The Ignoratio elenchi reference article from the English Wikipedia on 24-Jul-2004
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Ignoratio elenchi

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Ignoratio elenchi (also known as irrelevant conclusion) is the logical fallacy of presenting an argument that may in itself be valid, but which proves or supports a different proposition than the one it is purporting to prove or support. "Ignoratio elenchi" can be roughly translated by ignoring the issue; "elenchi" is from the Greek ελεγχος, meaning an argument of disproof or refutation.

Examples:

Aristotle believed that an ignoratio elenchi is a mistake made by a questioner while attempting to refute a respondent's argument. He called it an ignorance of what makes for a refutation.

External link

Stephen's Guide: Irrelevant Conclusion