Does anyone have a simple, easily understood definition of "logical fallacy" that can be used to explain the concept to people who have never heard of it before?

I was trying to explain the idea to a friend a few days ago but since I didn't have a definition I had to show her She understood the concept quickly, but it would be much more reliable and eloquent to actually define it.

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I don't think this is so simple to explain, because to really understand logical fallacies you need to understand what a proof is. Not a lot of people understand what a proof is.

7Qiaochu_Yuan6yYou think she would've understood the concept even more quickly if you had a definition? I think people underestimate the value of showing people examples as a way of communicating a concept (and overestimate the value of definitions).
0pragmatist6yIt's a bad concept, at least the way it's traditionally used in introductory philosophy classes. It encourages people to believe that certain patterns of argument are always wrong, even though there are many cases in which those patterns do constitute good (non-deductive) arguments. Instructors will often try to account for these cases by carving out exceptions ("argument from authority is OK if the authority is actually a recognized expert on the topic at hand"), but if you have to carve out loads of exceptions in order to get a concept to make sense, chances are you're using a crappy concept. Ultimately, I can't find any unifying thread to "logical fallacy" other than "commonly seen bad argument", but even that isn't a very good definition because there are many commonly seen bad arguments that aren't usually considered logical fallacies (the base rate fallacy, for instance). Also, by coming up with cute names to label entire patterns of argument, and by failing to carve out enough exceptions, most expositions of "logical fallacy" end up labeling many good arguments as fallacious. So I guess my advice would be to stop using the concept altogether, rather than trying to explicate it. If you encounter a particular instance of a "logical fallacy" that you think is a bad argument, explain why that particular argument doesn't work, rather than just saying "that's an argumentum ad populum" or something like that.

Open thread, January 25- February 1

by NancyLebovitz 1 min read25th Jan 2014318 comments


If it's worth saying, but not worth its own post (even in Discussion), then it goes here.