4. Fallacies


A. Introducing Fallacies

            As we saw at the beginning of this tutorial, there are three types of arguments – deductive arguments, inductive arguments, and fallacies. ‘Fallacy’ is a pejorative or negative term: A fallacy is a bad argument that appears to be a good argument. This third type of argument overlaps with the first two varieties, since fallacies are flawed deductive or inductive arguments. However, not all flawed deductive or inductive arguments are fallacies: We are frequently fooled by fallacies, mistaking them for good arguments. Some bad arguments are so obviously flawed that they would never fool anyone. Here’s an example we’ve seen before:


1. The grass is green.

2. The sky is blue.

3. Therefore, God exists.


It’s clear that this is a bad argument since the premises have nothing to do with the conclusion. In contrast, fallacies are very effective at fooling people and are widely used in advertising and politics. Although they are logically deficient, fallacies are psychologically persuasive: They are used to trick an audience into accepting a conclusion without providing adequate support for it. Sometimes fallacies are used intentionally, though sometimes the author doesn’t know any better since the author doesn’t realize that the argument they have employed is flawed. Although to the untrained eye they look like good arguments, an educated person should be able to identify fallacies, to avoid being deceived by them and inadvertently using them.

            As we’ve seen, fallacies are bad arguments that appear to be good arguments. This means that if we want to understand why a particular type of argument is a fallacy we need to consider not only (1) how the argument is flawed, but also (2) how the argument deceives us. It turns out that there are two types of deception. Some fallacies deceive us by manipulating our passions – by triggering our desires or emotions so strongly that they drown out our rationality. One type of fallacy that does this is appeal to emotion, which occurs whenever someone tries to get you to do something or believe something by manipulating your emotions instead of presenting logically relevant reasons. It should be obvious why the argument is flawed – it fails to provide logically relevant reasons.  There are as many different forms of this fallacy as there are emotions: For instance, someone might appeal to your sense of pity (e.g., ‘Please give me a better grade – I lost my job last week’), your sense of vanity (e.g., ‘You should buy this car – you know you’re very attractive’), or the feeling of fear (e.g., ‘If you don’t change your political beliefs, I’m going to harm you’). You’ve probably realized that appeal to emotion is a very common fallacy. If you think you’ve encountered this fallacy, identify the particular emotion being manipulated in order to insure you’re not mistaken.

            The second variety of deception found in fallacies is sleight of hand. Sleight of hand is a method for generating false appearances. For example, magicians’ tricks often misdirect the audiences’ attention away from an action the magician doesn’t want them to notice. Similarly, shell game operators try to keep the victim’s focus on the shell under which the pea was originally placed as they surreptitiously move it under a different shell. In fallacies, sleight of hand exploits our cognitive weaknesses or laziness, and is used to get us to confuse one thing with another. We’ve already seen some examples of these types of fallacies: For instance, we saw that equivocation – a word or phrase with multiple meanings – can be used to hide a gap in an argument. We also saw that cherry picking presents a biased sample as an unbiased one. And we saw that the joint effect argument presents one thing as the cause of another when in fact they are both effects of another cause. An example of the sleight of hand fallacy that we haven’t seen yet is the ad hominem or ‘against the person’ fallacy.[1] This argument is used to undermine an opponent’s argument or claim, and it does this by attacking the opponent’s character, motives, or conduct. For example, ‘The previous speaker is a drug abuser, so you should disregard his criticisms of the safety record at the nuclear plant.’ Other versions of the ad hominem fallacy suggest that the opponent is biased or claim that the she is a hypocrite, i.e., that she doesn’t practice what she preaches. (Keep in mind that these criticisms are often exaggerated or false.) Ad hominem arguments are frequently used in political debates. Why is an ad hominem argument a fallacy? The argument is flawed, since it misses the intended target: The opponent’s character, motives, or conduct and the opponent’s claim or argument are two different things. Attacking the first has no impact the second: A person who is biased or has done bad things is still able to make true claims or construct successful arguments. The same is true for hypocrites: Alcoholics have first-hand experience with the harmful effects of substance abuse, and their warnings about alcohol abuse aren’t any less valid if they continue drinking.[2] How does an ad hominem argument use sleight of hand to deceive us? To the untrained eye it seems like the argument hits the right target. In other words, one confuses the claim or argument being criticized with the reputation of the person making the claim or argument, even though they are very different things.

            Let’s consider some other examples of fallacies and try to figure out the flaw in each argument and the form of deception they employ. Another common fallacy is the appeal to popularity, which asserts that you should do something or believe something because it is popular. This fallacy is used frequently in advertising. For example, the McDonald’s sign states “Over 99 billion served” as a reason for you to eat there.


Peer pressure is another example of the appeal to popularity fallacy. Why is this a bad argument? A belief or practice can be popular without there being any reasons supporting it. History is full of examples of large groups of people believing things that are false or doing things that are immoral or stupid. In addition, if something is a good idea for most people, it might not be a good idea for you. For example, if you’re a diabetic, items that are healthy for other people to eat may be harmful to you. But why is this flawed argument so psychologically persuasive? In other words, what type of deception does it use? It manipulates our passions. Which type of passion? Our desire to fit in and be accepted. We are social beings and we want other people to have a positive impression of us. Appeal to popularity exploits this desire to get us to accept a claim without providing any logical support for it.[3]

            Composition and division are a pair of fallacies that are the mirror image of each other, arguing, respectively, from the parts to the whole, and from the whole to the parts. Composition is the claim that a property found in the parts is also found in the whole. For example, since all the players on the team are excellent, the team as a whole must be excellent. Division works in the opposite direction, arguing that a property which is found in the whole is also found in the parts. Reversing the previous example: Since the team is excellent, all the players on the team must be excellent. The names should help you distinguish these two fallacies: Composition takes parts and combines them together into a whole, and division takes a whole and separates it into individual parts. In other words, composition refers to parts in the premises and the whole in the conclusion, and division does the reverse. It should be apparent why these are bad arguments: A team might have excellent players who don’t play very well together, and an excellent team may have average players who happen to work together and complement each other very well. The parts and the whole are two distinct spheres and a property found in one might not be found in the other. Why do these fallacies fool us and what type of deception do they use? They use sleight of hand: To the untrained eye, the parts and the whole seem to be the same thing. So it seems that the premise and the conclusion are talking about the same thing when in fact they aren’t.

            Another common fallacy, used frequently in advertisements and political endorsements, is appeal to unqualified authority. This fallacy uses the testimony of someone who is presented as an expert in a particular area when in fact they aren’t. As we’ll see in the final chapter, experts are an important source of knowledge. But some people take advantage of this by trying to give the give the impression that someone has expertise when in fact they don’t. The flaw in this argument should be obvious. What type of deception does it use? Manipulating our passions? Sleight of hand? Actually, it uses both of them, or to be more precise, there are two types of appeal to unqualified authority and each uses a different type of deception. The first type is irrelevant expertise, which occurs when the supposed authority is in fact an expert but not in the area in question. For example, advertisements for supplements and health care products sometimes use testimony from people identified as doctors whose doctorates are in fact in areas like English literature or political science instead of medicine or nutrition! This variety of appeal to unqualified authority uses sleight of hand to deceive us, for it tries to get us to confuse irrelevant expertise with relevant expertise. The second variety of appeal to unqualified authority consists in celebrity endorsements, where a famous person, e.g., an athlete, musician, or actor, endorses something, e.g., a product, political candidate, or belief. The celebrity almost always lacks expertise in the relevant area. This version of the fallacy deceives us by manipulating our passions, in this case the fact that celebrities are people we identify with and look up to. In the United States, we have an unhealthy obsession with celebrity: We want to be like them – to be successful, appreciated by others, wealthy, sexy, etc., and irrationally believe that if we use the same products as the celebrity, vote for the same candidate, hold the same beliefs, etc., that it will somehow give us the desired traits of the celebrity who is being mimicked. That’s why this version of the fallacy is so psychologically persuasive. Advertisers and political campaigners use this technique in order to take advantage of our emotional insecurities and irrational beliefs.


B. Fallacies continued

            Appeal to ignorance is a fallacy which asserts that the lack of evidence for a claim being true is evidence that it is false, or conversely that the lack of evidence that a claim is false is proof that it is true. For example, “Since my opponents can’t prove that the painting was produced in 1640, it must not have been.” And, “Skeptics can’t prove that my incantation didn’t cause the rainfall, so my incantation must have been the cause.” Why is appeal to ignorance a bad argument? It assumes that you must either affirm or deny a particular claim, and overlooks a third and better alternative – withholding judgment until adequate evidence is available. In other words, it treats the lack of evidence as evidence for something else when in fact it isn’t evidence of anything. Another sign that appeal to ignorance is a fallacy is that it could be used to support both of the opposing positions, which would produce a contradiction. The legal principle of ‘Innocent until proven guilty’ is relevant here: In criminal trials, we place the burden of proof on the prosecution because it may be impossible for an innocent defendant to prove their innocence, namely, if they can’t find sufficient evidence, e.g., a solid alibi. However, the fact that a defendant is found not guilty doesn’t prove their innocence, for someone can be guilty without there being sufficient evidence of their guilt. Arguing that the lack of evidence of guilt proves one’s innocence is an instance of appeal to ignorance. What type of deception does this fallacy use? Sleight of hand: Lack of evidence is easily confused with evidence for the contrary claim, though they are in fact two very different things.

            Another common fallacy is the straw man argument, which is commonly used in debates, especially political ones. Instead of attacking the view of one’s opponent, the fallacy attacks a simplistic misrepresentation of this view. For example, “Supporters of the proposed subway aren’t concerned about our current budget deficits.” And, “Opponents of the death penalty want more innocent children to be brutally killed.” In fact, the supporters of the subway project might want to eliminate the budget deficits by raising taxes or by making cuts elsewhere, or may think that the subway project will pay for itself. And opponents of capital punishment argue that life imprisonment deters criminals as much as the death penalty does. As the name ‘straw man’ suggests, the actual opponent is replaced with a cheap replica that is much easier to knock over. The flaw in the argument should be apparent: It isn’t attacking the right target. As you probably guessed, the straw man fallacy uses sleight of hand to deceive us: To the untrained eye, the simplistic misrepresentation is indistinguishable from the opponent’s actual view. If someone ascribes an absurd or ridiculous view to their opponent, this should arouse the suspicion that they are using a straw man argument.[4]

            Slippery slope is another fallacy commonly used in political debates. This fallacy claims that one seemingly innocuous event will generate an increasingly harmful chain of events. It is also referred to as ‘the snowball effect’. Here’s an example: “If mercy killing is allowed, our respect for the lives of the elderly, sick and poor will be eroded. We will find it easier to kill them instead of paying for their health care. Eventually we will lose respect for all human life, and will start killing each other for the most petty reasons.” Why is this a fallacy? Because the chain of causes and effects is unlikely: For example, allowing terminally ill people who are enduring a great deal of suffering to end their lives is unlikely to lead to an erosion of our respect for life because, arguably, it is motivated by respect, i.e., respect for the quality of life of terminal patients and their ability to control their own destiny. Whenever you hear a claim that something will lead to disastrous results, you should carefully consider how likely it actually is that the first thing will lead to the second. If the sequence of events is likely, then it is a good argument, but if the sequence is unlikely, it is a slippery slope fallacy. This fallacy deceives us by using sleight of hand: We become distracted by the disastrous effects that are being predicted, and fail to consider how likely they are. Also, we tend to be impressed by claims about long chains of causes and effects since we are inclined to identify patterns in the world, even where there aren’t any. But in fact, the longer the chain of causes and effects, the weaker it is because it makes it more likely that something will obstruct or interfere with the sequence of events.

            The last fallacy we’ll discuss is begging the question. This fallacy uses the conclusion as a premise for itself or for one of its supporting arguments. It is also known as a ‘circular argument’ or a ‘vicious circle’. Here are a couple of examples:


1. No cars are bikes.                          

2. Therefore, no bikes are cars.


1. The authors of the Bible were divinely inspired by God.

2. Therefore, the Bible is true.

3. The Bible says that God exists.

4. Therefore, God exists.


In the first example, the premise is merely a modified version of the conclusion. Begging the question rarely uses an unmodified version, since that would be too obvious. In the second example, the final conclusion (4) is assumed in the initial premise (1): If God inspired the authors of the Bible then God must exist. Why is begging the question a flawed argument? Because it doesn’t provide any support for the conclusion: A conclusion can’t support itself. In effect, the author is merely assuming that the conclusion is true, or ‘begging the question’. What type of deception does it use? Sleight of hand: The premise in question is usually a modified form of the conclusion or implicitly assumes the conclusion, and is often separated from the conclusion by other lines in the argument, as illustrated by the examples above. Consequently, it seems like the premise provides independent support for the conclusion when in fact it doesn’t.

            There are many more fallacies. If you’re interested in learning about them or want to see more examples of the fallacies discussed above, check out the links I’ve posted here.


[1] Many fallacies have Latin names, but only a few of these names – like ad hominem and post hoc – are used more commonly by English speakers than their English translations.

[2] However, when someone has an established reputation for lying, we have good reason to to doubt the truthfulness of their testimony. This is why a person who perjures themselves in court is excluded from serving as a witness.

[3] Be careful not to confuse the appeal to popularity fallacy with the abductive criterion of conservatism: Conservatism is the idea that, all things being equal, something that is consistent with what we already believe is more likely to be true than something that isn’t. Unlike the appeal to popularity, conservatism doesn’t try to get us to accept a claim because that’s what other people happen to believe.

[4] The straw man and ad hominem fallacies are often mixed up, so make sure you’re able to clearly distinguish them: The ad hominem fallacy attacks the person making a claim, whereas the straw man fallacy misrepresents the position that a person is taking.