non distributio medii en · NOUN
Etymology
From Latin, literally "undistributed middle".
Meanings
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(uncountable) A logical fallacy that is committed when the middle term in a categorical syllogism isn't distributed.
An educated man must be in some sort instructed; but it is a mere non distributio medii to say that an instructed person must be an educated person.
1932, Albert Jay Nock, The Theory of Education in the United States: