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

AND THE ARISTOTELIAN SYLLOGISM. 139
(a) The major premise must be universal.
(b) The minor premise must be affirmative. These
are called the special rules or canons of the first figure,
to distinguish them from the general rules ( 4) which
are applicable to all the figures.
The usual statement of the Aristotelian canon is
called the dictum de omni et de nullo. It has come
down to us from the mediaeval logicians :
1 Whatever
is predicated, affirmatively or negatively, of a whole
class, must be predicated, affirmatively or negatively,
of everything contained under that class. The affir
mative predication of the class is de omni, the negative
de nullo. The application of this to the rules of the
first figure is obvious. The major premise makes a
statement about a whole class, so that it must be
universal, and may be negative ;
the minor asserts that
a given case comes under that class, so that it must
be affirmative ; and, in accordance with the dictum,
the conclusion makes the original statement of the
given case.
The first figure is of the greatest importance both in
science and practical life. Whenever we apply previous
knowledge to a given case, we employ one of the moods
of this figure, although no syllogism and even no
distinct propositions may be before our minds. Some
times even an ordinary "judgment of perception," or
recognition of an object, may be analysed in this form.
The minor premise being our perception of the general
qualities of the particular fact, may be placed first.
1 Aristotle did not state it in terms of the
"
"
class view of pro
positions : 6TO.V tTepov Kad erepou KaTTiyoprJTai ws Ka6 uTro/cei/xeVou,
tt&a Kara TOV KaT7]yopovfj.evov Aeyercu, irdvTa Kal Kara TOV vTroKi/j.ei>ov
p7/07)(reTcu (Cat., 3) i.e., whatever is said of the Predicate is said
of the Subject.