towels. So, I had to use the report to wipe off the dipstick. I know that you don’t want to get a reputation of being a mean instructor, so please be so kind as to let me turn it in next week.”
 

6. False Analogy: While using analogies in arguments is frequently legitimate, this fallacy occurs when the two things being compared are not sufficiently alike in the relevant aspects. Consider the following:
   
               The planet Mars possesses an atmosphere with clouds and mists resembling our own; it    has seas distinguished from the land by a greenish color, and polar regions covered with            snow. The red color of the planet seems to be due to the atmosphere, like the red color of       our sunrises and sunsets. So much is similar in the surface of Mars and the surface of the Earth that we readily agree that there must be inhabitants there as here.--W. S Jevons,   Elementary Lessons in Logic.
   
   Earth and Mars are being compared favorably; however, the facts don't support the analogy. We now know that Mars has no seas and no earth-like atmosphere. While there might be some similarities, they are not sufficient to justify the conclusion that Mars must have inhabitants like Earth does.

 

Two more examples:

 

ð        This must be a great car, for, like the finest watches in the world, it was made in Switzerland.

ð        I wish to protest the article written by Mr. Middleton. Can Mr. Middleton be so naïve as to really believe that banning ownership of firearms would significantly reduce murders and robberies? Did banning booze significantly reduce drinking? (Taken from a reader’s response to a 1975 Saturday Review article.)

Here is the analysis of the author of the book from which I took this: “This example is a typical argument from analogy. The plausible premise that would be accepted by the average reader is that prohibition did not, in fact, work as a measure to reduce drinking. The analogy or comparison premise is that banning ownership of firearms is similar to banning consumption of alcohol. (However) liquor, beer, and wine are easy to make at home (or other more-or-less surreptitious locations), therefore prohibition was difficult to enforce. However, it would be difficult to manufacture guns secretly, or at home, and easier to police distribution of guns. Hence, the reasons prohibition failed do not apply to the case of gun control. (Thus) the argument is a case of faulty analogy” (paraphrased from Walton, Douglas N. Informal Logic. pp. 261-2).
 

7. Begging the Question: There are different kinds of this fallacious form: circular reasoning and conclusion contained in the premise. Another, perhaps, more subtle variety occurs when someone leaves out a crucial premise, with the appearance that the evidence given is sufficient to prove the conclusion. Examples:

 

Murder is morally wrong. This being the case, it follows that abortion is morally wrong.

 

Capital punishment is justified for the crimes of murder and kidnapping because it is quite legitimate and appropriate that someone be put to death for having committed such hateful and inhuman acts.

 

In the first instance, there is a missing and questionable premise: Abortion is murder. While some clearly believe this, it is at least a debatable issue. The argument begs the question of whether or not abortion is murder. With the second example, to say that something is “legitimate and appropriate” is to say that it is “justified.” So, in essence, the argument claims that capital punishment is justified because it is justified.
 

8. Slippery Slope: This fallacy is committed when someone attempts to argue that a single step down the proverbial garden path will inexorably and inevitably lead to the bottom of a deep chasm. While it may be controversial to say so, I frequently hear many arguments opposing drug use committing this fallacy. Advocates of the drug war sometimes assert that smoking marijuana leads people to try more addictive and more dangerous drugs. Once someone tries marijuana, the next step is cocaine. After they become habituated to cocaine, these drug addicts move on to methamphetamine and heroin. These people then become criminals in order to support their habits. As criminals, they steal from law-abiding citizens, and assault and kill innocent victims. They have no regard for morality and legality. The result is social and political chaos. In other words, smoking marijuana leads to anarchy. This is a slippery slope fallacy.
    
9. Common Belief: This is the “everybody knows…” fallacy. Just because a lot, or even all, people believe something, it does not make it true. Even though we all know that OJ killed his wife, it does not follow that he actually did.
    
10.  Past Belief: This is the “everybody has always known…” fallacy. Obviously, it is just a twist on the common belief fallacy. Just because something has been believed or thought for a long time, or because it was once believed, it is not sufficient to justify it as true. After all, there was a time when literally everyone thought that the earth was flat. Some of our most widely held current beliefs may turn out to be of this variety.

More on Common Belief and Past Belief: There is an international organization that is committed to propagating a currently unpopular belief: http://www.alaska.net/~clund/e_djublonskopf/Flatearthsociety.htm. While this belief is no longer accepted, it was once a very common belief. Nevertheless, its commonality did not make it true. Just because many people believe something to be true, it does not make it so. While it is a common belief the world over that God exists, the belief does not prove that she does.
 

11.  Contrary-to-Fact Hypothesis: In this fallacy, we take a factual situation and claim that if different things had happened then it would not have turned out as it did. The problem here is that things may or may not have turned out any differently—we cannot know for sure. Examples:

 

If only I had completed college when I was younger, I would have a better job and be making more money today.

 

Had the United States seen things through and gotten rid of Saddam Hussein when we had the chance, we would not be having the troubles we are having with Iraq today.

I taught you logic. So, if I hadn’t taught you logic, you never would have learned logic at all.

 

In this country, citizens are permitted to own guns. Therefore, if guns were outlawed, citizens would be unable to protect themselves and there would be an uncontrollable crime wave.

 

I wouldn’t be getting these low grades if I went to Sonoma State.

 

Maybe you’d have a better job, but maybe not. Maybe things would be different in Iraq, and maybe not. Perhaps someone else would teach you logic. No one knows for sure what would happen if guns were outlawed. Perhaps you would be getting lower grades?
 

12. Division: The claim here is that if the whole thing’s got it, then each of the parts must as well. Examples:

 

Salt is a nonpoisonous compound. Therefore, its component elements, sodium and chlorine, are nonpoisonous.

 

Harvard is one of the top-ranked educational institutions in the world. So, the anthropology department must have the best teachers.

           

Chlorine by itself is quite poisonous to us human beings. Lots of factors go into ranking educational institutions, and some departments of a highly ranked university may not themselves be highly ranked.
 

13. False Dilemma (often called the either/or fallacy, Black & White fallacy, or false dichotomy): Fallacies of this type will usually have an explicit or implied “either/or” included, and imply that the two alternatives presented are the only ones available. They assume that we must choose one of two alternatives instead of allowing for other possibilities; a false form of disjunctive syllogism. This can be a particularly subtle to detect, but quite simple if you just look for situations where only two possibilities are presented, and then see if in fact they are the only ones.
    
    Either you use Ultra Guard deodorant or you risk the chance of perspiration odor. Use Ultra Guard!
    
    Either I continue smoking, or I’ll get fat and no one will be interested in being with me.
    
    Obviously no one wants to “risk the chance of perspiration odor.” Therefore, there is only one other alternative: Use Ultra Guard. Even though people might think that if they stop smoking they will get fat, it is possible to stop and not gain weight.

 

More examples:

 

ð       America—love it or leave it!

ð       Either you’re with us or your against us.

ð       We must attack Iraq or Saddam will develop WMD.

ð       The U.N. must vote for war or face irrelevance.

ð       Either we support this administration’s trade policy or face unfair foreign competition.

14. Equivocation: This fallacy relies on the ambiguity that is often found in the meanings of many words. The idea is to use a word in different ways in an argument, using the meanings that are most supportive of the arguer’s point of view. It is frequently difficult to spot the shift in meaning if you do not pay close attention. For instance, suppose that I claim that everyone in this country is equal. You may have heard people respond to that claim by talking about the great disparities that exist in people’s educational and economic opportunities. Such a response equivocates on the meaning of the word “equal.” My original claim meant that people have equal rights under the law, while the respondent was talking about equality of opportunity. If the different understandings of the meaning of “equal” are not brought to light, you can imagine people arguing about this forever without resolution.
    
    
15. Far-Fetched Hypothesis: Many people seem willing to accept hypotheses that are not based in factual evidence. Sometimes the acceptance can be the result of strong beliefs or attitudes, deep desires or fears, or simply lack of thinking clearly. A far-fetched hypothesis is exemplified in some late night TV ads: “Call the Psychic Connection and have one of our gifted psychics reveal the secrets about your love life, career, health, and family.” The hypothesis that people can be called on the telephone and tell anyone on the other end of the line all about his or her life has no basis in scientific theory or experiment. However, the plethora of ads for this kind of “service” seems to provide testimony that people are calling in sufficient numbers to justify the expenses of the advertising and staffing such businesses. I have occasionally wondered where they find the people to answer the phones. I know that UOP offers no training in such skills, and I have never heard of any psychic universities.
    
    
16. Hasty Generalization: With the material we have discussed on generalizations, it should be fairly simple to understand this fallacy. Typically, it involves making a general claim based on limited evidence. Since we can rarely sample all of the evidence about groups and qualities in which we are interested, we must make generalizations based on particular instances. However, there are guidelines for making legitimate generalizations that include things like:
    
                a. Making sure that the sample of particular instances is random and      unbiased;
                b. Using statistical rules to assure the sample is sufficiently large;
                c. Choosing the particular instances so that they represent the target       population.
    
    
17. Post Hoc Ergo Propter Hoc: Don’t let the fancy Latin name throw you. This is just a particular kind of questionable cause (number 20 below) in which there are two (or more) events that happened to occur near one another (in time or location) and one of these events is asserted as the cause of the other. For example:
    
                The Dallas group held a rain dance at the Turtle Creek fountain Sunday night,       and the group leader Debra Denton claimed it got results. “It rained, didn’t it?”          she asked Monday (Dallas Morning News, July 22, 1980).
    
    
18. Inconsistency: Being consistent is a basic logical tenet. Inconsistency can occur in the things people say, when, for example, they contradict themselves. Inconsistency can also be a conflict between word and deed. While it may be a woman’s prerogative to change her mind, if it results in an inconsistency of either kind, it is logically taboo. (Does my previous statement reflect any assumptions about women? Could it be a stereotype?) Parents can be guilty of inconsistency when they don’t practice what they preach to their children. Employers/managers can commit this logical faux pas when applying policies to some but not to others. Noticed any inconsistency in yourself or others lately?
    
    
19. Non sequitur: Arguments committing this type of fallacy have premises that are irrelevant to the conclusion. Technically, it means that the conclusion does not follow from the premises. For example: “Most people feel in their heart of hearts that they do/don’t (take your pick) deserve to be loved. Therefore, they do/don’t.” It does not follow from the fact that people feel something that it is true. By the way, for a little fun, there is a comic strip named after this logical fallacy, and you can find it at http://www.ucomics.com/nonsequitur/.
    
    
20. Questionable Cause: When we claim that something caused an effect to occur, we are usually saying that the cause made the effect happen, or was the reason for the effect’s occurrence. However, in examining evidence there may be a number of possible causes that either singly or in combination could produce a particular effect. What we frequently do is identify the most recent, most unusual, or most obvious event or circumstance as the cause. Determining the real cause or causes of an effect may involve very careful investigation, and if alternatives are not examined, we may be guilty of committing this fallacy. Examples:
    
                            I studied and studied for this Anthropology exam. I read all of the                           material the teacher provided and reviewed my lecture notes until 3:00                                     a.m. the morning of the exam. Nevertheless, I got a D. Obviously the                            exam was just too difficult and the teacher is an unreasonable grader.
    
                            My horoscope this morning said that I would encounter difficult                                          circumstances in my working relationships, and that I would get a                          pleasant surprise when I returned home. Sure enough, when I got to                                   work my boss dumped a week’s worth of work on my desk and                                               demanded that I get it done yesterday. Fortunately, when I got home, my               husband had a candlelight dinner waiting to celebrate our wedding                                     anniversary. Clearly, the planets and stars have a powerful impact on the                      course of my life.
    
                The first example attempts to say that the cause of the “D” grade was the difficulty of the exam and the teacher’s grading standards. What other possible causes might exist? The second one claims that the positions of planetary bodies determine the events in one’s life. Is this the best causal explanation possible? How often do people have difficulty at work, and after a hard day come home to some kind of pleasant surprise?
    
    
21. Red Herring: With this fallacy, the arguer changes the subject to avoid dealing with the issue at hand. Often the change will be subtle, for instance to another topic that is in some way related to the original issue, but not to the central argument. In order to be effective, the change must be unnoticeable. Here is an example from Patrick Hurley’s A Concise Introduction to Logic:
    
                            Environmentalists are continually harping about the dangers of                            nuclear power. Unfortunately, electricity is dangerous no matter                                     where it comes from. Every year hundreds of people are                                        electrocuted by accident. Since most of these accidents are caused                                by carelessness, they could be avoided if people would just                                           exercise greater caution.
    
                This paragraph starts out by talking about the dangers of nuclear power,            and ends us referring to people being electrocuted by accident. The       implication is that the dangers of nuclear power can be minimized if             people would just be more careful. However, the dangers of nuclear power       have little to do with accidental electrocution.
    
    
22. Slanting: “I don’t know about you, but I would prefer not to waste four hours studying logical fallacies.” Here the implication is that studying logical fallacies is a waste of time. Rather than providing an argument to support the claim, it just implies it without providing any reasons. This kind of logical fallacy is frequently effective with people who make a similar assumption—the biased slant goes by unnoticed as such.
    
    
23. Straw Man: If you can’t refute someone’s argument, attack a misrepresentation of the argument. “All those people advocating a woman’s right to choose just want to provide irresponsible teenagers with an easily accessible after-the-fact birth control option.” As far as I know, no one in the choice camp advocates this. To attack current abortion law on this basis is to erect a straw man in order to knock it down. While it might appear that the arguments of the abortion rights camp have been demolished by such claims, they are actually left unscathed.
    
    
24. Two Wrongs Make a Right: If you are a parent, chances are you have uttered the words “Two wrongs don’t make a right!” However, we sometimes hear people try to claim that since others do something wrong, it is not really wrong. How often have you heard the justification for speeding that “Everybody does it.”? How often when accused of impropriety do politicians point the finger at their accuser, as if to say, “I am not so bad—he does it too”?