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

THE PREDICABLES. 1 67
similarly, the characteristics of being bounded by straight
lines, all in the same plane, belong to many other figures
beside "triangles." A difference, again, is a quality or
qualities distinguishing one kind of things
kinds of the same genus :
" Man
is rational."
"Triangles are three-sided"
from other
In the second case (/;) P is a o-vfjifieftrj/cos, usually
rendered accident, a quality which may or may not
belong to the subject ;
a century."
" some men live for upwards of
It will be found that every proposition must come
under one of these four heads. Most of the assertions
which we make in common life are cases of the so-called
"
accidental
"
predication.
2. We must now consider more fully these four
kinds of predication.
(a) Genus and Difference.
The concept which is poorer in defined qualities but
of wider extension is said to be the concept of a genus ;
while that which is richer in defined qualities, but nar
rower in extension, is called the concept of a species
(eZSo?). These terms are strictly correlative (ch. II.
3). The relation of species to genus is that of
subordination.
The simplest illustrations of generic and specific
concepts may be found in elementary plane geometry
e.g., "a triangle is a three-sided rectilineal figure." A
"rectilineal figure"
is a figure bounded by a certain
number (not yet defined) of straight lines. This is the
concept of a genus,
Aristotle s
lyez o?. It is a wider
group, including triangles, squares and other quadri
laterals, pentagons, &c. When we make the number