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

separate
AND THE ARISTOTELIAN SYLLOGISM. 133
"
fourth In this case we must dis
figure."
tinguish between the major and minor premises in
distinguishing the figures. In fig.
i. the middle term
is subject in the major premise and predicate in the
minor :
M P,
S M;
In fig. iv. the middle term is predicate in the major and
subject in the minor :
P.
P M,
M S;
It is not desirable in elementary Logic to depart from
the traditional recognition of the fourth as an inde
pendent figure.
Beside the division into four figures, syllogisms are
divided into classes according to the quantity and
quality of the premises. These classes are called
moods (inodi. rpoiroi TWV cr^Tj/jLaTcov). Now there
are two premises, and each premise must be A, E,
I, or O. Hence the greatest possible number of moods
will be the number of permutations 1 of these four
letters, two at a time. There are, in all, sixteen
such permutations :
AA EA IA OA
AE EE IE OE
AI El II OI
AO EO 10 00
In this table AA means, of course, that both premises
1 The name permutation is used in its strict mathematical
sense, according to which AE and EA, for example, are different
"
permutations."