Anecdotal Evidence


The argument draws a conclusion from cases specifically chosen to support the conclusion.



The fallacy is sometimes called "cherry picking." This fallacy can seem similar to Hasty Generalization. The difference is this: in the fallacy of Hasty Generalization we genuinely consider the case or cases first, and then draw a conclusion from them (albeit hastily); in the fallacy of Anecdotal Evidence we know in advance what conclusion we are trying to support, and then select those cases (and only those cases) that support it, often ignoring or overlooking cases that would undermine our conclusion. Hasty Generalization is a fallacy because it is sloppy; Anecdotal Evidence is a fallacy because it is disingenuous.



"Criminals hardly ever get the punishment they deserve. Consider the Nigerian gang rape case. A bunch of boys gang raped a girl nearly to death--she is still in a wheelchair--but they were just sentenced to mowing the lawn of the police station, and then they were let go."


"Abortion is morally wrong. In one case a woman had an abortion merely so her pregnancy would not interfere with a trip to Europe that she and her husband were planning."



There is, of course, nothing wrong with presenting representative cases to illustrate an Inductive conclusion properly drawn from a fair and representative sample. The representative case serves to put a human face on what would otherwise be just a mass of cold statistics. However, it is the Inductive argument as a whole (i.e. all those cold statistics) that justifies the conclusion. The anecdote merely illustrates and humanizes the properly drawn conclusion.

The fallacy of Anecdotal Evidence mimics this legitimate use of illustrative story-telling. It presents us with a case that puts a human face upon a conclusion. The fallacy of Anecdotal Evidence errs, however, in using the single case in place of the properly conducted study. The fallacy implies that the anecdote is illustrating a properly drawn conclusion, when in fact no such properly conducted study exists, or, if it does, the story offered does not genuinely represent the study's actual results.


Source: In Novum Organum, 1620, Francis Bacon describes the tendency to pick out evidence that supports ones own preconceptions. The term "anecdotal evidence" is in common usage, and I doubt that an original source for the term can be identified.


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