Distribution rule

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,