Illicit Major

Alias: Illicit Process of the Major Term

Type: Illicit Process


Any form of categorical syllogism in which the major term is distributed in the conclusion, but not in the major premiss.

Example Counter-Example
All communists are leftists.
No conservatives are communists.
Therefore, no conservatives are leftists.
All dogs are animals.
No cats are dogs.
Therefore, no cats are animals.
Venn diagram

Venn Diagram:

This diagram represents both the Example and Counter-Example. It does not show the conclusion, "No S is P", to be true, because the area with the question mark is not shown to be empty.


An "illicit process of the major" is not an illegal trial of a military officer, rather it is a syllogistic fallacy in which the major term is undistributed in the major premiss, but distributed in the conclusion, which is the "illicit process"—that is, "illicit" distribution, in the sense of breaking the rules of the categorical syllogism.

Sibling Fallacy: Illicit Minor


Irving Copi & Carl Cohen, Introduction to Logic (Tenth Edition) (Prentice Hall, 1998), pp. 276-7.