Logical Fallacy

Etymology:

The English word "fallacy" comes from the Latin noun "fallacia", meaning "trick" or "fraud". "Fallacia" is related to the Latin verb "fallere", meaning "deceive", so that a "fallacia" is a deception. The English words "false", "fail", "fallible", and "fault" are all derived from these same Latin words.

Source: John Ayto, Dictionary of Word Origins (1991)

Exposition:

The English word "fallacy" is both vague and ambiguous. Its general meaning is "mistake" or "error", especially a common one. For instance, "fallacy" is frequently used to mean a common factual error, and a number of books that use it in the title—such as Tad Tuleja's Fabulous Fallacies and the Reader's Digest book Facts & Fallacies—are collections of common factual mistakes with corrections. This is not the type of fallacy catalogued in The Fallacy Files; rather, it is a collection of logical fallacies.

"Logical fallacy" shares with "factual fallacy" the genus "common error", that is, both are types of error commonly committed by people. Factual fallacies, of course, are mistakes about factual matters, whereas logical fallacies are not errors of fact, but errors of reasoning. Thus, a logical fallacy is a common error in reasoning.

Exposure:

Subfallacies: