E.O., these plainly stand to one another in a Square of Opposition, just as Categoricals do.
Thus A.and E.( _If A is B, C is D_, and _If A is B, C is not D_) are contraries, but not contradictories; since both may be false (_C_ may sometimes be _D_, and sometimes not), though they cannot both be true.
And if they are both false, their subalternates are both true, being respectively the contradictories of the universals of opposite quality, namely, I.of E., and O.of A.But in the case of Disjunctives, we cannot set out a satisfactory Square of Opposition; because, as we saw (chap.v.Sec.

4), the forms required for E.and O.are not true Disjunctives, but Exponibles.
The Obverse, Converse, and Contrapositive, of Hypotheticals (admitting the distinction of quality) may be exhibited thus: DATUM.

OBVERSE.
A._If A is B, C is D_ _If A is B, C is not d_ I.Sometimes _when A is B, C is D_ Sometimes _when A is B, C is not d_ E._If A is B, C is not D_ _If A is B, C is d_ O.Sometimes _when A is B, C is not D_ Sometimes _when A is B, C is d_ CONVERSE.

CONTRAPOSITIVE.
Sometimes _when C is D, A is B_ _If C is d, A is not B_ Sometimes _when C is D, A is B_ (none) _If C is D, A is not B_ Sometimes _when C is d, A is B_ (none) Sometimes _when C is d, A is B_ As to Disjunctives, the attempt to put them through these different forms immediately destroys their disjunctive character.

Still, given any proposition in the form _A is either B or C_, we can state the propositions that give the sense of obversion, conversion, etc., thus: DATUM .-- _A is either B or C;_ OBVERSE .-- _A is not both b and c;_ CONVERSE .-- _Something, either B or C, is A;_ CONTRAPOSITIVE .-- _Nothing that is both b and c is A_.
For a Disjunctive in I., of course, there is no Contrapositive.