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

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Porphyry explains the
THE PREDICABLES.
"
five . words," genus, species,
differentia, proprium, and accidens, as terms which are
used in Definition and Classification, and which it is
useful to understand. The mediaeval writers supposed
that he was giving a classification of possible predicates,
as such ; and great importance was attached to the list.
It was considered that every predicate-term must be
long to one of these five classes. The essentials of the
doctrine which was thus elaborated may be briefly
indicated.
Genus, species, and differentia, were defined as by
Aristotle. Proprium signified a property not given
in the definition of the term but following from it. It
may or may not be peculiar to the class which the
term denotes. Accidcns signified a property not fol
lowing from the definition and not necessarily con
nected with it. The accidens may be (a) inseparable,
as "the blackness of crows
"
; (b) separable.
As every genus must have at least two species under
it, and the species may again be genera to subordinate
species, wr e may arrange terms in a series according
to the decreasing extension of the concepts ; we may
begin with a genus which has no class above it, and
hence is called summum genus ; and we may end with
a species which cannot be further subdivided except
into individuals, and is
An example has been
therefore called
given (ch.
II.
infima species.
6). Such a
series of single terms is called a
"
predicamental line
"
(linea predicamentalis] ; and the intermediate classes,
between the highest and the lowest, are called subaltern
genera or species. The so-called
a device of later writers, is based on the
mental
"
series of concepts (see 9).
"
Tree of Porphyry,"
"
predica