Informal Fallacies

Fallacy Classified | Informal Fallacy | Fallacy of Relevance | Demo | Fallacy of Ambiguity | Avoid Fallacies

What is a fallacy?

A fallacy is a blunder in reasoning. It is "false" reasoning, that is to say, reasoning with illogical argument or misleading argument. Reasoning means drawing inferences or conclusions from known or assumed facts or premises. The premises and conclusions of arguments should qualify as propositions, i.e., the meanings of declarative sentences which possess the essential characteristic of being either true or false. Recall that an argument is defined as a series of connected declarative sentences (premises) in support of another statement (conclusion) or a position. A fallacy consists of invalid or unwarranted inference of a conclusion from premises some of which may not qualify as propositions. Commands, exhortations, or exclamations do not possess the quality of truth or falsity and must be reworded into propositions if they are to serve as either premises or conclusions.

How are fallacies classified?

Fallacies may be broadly classified as either formal or nonformal fallacies. Formal fallacies are invalid inferences of conclusions from premises, the invalidity being due to the form of the argument. Nonformal, known more as informal fallacy, as a category includes a multiplicity of mistakes in reasoning, some of which involve careless use of language. Informal fallacy can be thought of as counterfeit argument, i.e., a type of argument that may seem to be correct but which proves on examination not to be correct. Informal fallacies, unlike formal fallacies, are not fallacies of form. Extralogical or emotional appeals usually constitute one of the sources of persuasion. In other cases, informal fallacies are deceptive pieces of "bad" English or mistakes due to ambiguity or vagueness of a term or phrase, or an entire sentence. In any case, the pretense of logical relevance, we could say, is the source of fallacy.

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Fallacies of Form

Fallacies of form render arguments invalid irrespective of the content of the argument or the truth or falsity of its propositions. If the form of an argument allows an inference of a false conclusion from all true premises, then we know the argument to be invalid, for a valid argument will never result in the deduction of false conclusion from true premises. Indeed, if it so happens that the conclusion of a particular argument is known to be false, and the argument is valid, then we know that one or more of the premises is false as well. (See Study 4 for fallacies of form and some of the variations.)

Informal Fallacies

In reasoning that "If X looks like a Z, walks like a Z, talks like a Z, and even reasons like a Z, well then, X must be a Z," one runs the risk of accepting a counterfeit for the real thing. Informal fallacies are counterfeit arguments in that they consist of premises and conclusions which are related, it is claimed, as conclusions drawn logically from true premises. But herein lies the error. While there is a connection between premises and conclusion in such arguments, the connection is a psychological one masquerading as a logical relation between premises and conclusion in a particular argument. The mistake is one of confusing an emotional appeal for a logical one. An emotional appeal seeks to persuade you to accept a conclusion solely on its appeal to feelings of attraction or aversion to a particular object or set of objects or events. Many commercials make use of attraction and/or aversion for things or circumstances to persuade one to avoid something by buying a product, or to attain an attractive status by using a product. When their effect is to cause you to confuse an emotional appeal for a logical one, we can say that they make use of counterfeit argument to achieve acceptance of a conclusion. One should not ignore the context in determining whether a piece of language is functioning as counterfeit argument.

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Informal fallacy classifications abound. Perhaps the simplest consists of two categories of the most common types: (1) fallacies of ambiguity and vagueness; and (2) fallacies of irrelevant conclusion.

Fallacies of Relevance

Fallacies of irrelevant conclusion are those for which the premises are not relevant to the truth of the conclusion. With such, the label non sequitur, meaning literally that the conclusion does not follow from the premises is often used. With these fallacies the premises are incapable of establishing the conclusion because they are logically irrelevant to the conclusion. Some of the more common informal fallacies have been given Latin names which have become part of the English language.

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Argumentum ad hominem abusive (AH) when irrelevancies of character, circumstances, the beliefs or prejudices of the person are used for rejection a position.
Argumentum ad baculum (AB) when one appeals to force or the threat of force instead of reasons to cause acceptance of a conclusion.
Argumentum ad misericordiam (AM) when one appeals to pity instead of sound reasoning to gain acceptance of a conclusion.
Argumentum ad populum (AP) when one attempts to gain popular assent to a conclusion by arousing the feelings and enthusiasms of the multitude.
Argumentum ad verecundiam (AV) when instead of sound argument one appeals to the feeling of respect people may have for the famous to win assent to a conclusion.
Argumentum ad ignorantiam (AI) whenever it is argued that a proposition is true solely on the basis that it has not been proved false, or that it is false because it has not been proved true.
False Cause (FC) when one infers that because one event follows another, the first event caused the second.
False Dilemma (FD) when one calls for a conclusion based on the assumption that two and only two mutually exclusive alternatives are possible when in fact more than two are possible or the two are not mutually exclusive.
Accident (A) when it is argued that what is true in general is true universally and without qualification.
Hasty  Generalization (HG) when in argument one considers only exceptional or too few cases and generalizes to a rule that fits them alone.
Circular Reasoning (CR) when one assumes as a premise for an argument the very conclusion that is intended to be proved.
Complex Question (CQ) when in argument one treats a plurality of questions as if it were a simple one demanding a single answer.
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The following example has limited value. The intent is to describe communication with potential for counterfeit argument. While these statements are not explicit formulations of premises or conclusions, they are intended to illustrate possible instances of informal fallacies. Readers should use their imaginations to round out a context with the appropriate elements of oral expression. Imagine this setting: a young couple is discussing an accumulation of incidents that perhaps signals the end of their honeymoon.

She "You're just like your father--lazy and sloppy!" (AH)
He "You wouldn't talk that way in front of my dad!" (AB)
She "Maybe not, but I get no help from you; after 40 hours of hard work, I do all, I mean all the house cleaning and cooking while you watch TV?" (AM)
He "All women who want both career and marriage seem to feel very happy about doing both! That's what all successful women say." (AP)
She "Would Mr. Rogers, your hero, hold the opinions you have about marriages and careers?" (AV)
He "Mr. Rogers has never argued that career and marriage are incompatible for women. Therefore, he must believe that they are compatible." (AI)
She "Don't talk to me about Mr. Rogers. The last time you brought him into our discussion, we had a terrible fight!" (FC)
He "I didn't bring Rogers into our discussion, you did! You either like him or you don't; I see you don't!" (FD)
She "It's not a question of liking Rogers or not. It's the way you use what he says. One should never take what other people say out of context, as you do with Mr. Rogers." (A)
He "This is the third time you have accused me of using what Mr. Rogers' says. When you run out of good arguments, you always say this about me." (HG)
She "This is just like you! You conclude that you are innocent of any wrong-doing because you are innocent of any wrong-doing!" (CR)
He "When will you stop hassling me?" (CQ)

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Now, that a counterfeit argument may fit into more than one category is not disputed. In such cases, perhaps more information about the context is required. However, even with exhaustive information about the context, one may find it difficult, if not impossible, to classify a particular counterfeit argument into one and only one category. Language serves multiple purposes. Reasoners sometimes operate with hidden agendas or motives. In cases where there exists the possibility of classifying a counterfeit argument into more than one known category, we can agree that it is one or the other, and possibly both. This should not preclude effort to classify counterfeit arguments based on the defining characteristics of known categories.

Fallacies of Ambiguity

Fallacies of ambiguity occur in formulations of argument that use ambiguous words or phrases. This is a smaller class of fallacies that include the fallacies of equivocation, amphiboly, composition, and division. Definitions follow.

equivocation (EN) when one confuses in argument the different meanings a single word or phrase may have.
amphibology (AY) when in argument a statement's meaning is unclear because of the loose or awkward way in which the words are combined.
accent (AT)     when in argument words or phrases of a statement are emphasized or stressed producing quite different meanings from the original.
composition (CN)            when in argument one reasons fallaciously from the properties of the part or parts to the properties of the whole itself.
division (DN) when in argument one reasons fallaciously that what is true of a whole must also be true of each of the whole's parts.

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It is not difficult to come up with examples of each of the above.  Some uses are mere play on words as in "Good steaks are rare these days, so don't order yours well-done" where the equivocation turns on the meanings of "rare." More serious perhaps, is this one:"The end of a thing is its perfection; death is the end of life, Therefore, death is the perfection of life." (EN) (Examine the meanings of "end." )With this next example, the ambiguity lies in the structure or syntax of the sentence: "Leaking badly manned by a starved and thirsty crew one infirmity after another overtakes the little ship." (AY) Obviously, the phrase "manned . . . crew" needs to be relocated, perhaps at the end of the sentence to achieve clarity of meaning. The statement, "We should not speak ill of our friends," when quoted as: "We should not speak ill of OUR FRIENDS" (AT) stresses words not emphasized in the original conveying different meaning(s) from the original.Top of Page Composition and division are closely related. For example, if one argues that based on the properties of the elements of NaCl, the compound must be highly toxic (CN), one might suspect that the person knows little or nothing about chemistry or does not know that the compound is table salt, perhaps both. On the other hand, if someone argued that since salt possesses a class of salutary properties; therefore, the salt's elements (sodium and chloride) must be salutary, instruction in chemistry and perhaps more would seem to be necessary.  

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How can one avoid informal fallacies?

It was suggested above that one should not ignore the context in determining when to label something as informal fallacy. For example, when there is no attempt to disguise an emotional appeal as a logical appeal, there may be no point in accusing someone of using informal fallacy. Or, when all logical appeals have failed to convince a perverse arguer who knowingly and willfully disregards truth for error, what else remains but ad hominem (not the abusive variety) or even some ad baculum language? Silence? No doubt there are occasions where the use of threatening language may be the only alternative; for example, a police officer confronted by an armed felon. Ad hominem must not be confused with the abusive kind. Ad hominem is a form of argument that assumes the propositions of another for the sake of deducing contradictions or conclusions unacceptable to the person holding the position. There are special circumstances where it is quite appropriate to direct a complex question to another; for example. "Where did you hide the body?" or "Do you know the penalty for perjury?" are questions that are not conceived as instances of informal fallacy, once the groundwork has been set down for their use. The context is important.What can one do to avoid informal fallacy as counterfeit argument? It should be evident that telling someone that he or she is engaging in ad hominem abusive reasoning may not have the desired effect of causing the person to pause and reflect on his or her thinking. The person may not know what you mean by ad hominem, or informal fallacy. What then? Nevertheless, identification of the counterfeit argument by correct label is an important first step. A second step requires clear definitions of ambiguous or vague terms. A third step constructs a counterexample, analogous in every respect with the informal fallacy in which the premises are obviously true and the conclusion obviously false.

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For example, suppose someone argues: "If President Kennedy was assassinated, then he is dead. Now, all acknowledge that he is indeed dead. Therefore, President Kennedy was assassinated."This argument is fallacious, guilty of the fallacy of affirming the consequent. Constructing a counterargument to make explicit the fallacious reasoning requires that (1) the propositions be of the same form as the original, (2) the format be identical to the original, and (3) the premises be true and conclusion be false. An appropriate response could be worded in this way:"You may just as well argue that if President Johnson was assassinated, then he is dead. President Johnson is dead. Therefore, President Johnson was assassinated."Obviously, the conclusion of the counterargument does not follow from the true premises. Similarly, the conclusion of the previous argument is not necessitated by its premises.

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