It may be said that disjunctive arguments depend on _two_ rules. This is the first: _The major premise must assert a logical disjunction._ A logical disjunction involves two requisites; first, the alternatives must be _mutually exclusive_; second, the _enumeration_ must be _complete_. _Illustrations of illogical major premise._ _Terms not mutually exclusive_: This boy is either inattentive or indolent, He is not inattentive, ∴ He is indolent. It is obvious that the boy might be _both_ inattentive and indolent. Experience teaches that the qualities are usually concurrent, and to assume that the boy must be either one or the other is a clear case of “begging the question.” Some logicians maintain that “_either――or_” signify that both alternatives _cannot be false_, but that both _may be true_. If this viewpoint were adopted, the major premise of the illustration would _not_ be a case of begging the question. It is unnecessary to argue the point, if it is made perfectly clear which view is to obtain in this discussion. Briefly stated the two points are these. First opinion: “_Either――or_” when used logically, mean that if the first alternative is false the second must be true, or if the first alternative is true the second must be false. Second opinion: “_Either――or_” when used logically mean that if the first alternative is false, the second must be true; but if the first alternative is true, the other may or may not be true. _This treatise adopts the first opinion._ With us all alternative arguments to be logical must be mutually contradictory; i. e., _when one is false, the other must be true and when one is true the other must be false; both_ cannot be false, neither can _both_ be true. When it is intended that this implication should not obtain, then the expressed alternative will take this form, “The boy is either inattentive or indolent or _both_.” Other examples where the terms of the disjunctive may not be mutually exclusive: (1) “Lord Bacon was either exceedingly studious or phenomenally bright.” (Undoubtedly he was both.) (2) “This teacher is a graduate either of Harvard or of Yale.” (Perhaps both.) (3) “The defendant is either a liar or a thief.” (The one often leads to the other.) (4) “To succeed one must either seize the opportunity as it passes or make his own.” (The best success results from doing both.) _Incomplete enumeration_: The cause of the disease was either the water or the milk, It was not the milk, ∴ It was the water.