n 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. Given a
Disjunctive in the form _Either A is B or C is D_, we may write for its
Obverse--_In no case is A b, and C at the same time d_. But no Converse
or Contrapositive of such a Disjunctive can be obtained, except by first
casting it into the hypothetical or categorical form.

The reader who wishes to pursue this subject further, will find it
elaborately treated in Dr. Keynes' _Formal Logic_, Part II.; to which
work the above chapter is indebted.

CHAPTER VIII

ORDER OF TERMS, EULER'S DIAGRAMS, LOGICAL EQUATIONS, EXISTENTIAL IMPORT
OF PROPOSITIONS

Sec. 1. Of the terms of a proposition which is the Subject and which the
Predicate? In most of the exemplary propositions cited by Logicians it
will be found that the subject is a substantive and the predicate an
adjective, as in _Men are mortal_. This is the relation of Substance and
Attribute which we saw (chap. i. Sec. 5) to be the central type of
relations of coinherence; and on this model other predications may be
formed in which the subject is not a substance, but is treated as if it
were, and could therefore be the ground of attributes; as _Fame is
treacherous, The weather is changeable_. But, in literature, sentences
in which the adjective comes first are not uncommon, as _Loud was the
applause, Dark is the fate of man, Blessed are the peacemakers_, and so
on. Here, then, 'loud,' 'dark' and 'blessed' occupy the place of the
logical subject. Are they really the subject, or must we alter the order
of such sentences into _The applause was loud_, etc.? If we do, and then
proceed to convert, we get _Loud was the applause_, or (more
scrupulously) _Some loud noise was the applause_. The last form, it is
true, gives the subject a substantive word, but 'applause' has becom