Rule 3: The conclusion cannot contain any term that is not “distributed” in at least one premise (either the major premise or the minor premise).
As we have just seen from Rule 2, supra, a term is “distributed” when it refers to every member in its entire class. To be logically valid an argument cannot contain a distributed conclusion (e.g., one that pertains to “all,” or to “every” member of the affected class) that is derived from a non-distributed major or minor premise (e.g., one that refers to “some,” “many” or LESS THAN ALL members of the class). The reverse of this rule is also true.
An example of this Rule is illustrated by the following syllogism:
(1)   Law students who lack good reasoning skills (major term) should study logic.

(2)   Many law students (minor term) lack good reasoning skills.

(3)   Therefore, ALL law students should study logic.

  vstudent studying at desk

Statement 1, supra, (referring to “law students who lack good reasoning skills”) is NOT a universal (i.e., “distributed”) statement, since (as this statement at least implies) there may be some law students who do have good reasoning skills. Likewise, Statement 2, supra, (referring to “many law students”) is obviously not a universal statement. Thus, the conclusion is invalid because it is not distributed in either the major or the minor premises, yet it is distributed in the conclusion (that pertains to ALL law students).