undistributed middle

American  

noun

1. Logic. a middle term of a syllogism that does not refer to its entire class in the major premise or minor premise, with the result that the syllogism is not valid.

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Etymology

Origin of undistributed middle

First recorded in 1820–30

Example Sentences

See Examples For:

undistributed middle

Affirmation of the consequent of a disjunctive is equivalent to the same fallacy in the semi-conjunctive form, and therefore involves the ordinary syllogistic fallacy of undistributed middle.

From Deductive Logic by St. George William Joseph Stock

"It will make me simply ill—I could never describe to you," said Miriam, with her face aglow, "what it is to me to hear some silly man drone away with an undistributed middle term."

From Pointed Roofs Pilgrimage, Volume 1 by Dorothy Miller Richardson

This fallacy, which is not uncommon in practice where the terms are complicated, is known as the fallacy of the undistributed middle.

From The Making of Arguments by J. H. Gardiner

The solution to the paradox lies in discovering that the term "population" is used in two different senses, thus exposing the logical fallacy of the undistributed middle.

From Anything You Can Do ... by Randall Garrett

If any proposition, therefore, but the first were particular, there would be a particular major, which involves undistributed middle, if the minor be affirmative, as it must be in the first figure.

From Deductive Logic by St. George William Joseph Stock