Moving the Goalposts

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Sometimes thought of as the opposite of a Texas Sharpshooter, “moving the goalposts” is a way of changing the criteria for proving the validity of an argument, often after they have already been met. As Rationalwiki points out that certain movements seem prone to doing it more than others, but I’ve seen this fallacy used by a lot of people. Listserve debates are a common place for this as a rhetorical tactic, although listserve debates are generally a great source of examples of every form of logical fallacy.

Texas Sharpshooters

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A “texas sharpshooter” is someone who fires at the side of a barn and then draws bull’s eyes around the bullet holes. It’s a common logical fallacy used to show false causation. Watch out for claims based on isolated bits of data, especially if there is no broader context.

More here and here.