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Informal Fallacies II

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Mark Thorsby

on 1 June 2011

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Transcript of Informal Fallacies II

Informal Fallacies 2
1. What is a Fallacy?
2. Yesterday We covered....
Fallacies of Relevance
Fallacies of Weak Induction
Fallacies of Presumption
Fallacies of Ambiguity
Fallacies of
Ordinary Language Fallacies
begging the question
(petitio principii)
Complex Question
False Dichotomy
suppressed evidence
In these fallacies, the premises either presume what they purport to show (as with the first two of these fallacies) or else presume distorted versions of the truth (as with the last two of these fallacies).
The fallacy of begging the question (petitio principii) occurs when the arguer uses some trick or device to hide the fact that a premise may not be true. When this fallacy is committed, the argument must be valid, one premise must be questionable, and some artifice must be employed to hide the questionable status of the premise in question.

One typical way of begging the question is simply to leave a crucial premise out of the argument altogether.

Another typical way of begging the question is to present a premise that more or less has the same meaning as the conclusion but is worded differently.

A third typical way of begging the question is to restate the conclusion as a premise in a long chain of inferences. Begging the question has also been called circular reasoning.
The fallacy of complex question occurs when an apparently single question is asked that really involves two or more questions, all of which are answered by any appropriate answer to the apparently single question. Such a question is the familiar "Have you stopped beating your wife?" which involves the two questions "Did you ever beat your wife?" and "If you did ever beat your wife, have you stopped?" The complex question, although not itself an argu ment, is such that the question, taken together with an answer to it, yields an argument that establishes the truth of some proposition presupposed in the question. Thus, the proposition presupposed in the question "have you stopped beating your wife?" is "You once did beat your wife," and whether the person answers "yes" or "no" to the question the truth of this proposi tion will be implied.
A dichotomy is a pair of alternatives (states, characteristics, or conditions) that are both mutually exclusive and jointly exhaustive. A pair X, Y is mutually exclusive if nothing can be both X and Y; it is jointly exhaustive if everything must be either X or Y. A false dichotomy is a pair of alternatives, presented as if it were a dichotomy when it is not in fact a dichotomy. The fallacy of false dichotomy is committed when an argument rests for its goodness on presenting some pair of conditions as if it were a dichotomy when it is not. The usual method is to present a false dichotomy in a premise with the either ... or form, known as a disjunctive premise. The argument then proceeds fallaciously in one of two ways. First, one of the alternatives is denied and the other is concluded to. When the alternatives are not jointly exhaustive (or in other words, when the disjunctive premise is simply not true), this procedure is fallacious, though the argument looks like the valid argument form known as disjunctive syllogism. Second, one of the alternatives is affirmed and the denial of the other is concluded to. When the alternatives are not mutually exclusive, this procedure is fallacious, though the argument looks like a valid argument form using the so-called "exclusive or."
The fallacy of suppressed evidence is a fallacy of presumption that is closely related to begging the question. It consists in passing off what are at best half-truths as if they were the whole truth and using them as premises in an argument. This fallacy is also committed if an arguer presents the premises in such a way as to imply that they are the only facts relevant to the conclusion when in fact there are other relevant facts that point in the opposite direction. One example of such a fallacy is, "You ought to become a Hollywood starlet; starlets are so glamorous, they make money easily, and they quickly rise to full-fledged stardom."
The fallacies of ambiguity include equivocation and amphiboly. In both cases the faultiness of the argument arises because of some ambiguity in either the premises or conclu sion or both.
The fallacy of equivocation occurs when the inference in an argument depends on the fact that a word or phrase is used in two or more different senses. For example, "Banks have lots of money in them; the sides of rivers are banks; therefore, the sides of rivers have lots of money in them," is an argument in which the inference depends on the word "banks," which is equivocated upon (used with different senses) in the argument.
The fallacy of amphibolyoccurs when an arguer, beginning with some statement that is ambiguous owing to its syntactical structure, proceeds to interpret it in a way in which it was not intended and to draw a conclusion based on this faulty interpretation. The original statement is usually made by someone other than the arguer. The syntactical ambiguity is often due to mistakes in grammar or punctuation, such as dangling modifiers, confusion of restrictive and nonrestrictive clauses and phrases, and ambiguous reference of pronoun to antecedent. A well known example of amphiboly is Groucho Marx's classic "One morning I shot an elephant in my pajamas. How he got into my pajamas I'll never know."
The main difference between amphiboly and equivocation is that in amphiboly the ambiguity is traceable to syntactical structure in a statement, whereas in equivocation the ambiguity is traceable to a word or phrase that has two or more distinct senses. If the ambiguity in an argument can be removed by a syntactical or grammatical alteration, such as a change in punctuation or a rearrangement of words, it is an amphiboly. If the ambiguity is removable only by a substitution of different terms, it is probably an equivocation.
In these fallacies arguments are employed that, though faulty, are grammatically analogous to other arguments that are unimpeachable. The similarity in linguistic structure makes the fallacious, argument appear good. In composition and division the faultiness in the argument arises because an attribute or characteristic is improperly transferred from parts of a whole to the whole or from the whole itself to its parts.
The fallacy of composition occurs when the inference in an argument depends on the erroneous transference of a characteristic from the parts of something to the whole. For instance, going from a distributive predication to the corresponding collective predication is one sort of fallacy of composition. Another would be going from the characteristics of the elements of a chemical compound to the characteristics of the compound ("Hydrogen and oxygen are gases; therefore, H z0 is a gas").
The fallacy of division occurs when the inference in an argument depends on the erroneous transference of a characteristic from a whole to some one or more of its parts. Division is the exact reverse of composition.
Composition and division are sometimes confused with hasty generalization and accident, respectively. Composition can be distinguished from hasty generalization as follows: in hasty generalization, the conclusion is not an assertion about a group taken as a whole (a collective predication); rather, it is an assertion about all (each and every one of) the members of a group (a distributive predication). But in composition the assertion in the conclusion is a collective predication. Similarly, division can be distinguished from accident as follows: in accident the inference is from a general assertion (a distributive predication) to a specific assertion, but in division the inference is from an assertion about a group taken as a whole (a collective predication) to an assertion about the members of the group.
Detecting Fallacies
Avoiding Fallacies
Fallacies in Ordinary language are difficult to detect:

1) There are many ways of making mistakes in argumentation
2) Many variations of fallacious thinking exist
3) Many fallacies can be mixed together in ordinary language
4) Many arguments have unexpressed conclusions & premises
The Newspaper Example - page 172
What Fallacies do you detect?
- ad hominem
- straw man
- question begging
How to Detect Fallacies?
1. Alertness
2. What is the conclusion of the argument?
3. What are the reason given?
4. Are the reasons relevant, supportive, accurate
5. What assumptions are being made?
6. Which premises are irrelevant?
Why do people commit fallacies?
1. Intent
Reason for Fallacy
How to Avoid
Moral Education
2. Careless Mental Posture
Acute Mental Discipline
3. Emotional Disposition
Stoic Attitude
4. One's Paradigm - Worldview
Acknowledge & Question
See Some Examples - page 176
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