(A) If a mother loves her children, she is always kind to them.
.'. If a mother loves her children, she is never unkind to
them. (E)
(E) If a man tells lies, his friends never trust him.
.'. If a man tells lies, his friends always distrust him. (A)
(I) If strangers are confident, savage dogs are sometimes friendly.
.'. If strangers are confident, savage dogs are sometimes not
unfriendly. (O)
(O) If a measure is good, its author is sometimes not popular.
.'. If a measure is good, its author is sometimes
unpopular. (I)
§ 720. The disjunctive proposition may be permuted as it stands without being reduced to the conjunctive form.
Either A is B or C is D.
.'. Either A is B or C is not not-D.
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)