The Logic of Inquiry: Rhetorical Devices ___________________
Both inductive and deductive arguments, even when properly formed, may result in invalid conclusions if the terms of the argument are not properly formed. The study of these sorts of errors (called “fallacies”) is called “rhetoric.” There are seven main fallacies: Fallacy of Relevance: The argument does not relate to the issue it is supposed to be addressing.
- Ad hominem (“personal attack”)—“If you can’t argue the case, argue against the person making the case”
- Ad bellum (“appeal to force”)—“Might makes right.”
- Ad ignorantium (“appeal to ignorance”)—“You can’t prove it’s not true, so I’m right,” or, as Bart Simpson puts it, “I didn’t do it. Nobody saw me. You can’t prove it.”
- Ad misericordium (“appeal to pity”)—“If you don’t fund this project, hundreds of people will be thrown out of work.”
- Ad populum (“appeal to the gallery”)—“All the polls support this position.”
- Ad vericundium (“appeal to authority”)—“Smith & Jones (1997) say this is the way to go.”
- Post hoc, ergo propter hoc (“false cause”)—The Latin words mean “It came after this, so it must be because of this.” For example, “Students moved in, and there went the neighborhood.”
Accident & Hasty Generalization: This fallacy occurs by moving from the group to the individual (when the group characteristic is not universal), and from the particular to the universal. For example, “People in this neighborhood have incomes above $100,000; you live in this neighborhood, so your income must be above $100,000” may or may not be true—it depends on whether the group characteristic (“income above $100,000”) is a universal (“in order to live in this neighborhood, you must have an income above $100,000) or a generalization (“the average income in this neighborhood is above $100,000”). Similarly, “This crow is black, so all crows are black” may or may not be true—if all birds in the family “crow” must have black feathers, then it is true; but if the color of the feathers is accidental (e.g., can there be albino crows?), then it is not. Complex Question: This fallacy occurs when two (or more) questions are combined into one, such as “Have you stopped beating your children yet?” This assumes two questions—“Have you ever beaten your children?” and “If so, have you stopped beating your children?” Begging the Question: This fallacy occurs when the answer to a question assumes what the question was asking in the first place, rather than providing proof (circular reasoning). For example, “Your work does not meet performance standareds because it is unsatisfactory.” (And why is it unsatisfactory? Because it fails to meet performance standards!). Irrelevant Conclusion: This is similar to begging the question, except that a conclusion is offered which appears to answer the question, but it does not necessarily come from the data which were offered in evidence. For example, “Look at all the effort I am putting forth; of course I’m an effective manager!” (as if effort and effectiveness were the same thing). Fallacy of Ambiguity: A shift in the meaning of the middle term creates the appearance of a valid argument:
- Equivocation: The same term is used, but with different meanings (“All men are mortal. Jane is not a man. Therefore Jane is not a mortal.”)
- Amphiboly: The grammatical structure itself permits different meanings (“Time flies like an arrow; fruit flies like an apple”)
- Accent: Emphasis changes the meaning (“You did something right!” –implying that you usually don’t).
Excerpted from URSI 609--Applied Quantitative Analysis by Tony Filipovitch
(The claim that there are seven main types of fallacies, followed by a listing of only six is how it appears in the original. I'm not sure if this is a gaffe, a clever joke, or an example of one of the types of fallacies (Perhaps a fallacy of ommission.) |
