Informal Fallacies

Unfortunately, even when we pay careful attention to the logical principles, our reasoning can still go awry through any of a number of informal fallacies. Like the principles of formal logic, informal fallacies usually involve a faulty relationship between an argument’s claim and its support. Familiarity with these flaws in reasoning is especially useful during the revision stage, when, with these fallacies in mind, you examine the relationship between your claim and its support. Since an inclusive list of these fallacies is a very long one—as inexhaustible as human inventiveness—included here are only those fallacies that frequently turn up in student writing. For each fallacy, the category or categories of argument in which it is most likely to occur are also indicated. 

Ad Hominem Argument 

An ad hominem argument is against the arguer (in Latin ad hominem means “to the man”) rather than against the argument: “Smith’s argument against increasing taxes on the rich is worthless because he himself is rich.” This fallacy, which substitutes irrelevant judgments of an individual for reasonable evaluations of an issue, is most likely to occur in evaluative arguments. 

Ad Populum Argument 

Ad populum is Latin for “to the people.” One commits the ad populum fallacy when supporting a claim by referring to popular opinion or behavior to justify it. A teenager trying to convince her parents to remove her curfew because “everybody else’s parents have done it” is attempting to convince her parents through an appeal to popular behavior rather than to reason. This fallacy is a corruption of the legitimate tactic of appealing to established authorities to strengthen a claim. 

Circular Argument 

A circular argument (also known as begging the question) is one in which the claim is already contained in the support: “John did not succeed on the track team [the claim] because he did not do well in track events [the support].” In this example, “did not do well in track events” really only restates “did not succeed on the track team”; it adds no new information about  why John didn’t succeed. Another common version of circular argument, or begging the question, assumes what has to be proven, as in the statement “This film should be banned because it contains immoral scenes.” This claim requires a definition of  immoral and evidence that the film meets this definition. Lacking such material, the claim begs the question of the immorality of the film. Evaluative, interpretive, and causal arguments seem to be particularly subject to this fallacy. One giveaway that your argument is circular is that your supporting statements repeat a key term from your claim. 

Distraction 

Distraction is bringing in irrelevant points to distract attention from the issue being argued: “Sure I cheated on my income taxes, but I’ve never broken any other laws.” It is also known as the red herring, from the practice of dragging a dead herring across a trail to distract hunting dogs from the scent of their prey. Distraction is frequently used to deflect unfavorable evaluations. 

Either-Or Argument 

The either-or argument is setting up two extreme positions as the only alternatives and denying any possible middle ground: “The painting is either a masterpiece or trash.” The painting could be something in between. Also known as bifurcation or the fallacy of the excluded middle, this fallacy can occur in any category of argument, though it is probably most frequent in evaluations (as in the claim about the painting) or in recommendations, where extreme solutions are sometimes seen as the only options: “Either we build a new computer facility or we give up on using computers at this school.” 

Emotive Language 

The fallacy of emotive language involves making a case through slanted, value-laden language rather than through reasonable support, as in the statement “Smelling blood, the media will attack and destroy any candidate with a newsworthy weak spot.” This claim, in its implicit identification of the media with carnivorous beasts, presumes a value judgment about the media that the claim does not justify. Writers of argument should try to refrain from using prejudicial language, at least until their claims have been reasonably made. Emotive or slanted language can be used in any kind of argument, but it is most common in evaluative arguments. 

False Analogy 

The false analogy supports a claim by comparing its subject to something not  essentially similar: “Offering courses in gay and lesbian theory is no more defensible than teaching pedophilia or necrophilia.” While both sides of the comparison refer to noncustomary sexual preference, there are more differences between gay theory and pedophilia than there are similarities, and comparing them attempts to prejudice the reader against gay and lesbian theory. As pointed out in Chapter 11, analogies can be useful in generating and illuminating arguments, but they can never prove a point. Just as legitimate comparison can be used to support any kind of argument, analogies can be misused in all of the four classes of argument. If you find that you have introduced an analogy to support rather than  explain or illuminate a claim, you have probably committed this  fallacy. 

Hasty Generalization 

Basically a misuse of the inductive method, hasty generalization consists of a general claim based on an insufficient sample: “Young professional people tend to be self-centered and materialistic. My friends Eric and Melanie certainly are.” This fallacy typically occurs in factual arguments and in the supposedly factual support for evaluative statements about entire groups of people: “Women are sentimental”; “Asian-American students are good in mathematics.” 

Non Sequitur 

A non sequitur claims a logical relationship between a conclusion and a premise where none exists: “Henry should make a good governor because he is tall and handsome.” Non sequitur in Latin means “it does not follow”; non sequitur reasoning is behind almost all fallacies. The term is really a generic one that has been specifically applied to cases where the relationship between a premise and a conclusion is seriously askew. The term is also used to cover some fallacies in causal analysis: “I performed poorly on that speech because I wore my green tie rather than my red one.” This is an example of our next fallacy—post hoc, ergo propter hoc. Non sequitur reasoning can occur in any category of argument. 

Post Hoc, Ergo Propter Hoc

Post hoc, ergo propter hoc is Latin, meaning “after this, therefore because of this.” It means claiming that because one event preceded another, it must have caused the subsequent event to occur: “I performed poorly on that speech because I wore my green tie rather than my red one.” This fallacy is at the root of much superstition, as in the case of a pitcher who carries a red handkerchief with him whenever he pitches because he had one with him the day of his no-hitter. It is a serious risk in any causal analysis, and a writer can guard against it by following the principles of causal reasoning presented in Chapter 8 (see book title below). 

Slippery Slope 

Designating a first and a last step in a causal chain, when the intervening steps have not occurred, constitutes the slippery slope fallacy: “I didn’t get the first job  I interviewed for, so I guess I’d better forget about a career as an engineer.” In this simple example, the speaker creates a worst-case scenario (forgetting about engineering) based on a series of events that has not yet occurred and will not necessarily occur, that is, repeated failure to be hired in engineering jobs. This fallacy appears most commonly in arguments of effect, usually when the writer wishes to prove that the consequences of a particular action are likely to be negative. 

Strawperson Argument 

A strawperson argument involves attacking a view similar to but not identical with that of an opponent: “How long will America tolerate softheaded opponents of gun control who want only criminals to have guns?” Advocates of gun control vary in their views, but they do not want only criminals to have guns. The adjective softheaded is an example of emotive language; in this sentence, it is designed to arouse a particular emotional response. Negative loaded terms are frequent in strawperson arguments. This fallacy is a common but misguided tactic of evaluative arguments. You can improve your ability to analyze your own and others’ arguments by familiarizing yourself with the kinds of fallacies previously defined, but you need to remember that what is considered “correct” thinking depends on your context. What may be incorrect in one context may be perfectly acceptable in another: ad hominem arguments are frowned on in academic writing (though they do occur), but they are perfectly acceptable in a court of law, where questioning and at least implicitly attacking witnesses’ backgrounds and motives are frequently practiced. In addition, some of these fallacies are only a slight step off the path of correct  reasoning. For example, there is nothing inherently fallacious about either-or reasoning, but this kind of reasoning goes wrong when either-or alternatives lead to excluding other, real possibilities.

Extracted from “Everyday Arguments ~ A Guide to Writing and Reading Effective Arguments" by Katherine J. Mayberry (2009)