Some Common Fallacies

Fallacies are kinds of errors in reasoning. They are most common when people get overly emotional about an issue. The thing about fallacies is that in the heat of the moment they can seem persuasive, but they are errors in reasoning and they do not reliably lead to the truth. So you want to be on the lookout for them when considering arguments. Below is a brief list of some of the more common fallacies, along with illustrations of them. It is often helpful to look these over when trying to think about what is wrong with an argument (whether it's your own or someone else's!).

NOTE: This is the same list of fallacies and examples given in my paper "Moral Reasoning In Applied Ethics".

CRITICAL THINKING STUDENTS: If you're in a critical thinking class, be careful about going by the following definitions. Different textbooks define fallacies differently, and I have deliberately simplified some things in order to make this page more accessible to those who are not taking a critical thinking class.

Table of Contents

1. Ad Hominem Fallacy
2. Fallacy of False Cause
3. Straw Man Fallacy
4. Appeal to Ignorance
5. Appeal To Emotion
6. Slippery Slope
7. Fallacy of Equivocation
8. Appeal to Popularity
9. Appeal to Tradition

1. Ad Hominem Fallacy

An ad hominem fallacy is an argument that is directed at the person defending the argument rather than the argument itself, and thus fails to address what is at issue. There are a number of different kinds of ad hominem arguments, but we don't need to distinguish among them here. We can get an idea of how ad hominem fallacies occur with the following examples:

(Example 1) "That's what abortion is - killing innocent humans for money. Abortionists are government licensed hit men." - Charley Reese, The Daily Iberian, Nov. 20, 1998.

In Example 1, Reese resorts to name-calling, rather than seriously addressing the question of whether abortion is morally permitted, when he claims that abortionist's are "government-licensed hit men." Thus, Reese commits an ad hominem fallacy. Example 2 is more subtle:

(Example 2) "University of Virginia professor [Charlotte] Patterson, considered a leading researcher in the field, says she has reviewed 22 studies involving offspring of gays ranging from toddlers to adults. She found none convincing [sic] that the children had suffered or were more than normally inclined to be gay. [...] Conservatives discredit Patterson by pointing out that she is an acknowledged lesbian, with a presumed ideological interest in the subject she studies." - Time, Sept. 20, 1993, p. 71.

Simply because someone is a lesbian does not mean that they will not be objective or professional when reporting the results of studies of homosexuals, any more than someone's being heterosexual means that they will not be objective or professional when reporting the results of studies of heterosexuals. To claim otherwise would be to claim that no one could ever be objective when reporting a study involving sexual orientation. This argument is an ad hominem fallacy because it merely points out that Patterson may have an incentive to incorrectly report the studies she cites - it doesn't raise any issue with regard to whether her results were in fact mistaken. People have incentives to do all sorts of things that they would never actually do. For example, if someone cuts you off in traffic, you may have an incentive to shoot them (the incentive being to discharge your anger), but that doesn't mean you'll actually shoot them. It is very different to claim that someone has a motive to do something. Motives, as defined by Webster's, are something that causes a person to act. So if Patterson had a motive to lie, in Webster's sense of the term, that means she had an incentive to lie that she acted on, and this would discredit her results.

(Example 3) "Who is Sam Brownbeck, and why is he saying all those terrible things about rock lyrics? On Nov. 6, Brownbeck, an ambitious Kansas Republican ... convened a hearing billed as "An Example of Violent Music Lyrics on Youth Behavior and Well Being ..." Brownbeck's subcommittee, which supervises schools and streets in D.C., has much more important work to do, but the senator, who will run again in 1998, is clearly searching for an issue to give him national prominence." - Rolling Stone Magazine

Here, the attack is not directed so much at Brownbeck's personal traits as it is against his plans to run for senator. But again, the fact that Brownbeck is planning a run for senator and might have an incentive to push this issue never touches on the real issue: whether there is a problem with rock lyrics.

(Example 4) Jack: You should stop smoking - it's bad for you.
Jill: Look who's talking! You smoke three packs a day!

Jack's reasoning is perfectly good, while Jill commits the fallacy. Jack is being hypocritical, but that does not mean that what he says is false. Pointing out that someone is being hypocritical often seems like a persuasive refutation of what they've said, but regardless of whether Jack is a hypocrite, what he is saying is obviously true.

(Example 5) Representative Gutierrez of Illinois, arguing in Congress on July 11, 1996, replying to Republicans arguing in favor of the "Defense of Marriage Act", a bill stipulating that 'marriage' be defined as being between a man and a woman only, excluding homosexual marriages: "I now realize that my friends on the other side of the aisle aren't the least bit serious when they talk about how important it is for the federal government not to interfere in the lives of our people. I understand that they are just kidding - just teasing us - when they stress the importance of taking power out of Washington and giving it to local officials. And now I know that their biggest joke of all is that old line about family values - all that talk about encouraging people to care about and be committed to each other."

This example is more subtle, but again, what Gutierrez is doing is accusing his opponents of being hypocritical, rather than addressing the issues of hand. Thus, he commits an ad hominem fallacy.

2. Fallacy of False Cause

As with the ad hominem fallacy, there are really several different kinds of false cause fallacy. But we won't catalogue them all here. The basic problem with every false cause fallacy is that it confuses a correlation with a cause. Two events are correlated if whenever one occurs, the other occurs. Two events are causally related if one event's occurring is sufficient to make the other event occur. For instance, there is an increase in the number of brides in June, as well as an increase in the number of flies in June. But it hardly follows that the one is the cause of the other! The two events are correlated, but not causally related.

(Example 1) Utah passed a strict gun-control law, and crime there decreased. Therefore, gun-control laws decrease crime.

This is a false cause fallacy because we don't have enough information to conclude that the gun-control law caused the decrease in crime. Lots of things, including the state of the economy, the nature of the illicit drug trade, the weather (hot weather tends to result in an increase in crimes, and unusually cold weather tends to decrease them), and dozens of other factors influence the rate of crime. Until all of these factors are taken into account, we can't be sure whether the gun-control law caused the decrease in crime. Similar sorts of arguments are made for and against the death penalty, and they involve the same fallacy.

(Example 2) "An FBI study of thirty-five serial killers revealed that twenty-nine were attracted to pornography and incorporated it into their sexual activity, which included rape and serial murder." - from an anti-pornography ad

The suggestion is that pornography causes serial killers to rape and kill. But the argument is not sufficient to establish that pornography causes rape or murder. It's likely that serial rapist/murderers are obsessed with sexual acts to begin with, and it is their obsession that leads to both use of pornography and killing.

(Example 3) "In its origins [AIDS] was entirely a disease of sodomites... That the first case was diagnosed a little over a decade after the so-called "Gay Rights" and "Gay Pride" movement gained momentum and force can hardly be coincidental." - Harry Jaffa, Professor Emeritus of Political Philosophy at Claremont McKenna College

The suggestion is that since AIDS appeared in the U.S. after the Gay Pride movement, the Gay Pride movement caused AIDS. However, we know that AIDS is not caused by political demonstrations but by the HIV virus. Moreover, we know that AIDS first became an epidemic in Africa where it infected primarily heterosexuals, not homosexuals.

3. Straw Man Fallacy

A straw man fallacy occurs when (1) the arguer misrepresents their opponents view, (2) shows that the misrepresentation is mistaken, and then (3) concludes that their opponents view is mistaken. Here are some examples:

(Example 1) What I object to most about those people who oppose capital punishment is that they believe that the lives of convicted murderers are more important than the lives of the police and prison guards who protect us. But, obviously, since the lives of those who protect us are of the greatest value, no one should oppose capital punishment.

In Example 1 the opponent's view is that capital punishment is wrong. This view is then misrepresented as being the view that the lives of convicted murderers are more important than the lives of the police and prison guards. The remaining two elements of the fallacy are explicitly stated in the example. Sometimes, however, some of the elements of the straw man are implicit, as in Example 2:

(Example 2)
Consider the following claim by Rush Limbaugh:
"I'm a very controversial figure to the animal rights movement. They no doubt view me with some measure of hostility because I am constantly challenging their fundamental premise that animals are superior to human beings."

If this is followed with the argument that animals are not superior to human beings, and thus the animal rights movement is misguided, then we have an example of a straw man fallacy. The straw man is the misrepresentation of animal rights activists as holding the view that animals are superior to human beings: virtually no animal rights activists hold this view.

(Example 3) "Advocates of legalized abortion predicted it would solve our social problems. Instead, this destruction of one-fourth of a generation has left a more violent society in its wake: Child abuse has exploded, from 167,000 estimated cases in 1973 to 2.4 million in 1989, according to the National Center of Child Abuse and Neglect - a 1,400% increase. Teen suicide, among non-aborted and thus presumably "wanted" children, has doubled. Violent crime has more than doubled." - "The Post Abortion Report", published by Fresno/Madera Right to Life

The first sentence is a straw man. Did advocates of legalized abortion ever claim it would solve problems of violent crime, etc.? Insofar as the passage suggests that abortion is the cause of these various social problems, we have a false cause fallacy.

4. Appeal to Ignorance

The fallacy of appeal to ignorance occurs when someone uses an opponent's inability to disprove a claim as evidence of that claim's being true or false (or, acceptable or unacceptable). For instance, consider the following:

(Example 1) You haven't been able to prove beyond any reasonable doubt that there is no God. Therefore, it is still reasonable for me to believe in God.

However, whether it's reasonable to believe something depends on the reasons one has in its favor, not whether others have reasons against it.

5. Appeal To Emotion

Appeals to emotion occur when someone tries to manipulate another person's emotions (e.g., sympathy, pity, anger, fear, etc.) in order to get them to accept or reject an argument or view. Here are some examples:

(Example 1) Statement made by Carol Everett, a former abortion provider and now an opponent of abortion, explaining why she now opposes abortion: "Then we had a death. A 32-year-old woman hemorrhaged to death as a result of a cervical laceration. I finally realized, we weren't helping women - we were destroying them." - from an ad published by the National Right to Life

Here, Everett appeals to the reader's sympathy rather than to their reason.

(Example 2) "If you have never been born again, eternal separation from God in the Lake of Fire awaits you. If you are born again, then being with the Lord in heaven forever is your destiny. Which do you choose?" - from "Have You Been Born Again", a pamphlet handed out on the Fresno State University campus, Fall 1997

In Example 2, the authors appeal to your fear of the Lake of Fire to get you to accept their religious beliefs.

6. Slippery Slope

The slippery slope fallacy occurs when someone claims that an apparently harmless action is likely to result in a chain reaction of events (the "slippery slope") leading up to a harmful consequence, when, in fact, the chain reaction of events is very unlikely to occur.

(Example 1) "A person apparently hopelessly ill may be allowed to take his own life. Then he may be permitted to deputize others to do it for him should he no longer be able to act. The judgment of others then becomes the ruling factor. Already at this point euthanasia is not personal and voluntary, for others are acting on behalf of the patient as they see fit. This may well incline them to act on behalf of other patients who have not authorized them to exercise their judgment. It is only a short step, then, from voluntary euthanasia (self-inflicted or authorized), to directed euthanasia administered to a patient who has given no authorization, to involuntary euthanasia conducted as a part of a social policy." - J. Gay Williams, "The Wrongfulness of Euthanasia"

But it's unlikely that permitting euthanasia in a restricted set of cases is likely to result in mass unjust killings, especially in contemporary American society.

(Example 2) "I think that the use of marijuana as a medical treatment shouldn't even be considered. If we make drugs legal in a few cases, then we might eventually have to completely legalize them - which is even crazier than Proposition 215. If we want to help people out by letting them do illegal things, then let's just get rid of all our laws." - letter to editor of Newsweek, November 11, 1996.

Again, it's unlikely that drugs will be completely legalized, or that we'll get rid of all our laws, as a result of allowing marijuana to be prescribed in a limited range of cases.

(Example 3) Representative Largent of Oklahoma, arguing in Congress on July 11, 1996 in favor of the "Defense of Marriage Act", a bill stipulating that 'marriage' be defined as being between a man and a woman only, excluding homosexual marriages: "There is ... a radical element, a homosexual agenda that wants to redefine what marriage is. They want to say that a marriage not only is one man and one woman but it is two men or it is two women. What logical reason is there to keep us from stopping expansion of that definition to include three people or an adult and a child, or any other odd combination that we want to have?  ... and it does not even have to be limited to human beings by the way. I mean it could be anything. ... There is no reason why we cannot just completely erase whatever boundaries that currently exist on the definition of marriage and say it is a free-for-all, anything goes."

Another slippery slope. Permitting homosexuals to legally marry is unlikely to result in, e.g., laws permitting an adult to marry a sheep, etc.

7. Fallacy of Equivocation

An ambiguous expression is a word or phrase that has more than one distinct meaning in the context in which it is used. For instance, if I say "I went to the bank", given the context, it may be unclear whether I went to First National or the shore of the Mississippi. A fallacy of equivocation occurs when the persuasive force of an argument depends on the shifting meaning of an ambiguous expression. Here are some examples:

(Example 1)
P1 There are laws of nature.
P2 Laws must be made by a lawgiver.
C Therefore, a cosmic lawgiver (God) exists.

Here, the ambiguous expression is 'laws'. On the one hand, there are laws which form part of a legal system, and these laws require a lawgiver (a person or group of persons with the authority to create and establish government laws). On the other hand, we have what we call laws of nature, which are simply observed regularities in the way the universe operates. The latter, however, obviously need not be the results of a legislative body. Other examples of the fallacy, however, are more subtle:

(Example 2) Representative Largent of Oklahoma, arguing in Congress on July 11, 1996 in favor of the "Defense of Marriage Act", a bill stipulating that 'marriage' be between a man and a woman only, excluding homosexual marriages: "Let me just say first of all that this is not about equal rights. We have equal rights. Homosexuals have the same rights as I do. They have the ability to marry right now, today. However, when they get married, they must marry a person of the opposite sex, the same as me."

Here, the ambiguity occurs in the phrase 'equal rights'. The equal rights those who advocate homosexual marriages have in mind is the right to legally marry someone to whom you wish to make a public and life-long commitment. The "equal rights" Largent speaks of is the right to legally marry someone of the opposite gender. But guaranteeing the latter right is obviously not the same thing as guaranteeing the former right.

(Example 3)
"The pro-abortion-rights people, of course, say a baby is not a human until it is born. What do they think it is? A vegetable or a fruit? It just shows where our society is headed when we no longer have value for human life."
 - letter to the editor, Columbus Dispatch, March 10, 1996.

The ambiguous word here is 'human'. The pro-abortion-rights people say that a baby is not human in the sense that it lacks a right to life, i.e., they define the word 'human' in this context as meaning "having a right to life". The author of the passage then switches from that definition of 'human' to the definition of 'human' in the sense of having a human genetic code. It's in this sense that it is obvious that a human baby is not a vegetable or a fruit. But having a human genetic code is not the same thing as having a right to life. Corpses, for instance, have a human genetic code, but they hardly have a right to life!

8. Appeal to Popularity

The appeal to popularity occurs when people infer that something is good or true because it is popular.

(Example 1)
It's OK to cheat if everybody else does.

But merely because something is popular doesn't make it right or correct. At one time, the belief that the earth is flat was popular, but it was certainly never correct! And killing Jews may have been popular among the Nazis, but that won't make it right!

9. Appeal to Tradition

In appeals to tradition someone argues that something is good or correct because it is traditional. The problem is that merely because something is traditional is no reason to believe that it is good or right. For instance, slavery was at one time traditional in many cultures, but that's obviously not sufficient to make it right.

(Example 1)
"I believe that same-sex couples should be entitled to the legal rights that married couples enjoy.... But, my friend, that is as far as I want to go. I define marriage as a union between a man and a woman. Before you gay-rights folks land on me with both feet, I would like to remind you that I have been supportive of your movement for many years, have withstood a great deal of criticism in the process and have risked the wrath of some editors and publishers. I cannot support same-sex marriage, however, because it flies in the face of cultural and traditional family life as we have known it for centuries. And that's where I must draw the line. Sorry." - Ann Landers, The Columbus Dispatch, July 21, 1996.

Here, Ann Landers makes an explicit appeal to tradition to support her view that same-sex marriages should not be permitted. She also commits the fallacy of appeal to emotion by trying to garner sympathy for herself and the risks she has taken supporting homosexual causes in the past in order to deflect criticism of her view that same-sex marriages should not be permitted.

There are many different kinds of fallacies that people make, but the above nine types of fallacy seem to be the most common ones we make when discussing controversial issues. It's helpful to review a list of fallacies like this on a regular basis, because we all, at one time or another, tend to invoke or fall for these fallacies. But it's important to keep in mind that, as fallacies these arguments are hopelessly flawed and prove nothing about the issues which they purport to address.