(A) If a man is honest, he is always truthful.
.'. If a man is untruthful, he is always dishonest.
(O) If a man is hasty, he is sometimes not malevolent.
.'. If a man is benevolent, he is sometimes not unhasty.
§ 729. As applied to disjunctive propositions conversion by contraposition consists simply in transposing the two alternatives.
(A) Either A is B or C is D.
.'. Either C is D or A is B.
For, when reduced to the conjunctive shape, the reasoning would run thus—
If A is not B, C is D.
.'. If C is not D, A is B.
which is the same in form as
All not-A is B.
.'. All not-B is A.
Similarly in the case of the O proposition
(O) Either A is B or C is sometimes not D.
.'. Either C is D or A is sometimes not B.