Fallacy of Undistributed Middle

Fallacy

By Middle Term of Valid Categorical Syllogism is Distributed at least Once, the middle term of a valid categorical syllogism is distributed in at least one of the premises.

To express a syllogism where this rule is violated is to commit the fallacy of the undistributed middle.

Sources

• 1965: E.J. Lemmon: Beginning Logic ... (previous) ... (next): $\S 4.4$: The Syllogism: Exercises: $\text{A}$: Rules of Quantity: $2$: Footnote