An introductory text-book of logic - Mellone, Sydney - Rare Books at ...

148
MEDIATE INFERENCE
Fig. iii.
1. The minor premise must be affirmative.
2. The conclusion must be particular.
It is also possible to deduce every one of the General
Rules of the syllogism from the dictum de omni et de
nullo.
Aristotle called figs.
ii. and iii. the
"
imperfect
figures," as they have not the cogent and conclusive
character of fig.
i. They may be made independent
by constructing canons .or dicta applicable directly to
them, as the dictum of Aristotle is applicable to fig. i.
This has been done e.g., by Lambert (Ueberweg,
Logic, 103). But these maxims, it may be affirmed,
have not the clear, distinct, and self-evident character
of the Aristotelian dictum.
Aristotle himself exhibited the cogency of the moods
in the imperfect figures by means of the first figure.
The process is called Beduction ; and its general nature
may be stated thus : Transform the premises of the
imperfect syllogism in such a way that its conclusion
may be drawn from them in one of the valid moods of
the first figure. The transformation of the premises
is effected (a) by one of the processes of immediate
inference, applied to one or both of the premises,
(b) by transposition of the premises, if necessary, in
order to keep the major premise first.
The names given to the various moods in the im
perfect figures are not only the means of indicating,
by their three vowels, the quantity and quality of the
major premise, the minor, and the conclusion : some
of the intermediate consonants indicate the processes
by which reduction is effected. The significant con
sonants are s, /, m, and c ; and also the initial letters
of the names, B, C, D, F.