A fallacy is a kind of error in reasoning. The list of fallacies contains 209 names of the most common fallacies, and it provides brief explanations and examples of each of them. Fallacies should not be persuasive, but they often are. Fallacies may be created unintentionally, or they may be created intentionally in order to deceive other people. The vast majority of the commonly identified fallacies involve arguments, although some involve explanations, or definitions, or other products of reasoning. Sometimes the term "fallacy" is used even more broadly to indicate any false belief or cause of a false belief. The list below includes some fallacies of these sorts, but most are fallacies that involve kinds of errors made while arguing informally in natural language.
An informal fallacy is fallacious because of both its form and its content. The formal fallacies are fallacious only because of their logical form. For example, the slippery slope fallacy has this form: Step 1 "leads to" step 2. Step 2 leads to step 3. Step 3 leads to. until we reach an obviously unacceptable step, so step 1 is not acceptable. That form occurs in both good arguments and fallacious arguments. The quality of an argument of this form depends crucially on the probabilities that each step does lead to the next, but the probabilities involve the argument's content, not merely its form.
The discussion that precedes the long alphabetical list of fallacies begins with an account of the ways in which the term "fallacy" is vague. Attention then turns to the number of competing and overlapping ways to classify fallacies of argumentation. For pedagogical purposes, researchers in the field of fallacies disagree about the following topics: which name of a fallacy is more helpful to students' understanding; whether some fallacies should be de-emphasized in favor of others; and which is the best taxonomy of the fallacies. Researchers in the field are also deeply divided about how to define the term "fallacy" itself, how to define certain fallacies, and whether any theory of fallacies at all should be pursued if that theory's goal is to provide necessary and sufficient conditions for distinguishing between fallacious and non-fallacious reasoning generally. Analogously, there is doubt in the field of ethics regarding whether researchers should pursue the goal of providing necessary and sufficient conditions for distinguishing moral actions from immoral ones.
Table of Contents
The first known systematic study of fallacies was due to Aristotle in his De Sophisticis Elenchis (Sophistical Refutations), an appendix to the Topics. He listed thirteen types. After the Dark Ages, fallacies were again studied systematically in Medieval Europe. This is why so many fallacies have Latin names. The third major period of study of the fallacies began in the later twentieth century due to renewed interest from the disciplines of philosophy, logic, communication studies, rhetoric, psychology, and artificial intelligence.
The more frequent the error within public discussion and debate the more likely it is to have a name. That is one reason why there is no specific name for the fallacy of subtracting five from thirteen and concluding that the answer is seven, though the error is common.
The term "fallacy" is not a precise term. One reason is that it is ambiguous. It can refer either to (a) a kind of error in an argument, (b) a kind of error in reasoning (including arguments, definitions, explanations, and so forth), (c) a false belief, or (d) the cause of any of the previous errors including what are normally referred to as "rhetorical techniques." Philosophers who are researchers in fallacy theory prefer to emphasize (a), but their lead is often not followed in textbooks and public discussion.
Regarding (d), ill health, being a bigot, being hungry, being stupid, and being hypercritical of our enemies are all sources of error in reasoning, so they could qualify as fallacies of kind (d), but they are not included in the list below. On the other hand, wishful thinking, stereotyping, being superstitious, rationalizing, and having a poor sense of proportion are sources of error and are included in the list below, though they wouldn't be included in a list devoted only to faulty arguments. Thus there is a certain arbitrariness to what appears in lists such as this. What have been left off the list below are the following persuasive techniques commonly used to influence others and to cause errors in reasoning: apple polishing, assigning the burden of proof inappropriately, using propaganda techniques, ridiculing, being sarcastic, selecting terms with strong negative or positive associations, using innuendo, and weasling. All of the techniques are worth knowing about if one wants to reason well.
In describing the fallacies below, the custom is followed of not distinguishing between a reasoner using a fallacy and the reasoning itself containing the fallacy.
Real arguments are often embedded within a very long discussion. Richard Whately, one of the greatest of the 19th century researchers into informal logic, wisely said, "A very long discussion is one of the most effective veils of Fallacy;. a Fallacy, which when stated barely. would not deceive a child, may deceive half the world if diluted in a quarto volume."
2. Taxonomy of Fallacies
There are a number of competing and overlapping ways to classify fallacies of argumentation. For example, they can be classified as either formal or informal. A formal fallacy can be detected by examining the logical form of the reasoning, whereas an informal fallacy depends upon the content of the reasoning and possibly the purpose of the reasoning. That is, informal fallacies are errors of reasoning that cannot easily be expressed in our system of formal logic (such as symbolic, deductive, predicate logic). The list below contains very few formal fallacies. Fallacious arguments also can be classified as deductive or inductive, depending upon whether the fallacious argument is most properly assessed by deductive standards or instead by inductive standards. Deductive standards demand deductive validity. but inductive standards require inductive strength such as making the conclusion more likely. Fallacies can be divided into categories according to the psychological factors that lead people to use them, and they can also be divided into categories according to the epistemological or logical factors that cause the error. In the latter division there are three categories: (1) the reasoning is invalid but is presented as if it were a valid argument, or else it is inductively much weaker than it is presented as being, (2) the argument has an unjustified premise, or (3) some relevant evidence has been ignored or suppressed. Regarding (2), a premise can be justified or warranted at a time even if we later learn that the premise was false, and it can be justified if we are reasoning about what would have happened even when we know it didn't happen.
Similar fallacies are often grouped together under a common name intended to bring out how the fallacies are similar. Here are three examples. Fallacies of relevance include fallacies that occur due to reliance on an irrelevant reason. In addition, ad hominem. appeal to pity. and affirming the consequent are some other fallacies of relevance. Accent. amphiboly and equivocation are examples of fallacies of ambiguity. The fallacies of illegitimate presumption include begging the question. false dilemma. no true Scotsman. complex question and suppressed evidence. Notice how these categories don't fall neatly into just one of the categories (1), (2), and (3) above.
It is commonly claimed that giving a fallacy a name and studying it will help the student identify the fallacy in the future and will steer them away from using the fallacy in their own reasoning. As Steven Pinker says in The Stuff of Thought (p. 129),
If a language provides a label for a complex concept, that could make it easier to think about the concept, because the mind can handle it as a single package when juggling a set of ideas, rather than having to keep each of its components in the air separately. It can also give a concept an additional label in long-term memory, making it more easily retrivable than ineffable concepts or those with more roundabout verbal descriptions.
For pedagogical purposes, researchers in the field of fallacies disagree about the following topics: which name of
a fallacy is more helpful to students' understanding; whether some fallacies should be de-emphasized in favor of others; and which is the best taxonomy of the fallacies. Fallacy theory is criticized by some teachers of informal reasoning for its over-emphasis on poor reasoning rather than good reasoning. Do colleges teach the Calculus by emphasizing all the ways one can make mathematical mistakes? The critics want more emphasis on the forms of good arguments and on the implicit rules that govern proper discussion designed to resolve a difference of opinion. But there has been little systematic study of which emphasis is more successful.
4. What is a fallacy?
Researchers disagree about how to define the very term "fallacy." Focusing just on fallacies in sense (a) above, namely fallacies of argumentation, some researchers define a fallacy as an argument that is deductively invalid or that has very little inductive strength. Because examples of false dilemma. inconsistent premises, and begging the question are valid arguments in this sense, this definition misses some standard fallacies. Other researchers say a fallacy is a mistake in an argument that arises from something other than merely false premises. But the false dilemma fallacy is due to false premises. Still other researchers define a fallacy as an argument that is not good. Good arguments are then defined as those that are deductively valid or inductively strong, and that contain only true, well-established premises, but are not question-begging. A complaint with this definition is that its requirement of truth would improperly lead to calling too much scientific reasoning fallacious; every time a new scientific discovery caused scientists to label a previously well-established claim as false, all the scientists who used that claim as a premise would become fallacious reasoners. This consequence of the definition is acceptable to some researchers but not to others. Because informal reasoning regularly deals with hypothetical reasoning and with premises for which there is great disagreement about whether they are true or false, many researchers would relax the requirement that every premise must be true. One widely accepted definition defines a fallacious argument as one that either is deductively invalid or is inductively very weak or contains an unjustified premise or that ignores relevant evidence that is available and that should be known by the arguer. Finally, yet another theory of fallacy says a fallacy is a failure to provide adequate proof for a belief, the failure being disguised to make the proof look adequate.
Other researchers recommend characterizing a fallacy as a violation of the norms of good reasoning, the rules of critical discussion, dispute resolution, and adequate communication. The difficulty with this approach is that there is so much disagreement about how to characterize these norms.
In addition, all the above definitions are often augmented with some remark to the effect that the fallacies are likely to persuade many reasoners. It is notoriously difficult to be very precise about this vague and subjective notion of being likely to persuade, and some researchers in fallacy theory have therefore recommended dropping the notion in favor of "can be used to persuade."
Some researchers complain that all the above definitions of fallacy are too broad and do not distinguish between mere blunders and actual fallacies, the more serious errors.
Researchers in the field are deeply divided, not only about how to define the term "fallacy" and how to define some of the individual fallacies, but also about whether any general theory of fallacies at all should be pursued if that theory's goal is to provide necessary and sufficient conditions for distinguishing between fallacious and non-fallacious reasoning generally. Analogously, there is doubt in the field of ethics whether researchers should pursue the goal of providing necessary and sufficient conditions for distinguishing moral actions from immoral ones.
5. Other Controversies
How do we defend the claim that an item of reasoning should be labeled as a particular fallacy? A major goal in the field of informal logic is provide some criteria for each fallacy. Schwartz presents the challenge this way:
Fallacy labels have their use. But fallacy-label texts tend not to provide useful criteria for applying the labels. Take the so-called ad verecundiam fallacy, the fallacious appeal to authority. Just when is it committed? Some appeals to authority are fallacious; most are not. A fallacious one meets the following condition: The expertise of the putative authority, or the relevance of that expertise to the point at issue, are in question. But the hard work comes in judging and showing that this condition holds, and that is where the fallacy-label texts leave off. Or rather, when a text goes further, stating clear, precise, broadly applicable criteria for applying fallacy labels, it provides a critical instrument more fundamental than a taxonomy of fallacies and hence to that extent goes beyond the fallacy-label approach. The further it goes in this direction, the less it need to emphasize or event to use fallacy labels. (Schwartz, 232)
The controversy here is the extent to which it is better to teach students what Schwartz calls "the critical instrument" than to teach the fallacy-label approach. Is the fallacy-label approach better for some kinds of fallacies than others? If so, which others?
Another controversy involves the relationship between the fields of logic and rhetoric. In the field of rhetoric, the primary goal is to persuade the audience. The audience is not going to be persuaded by an otherwise good argument with true premises unless they believe those premises are true. Philosophers tend to de-emphasize this difference between rhetoric and informal logic, and they concentrate on arguments that should fail to convince the ideally rational reasoner rather than on arguments that are likely not to convince audiences who hold certain background beliefs. Given specific pedagogical goals, how pedagogically effective is this de-emphasis?
Advertising in magazines and on television is designed to achieve visual persuasion. And a hug or the fanning of fumes from freshly baked donuts out onto the sidewalk are occasionally used for visceral persuasion. There is some controversy among researchers in informal logic as to whether the reasoning involved in this nonverbal persuasion can always be assessed properly by the same standards that are used for verbal reasoning.
6. Partial List of Fallacies
Consulting the list below will give a general idea of the kind of error involved in passages to which the fallacy name is applied. However, simply applying the fallacy name to a passage cannot substitute for a detailed examination of the passage and its context or circumstances because there are many instances of reasoning to which a fallacy name might seem to apply, yet, on further examination, it is found that in these circumstances the reasoning is really not fallacious.
Abusive Ad Hominem
The accent fallacy is a fallacy of ambiguity due to the different ways a word is emphasized or accented.
A member of Congress is asked by a reporter if she is in favor of the President's new missile defense system, and she responds, "I'm in favor of a missile defense system that effectively defends America."
With an emphasis on the word "favor," her response is likely to favor the President's missile defense system. With an emphasis, instead, on the words "effectively defends," her remark is likely to be against the President's missile defense system. And by using neither emphasis, she can later claim that her response was on either side of the issue. Aristotle's version of the fallacy of accent allowed only a shift in which syllable is accented within a word.
We often arrive at a generalization but don't or can't list all the exceptions. When we reason with the generalization as if it has no exceptions, our reasoning contains the fallacy of accident. This fallacy is sometimes called the "fallacy of sweeping generalization."
People should keep their promises, right? I loaned Dwayne my knife, and he said he'd return it. Now he is refusing to give it back, but I need it right now to slash up my neighbors who disrespected me.
People should keep their promises, but there are exceptions to this generaliztion as in this case of the psychopath who wants Dwayne to keep his promise to return the knife.