The distribution rule is a logic rule used to test validity. There are three rules for testing validity:

1. The number of negative premises must equal the number of negative conclusions.
2. The middle term must be distributed once.
3. Any terms distributed in the conclusion must be distributed in a premise.

A term within a proposition is said to be distributed when a claim is made concerning every member of the class denoted by the term.

A statements are distributed in subject term, E statements are distributed in both subject and predict term, I statements are not distributed both, O statements are distributed predict term,