Either a sinner must repent or he will be damned. .'. Either a sinner must repent or he will not be saved. § 721. _Conversion by Negation of Complex Propositions._ (A) If A is B, C is always D. .'. If C is not-D, A is never B. (E) (E) If A is B, C is never D. .'. If C is D, A is always not-B. (A) (I) If A is B, C is sometimes D. .'. If C is D, A is sometimes not not-B. (O) (O) If A is B, C is sometimes not D. .'. If C is not-D, A is sometimes B. (I) (E per acc.) If A is B, C is never D. .'. If C is not-D, A is sometimes B. (I) (A per ace.) If A is B, C is always D. .'. If C is D, A is sometimes not not-D. (O) § 722. (A) If a man is a smoker, he always drinks. .'. If a man is a total abstainer, he never smokes. (E) (E) If a man merely does his duty, no one ever thanks him. .'. If people thank a man, he has always done more than his duty. (A) (I) If a statesman is patriotic, he sometimes adheres to a party. .'. If a statesman adheres to a party, he is sometimes not unpatriotic. (O) (O) If a book has merit, it sometimes does not sell. .'. If a book fails to sell, it sometimes has merit. (I) (E per acc.) If the wind is high, rain never falls. .'. If rain falls, the wind is sometimes high. (I) (A per acc.) If a thing is common, it is always cheap. .'. If a thing is cheap, it is sometimes not uncommon. (O) § 723. When applied to disjunctive propositions, the distinctive features of conversion by negation are still discernible. In each of the following forms of inference the converse differs in quality from the convertend and has the contradictory of one of the original terms (§ 515). § 724. (A) Either A is B or C is always D. .'. Either C is D or A is never not-B. (E) (E) Either A is B or C is never D. .'. Either C is not-D or A is always B. (A) (I) Either A is B or C is sometimes D. .'. Either C is not-D or A is sometimes not B. (O) (O) Either A is B or C is sometimes not D. .'. Either C is D or A is sometimes not-B. (I) § 725. (A) Either miracles are possible or every ancient historian is untrustworthy. .'. Either ancient historians are untrustworthy or miracles are not impossible. (E) (E) Either the tide must turn or the vessel can not make the port. .'. Either the vessel cannot make the port or the tide must turn. (A) (1) Either he aims too high or the cartridges are sometimes bad. .'. Either the cartridges are not bad or he sometimes does not aim too high. (0) (O) Either care must be taken or telegrams will sometimes not be correct. .'. Either telegrams are correct or carelessness is sometimes shown. (1)