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

132
MEDIATE INFERENCE
one premise and predicate of the other; the general
form is
M P,
S M
We leave the quantity and quality of the propositions
undetermined, as we have only to indicate the position
of M as compared with that of S and P. In this
arrangement of the terms, M has a middle position : this
appears more clearly when the premises
are written as
Aristotle usually writes them, "P is predicated of M is predicated of S." This was Aristotle s reason
M,
for
the
" name middle term." All the syllogisms given in
2 of this chapter are of the first figure.
In the second figure the middle term is predicate in
both premises :
P M,
S M;
In the third figure the middle term is subject in both
premises :
M P,
M S;
.-. S P7
This was Aristotle s principle of division, and is very
simple : in fig. i. M is middle (its proper position)
in ;
fig. ii. it is predicate in both premises ; in fig. iii. subject
in both. Aristotle did not require to make a distinction
between the major and minor premises. This distinc
tion was made by later logicians, and was taken to be
of great importance by the mediaeval writers on the
subject. Hence Aristotle s first figure was divided into
two parts, one of which was afterwards made into a