Logical Fallacies

Attacking the Person/Ad Hominem

Attacking the Person/ Ad Hominem Definition: The person presenting an argument is attacked instead of the argument itself. This takes many forms. For example, the person's character, nationality or religion may be attacked. Alternatively, it may be pointed out that a person stands to gain from a favourable outcome. Or, finally, a person may be attacked by association, or by the company he keeps. There are three major forms of Attacking the Person: 1.ad hominem (abusive): instead of attacking an assertion, the argument attacks the person who made the assertion. 2.ad hominem (circumstantial): instead of attacking an assertion the author points to the relationship between the person making the assertion and the person's circumstances. 3.ad hominem (tu quoque): this form of attack on the person notes that a person does not practise what he preaches. Examples: i.You may argue that God doesn't exist, but you are just following a fad. (ad hominem abusive) ii.We should discount what Premier Klein says about taxation because he won't be hurt by the increase. (ad hominem circumstantial) iii.We should disregard Share B.C.'s argument because they are being funded by the logging industry. (ad hominem circumstantial) iv.You say I shouldn't drink, but you haven't been sober for more than a year. (ad hominem tu quoque) Proof: Identify the attack and show that the character or circumstances of the person has nothing to do with the truth or falsity of the proposition being defended.

Begging the Question

Begging the Question (also known as: assuming the initial point, assuming the answer, chicken and the egg argument, circulus in probando, circular reasoning [form of], vicious circle) Description: Any form of argument where the conclusion is assumed in one of the premises. Many people use the phrase "begging the question" incorrectly when they use it to mean, "prompts one to ask the question". That is NOT the correct usage. Begging the question is a form of circular reasoning. Logical Forms: Claim X assumes X is true. Therefore, claim X is true. Example #1: Paranormal activity is real because I have experienced what can only be described as paranormal activity. Explanation: The claim, "paranormal activity is real" is supported by the premise, "I have experienced what can only be described as paranormal activity." The premise presupposes, or assumes, that the claim, "paranormal activity is real" is already true. Example #2: The reason everyone wants the new "Slap Me Silly Elmo" doll is because this is the hottest toy of the season! Explanation: Everyone wanting the toy is the same thing as it being "hot," so the reason given is no reason at all—it is simply rewording the claim and trying to pass it off as support for the claim. Exception: Some assumptions that are universally accepted could pass as not being fallacious. People like to eat because we are biologically influenced to eat.

Biased/Unrepresentative Sample

Biased/Unrepresentative Sample (also known as: biased statistics, loaded sample, prejudiced statistics, prejudiced sample, loaded statistics, biased induction, biased generalization, unrepresentative sample, unrepresentative generalization) Description: Drawing a conclusion about a population based on a sample that is biased, or chosen in order to make it appear the population on average is different than it actually is. This differs from the hasty generalization fallacy, where the biased sample is specifically chosen from a select group, and the small sample is just a random sample, but too small to get any accurate information. Logical Form: Sample S, which is biased, is taken from population P. Conclusion C is drawn about population P based on S. Example #1: Based on a survey of 1000 American homeowners, 99% of those surveyed have two or more automobiles worth on average $100,000 each. Therefore, Americans are very wealthy. Explanation: Where did these homeowners live? Beverly Hills, CA. If the same exact survey was taken in Detroit, the results would be quite different. It is fallacious to accept the conclusion about the American population in general based on not just the geographical sample, but also the fact that homeowners were only surveyed. Example #2: Pastor Pete: People are turning to God everywhere! 9 out of 10 people I interviewed said that they had a personal relationship with Jesus Christ. Fred: Where did you find these people you interviewed? Pastor Pete: In my church. Explanation: Pastor Pete has drawn a conclusion about religious beliefs from people "everywhere" based on people he has interviewed in his church. That's like concluding that the world likes to dance naked in front of strangers after interviewing a group of strippers. Exception: What exactly is "biased" is subjective, but some biases are very clear. Tip: Be very wary of statistics. Look at the source and details of the studies which produced the statistics. Very often you will find some kind of bias.

False Dilemma

False Dilemma - (also known as: false dichotomy*, the either-or fallacy, either-or reasoning, fallacy of false choice, fallacy of false alternatives, black-and-white thinking, the fallacy of exhaustive hypotheses, bifurcation, excluded middle, no middle ground, polarization) Description: When only two choices are presented yet more exist, or a spectrum of possible choices exists between two extremes. False dilemmas are usually characterized by "either this or that" language, but can also be characterized by omissions of choices. Another variety is the false trilemma, which is when three choices are presented when more exist. Logical Form: Either X or Y is true. Either X, Y, or Z is true. Example (two choices): You are either with God, or against him. Explanation: As Obi Wan Kenobi so eloquently puts it in Star Wars episode III, "Only a Sith deals in absolutes!" There are also those who simply don't believe there is a God to be either with or against. Example (omission): I thought you were a good person, but you weren't at church today. Explanation: The assumption here is that bad people don't go to church. Of course, good people exist who don't go to church, and good church-going people could have had a really good reason not to be in church -- like a hangover from the swingers' gathering the night before. Exception: There may be cases when the number of options really is limited. For example, if an ice cream man just has chocolate and vanilla left, it would be a waste of time insisting he has mint chocolate chip. It is also not a fallacy if other options exist, but you are not offering other options as a possibility. For example: Mom: Billy, it's time for bed. Billy: Can I stay up and watch a movie? Mom: You can either go to bed or stay up for another 30 minutes and read. Billy: That is a false dilemma! Mom: No, it's not. Here, read Bo's book and you will see why. Billy: This is freaky, our exact conversation is used as an example in this book! Tip: Be conscious of how many times you are presented with false dilemmas, and how many times you present yourself with false dilemmas. * Staying true to the definitions, the false dilemma is different from the false dichotomy in that a dilemma implies two equally unattractive options whereas a dichotomy generally comprises two opposites. This is a fine point, however, and is generally ignored in common usage.

Non Sequitur

Non Sequitur (also known as: derailment, "that does not follow", irrelevant reason, invalid inference, non-support, argument by scenario [form of], false premise [form of], questionable premise [form of]) Description: When the conclusion does not follow from the premises. In more informal reasoning, it can be when what is presented as evidence or reason is irrelevant or adds very little support to the conclusion. Logical Form: Claim A is made. Evidence is presented for Claim A. Therefore, claim C is true. Example #1: People generally like to walk on the beach. Beaches have sand. Therefore, having sand floors in homes would be a great idea! Explanation: As cool as the idea of sand floors might sound, the conclusion does not follow from the premises. The fact that people generally like to walk on sand does not mean that they want sand in their homes, just like because people generally like to swim, they shouldn't flood their houses. Example #2: Buddy Burger has the greatest food in town. Buddy Burger was voted #1 by the local paper. Therefore, Phil, the owner of Buddy Burger, should run for President of the United States. Explanation: I bet Phil makes one heck of a burger, but it does not follow that he should be President. Exception: There really is no exceptions to this rule. Any good argument must have a conclusion that follows from the premises. Tip: One of the best ways to expose non sequiturs is by constructing a valid analogy that exposes the absurdity in the argument. Variations: There are many forms of non sequiturs including argument by scenario, where an irrelevant scenario is given in an attempt to support the conclusion. Other forms use different rhetorical devices that are irrelevant to the conclusion.

Ad Populum Popularity/Bandwagon

Popularity/Bandwagon (also known as: bandwagon argument, peer pressure) Description: Using the popularity of a premise or proposition as evidence for its truthfulness. This is a fallacy which is very difficult to spot because our "common sense" tells us that if something is popular, it must be good/true/valid, but this is not so, especially in a society where clever marketing, social and political weight, and money can buy popularity. Logical Form: Everybody is doing X. Therefore, X must be the right thing to do. Example #1: Mormonism is one of the fastest growing sects of Christianity today so that whole story about Joseph Smith getting the golden plates that, unfortunately, disappeared back into heaven, must be true! Explanation: Mormonism is indeed rapidly growing, but that fact does not prove the truth claims made by Mormonism in any way. Example #2: A 2005 Gallup Poll found that an estimated 25% of Americans over the age of 18 believe in astrology—or that the position of the stars and planets can affect people's lives. That is roughly 75,000,000 people. Therefore, there must be some truth to astrology! Explanation: No, the popularity of the belief in astrology is not related to the truthfulness of astrological claims. Beliefs are often cultural memes that get passed on from person to person based on many factors other than truth. Exception: When the claim being made is about the popularity or some related attribute that is a direct result of its popularity. People seem to love the movie, The Shawshank Redemption. In fact, it is currently ranked #1 at IMDB.com, based on viewer ratings. Tip: Avoid this fallacy like you avoid a kiss from your great aunt with the big cold sore on her lip. Variation: The bandwagon effect is a related cognitive bias that demonstrates people tend to believe and do things because many other people do, as well. This is also referred to as "herd behavior" and "groupthink".

Slippery Slope

Slippery Slope- also known as absurd extrapolation, thin edge of the wedge, camel's nose, domino fallacy) Definition: When a relatively insignificant first event is suggested to lead to a more significant event, which in turn leads to a more significant event, and so on, until some ultimate, significant event is reached, where the connection of each event is not only unwarranted, but with each step it becomes more and more improbable. Many events are usually present in this fallacy, but only two are actually required -- usually connected by "the next thing you know..." Logical Form: If A, then B, then C, ... then ultimately Z! Example #1: We cannot unlock our child from the closet because if we do, she will want to roam the house. If we let her roam the house, she will want to roam the neighborhood. If she roams the neighborhood, she will get picked up by a stranger in a van, who will sell her in a sex slavery ring in some other country. Therefore, we should keep her locked up in the closet. Explanation: In this example, it starts out with reasonable effects to the causes. For example, yes, if the child is allowed to go free in her room, she would most likely want to roam the house -- 95% probability estimate[1]. Sure, if she roams the house, she will probably want the freedom of going outside, but not necessarily "roaming the neighborhood", but let's give that a probability of say 10%. Now we start to get very improbable. The chances of her getting picked up by a stranger (.05%) in a van (35%) to sell her into sex slavery (.07%) in another country (40%) is next to nothing when you do all the math: .95 x .10 x .0005 x .35 x .0007 x .4 = about 1 in 25,000,000. Morality and legality aside, is it really worth it to keep a child locked in a closet based on those odds?

Straw Man

Straw Man Description: Substituting a person's actual position or argument with a distorted, exaggerated, or misrepresented version of the position of the argument. Logical Form: Person 1 makes claim Y. Person 2 restates person 1's claim (in a distorted way). Person 2 attacks the distorted version of the claim. Therefore, claim Y is false. Example #1: Ted: Biological evolution is both a theory and a fact. Edwin: That is ridiculous! How can you possibly be absolutely certain that we evolved from pond scum! Ted: Actually that is a gross misrepresentation of my assertion. I never claimed we evolved from pond scum. Unlike math and logic, science is based on empirical evidence and, therefore, a scientific fact is something that is confirmed to such a degree that it would be perverse to withhold provisional consent. The empirical evidence for the fact that biological evolution does occur falls into this category. Explanation: Edwin has ignorantly mischaracterized the argument by a) assuming we evolved from pond scum (whatever that is exactly), and b) assuming "fact" means "certainty". Example #2: Zebedee: What is your view on the Christian God? Mike: I don't believe in any gods, including the Christian one. Zebedee: So you think that we are here by accident, and all this design in nature is pure chance, and the universe just created itself? Mike: You got all that from me stating that I just don't believe in any gods? Explanation: Mike made one claim: that he does not believe in any gods. From that, we can deduce a few things, like he is not a theist, he is not a practicing Christian, Catholic, Jew, or a member of any other religion that requires the belief in a god, but we cannot deduce that he believes we are all here by accident, nature is chance, and the universe created itself. Mike might have no beliefs about these things whatsoever. Perhaps he distinguishes between "accident" and natural selection, perhaps he thinks the concept of design is something we model after the universe, perhaps he has some detailed explanation based on known physics as to how the universe might have first appeared, or perhaps he believes in some other supernatural explanation. Regardless, this was a gross mischaracterization of Mike's argument. Exception: At times, an opponent might not want to expand on the implications of his or her position, so making assumptions might be the only way to get the opponent to point out that your interpretation is not accurate, then they will be forced to clarify.