hich
are all legitimate and (2) that although _All A is B_ does not
distribute _B_ in relation to _A_, it does distribute _B_ in relation to
some _not-A_ (namely, in relation to whatever _not-A_ is _not-B_). This
is one reason why, in stating the rule in chap. vi. Sec. 6, I have
written: "an immediate inference ought to contain nothing that is not
contained, _or formally implied_, in the proposition from which it is
inferred"; and have maintained that every term formally implies its
contradictory within the _suppositio_.

Sec. 11. Immediate Inferences from Conditionals are those which
consist--(1) in changing a Disjunctive into a Hypothetical, or a
Hypothetical into a Disjunctive, or either into a Categorical; and (2)
in the relations of Opposition and the equivalences of Obversion,
Conversion, and secondary or compound processes, which we have already
examined in respect of Categoricals. As no new principles are involved,
it may suffice to exhibit some of the results.

We have already seen (chap. v. Sec. 4) how Disjunctives may be read as
Hypotheticals and Hypotheticals as Categoricals. And, as to Opposition,
if we recognise four forms of Hypothetical A. I. 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 _whe