(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)