Logical Fallacies逻辑谬论.ppt

Logical Fallacies Continuing our foray into the world of Argument Courtesy of: /depts/wcweb/handouts/fallacies.html What is Fallacy? Fallacies are defects that weaken arguments. First, fallacious arguments are very, very common and can be quite persuasive, at least to the causal reader or listener. You can find dozens of examples of fallacious reasoning in newspapers, advertisements, and other sources. Second, it is sometimes hard to evaluate whether an argument is fallacious. An argument might be very weak, somewhat weak, somewhat strong, or very strong. An argument that has several stages or parts might have some strong sections and some weak ones. Hasty Generalization Definition: Making assumptions about a whole group or range of cases based on a sample that is inadequate (usually because it is atypical or just too small). Stereotypes about people (frat boys are drunkards, grad students are nerdy, etc.) are a common example of the principle underlying hasty generalization. Example: My roommate said her philosophy class was hard, and the one Im in is hard, too. All philosophy classes must be hard! Two peoples experiences are, in this case, not enough on which to base a conclusion. Missing the Point Definition: The premises of an argument do support a particular conclusion--but not the conclusion that the arguer actually draws. Example: The seriousness of a punishment should match the seriousness of the crime. Right now, the punishment for drunk driving may simply be a fine. But drunk driving is a very serious crime that can kill innocent people. So the death penalty should be the punishment for drunk driving. The argument actually supports several conclusions-- The punishment for drunk driving should be very serious, in particular--but it doesnt support the claim that the death penalty, specifically, is warranted. Post hoc (false cause) This fallacy gets its name from the Latin phrase post hoc, ergo propter hoc, which translates as after this, there