ach species is constituted (the _differentia_),
and other attributes, which belong to some or all of the individuals
but are not reckoned for purposes of division and definition
(_Propria_ and _Accidentia_). The list is not itself a logical
division: it is heterogeneous, not homogeneous; the two first are
names of classes, the three last of attributes. But corresponding to
it we might make a homogeneous division of attributes, as follows:--

Attributes
___________|____________
| |
Defining Non-defining
_____|______ ____|__________
| | | |
Generic Specific Proprium Accidens
(Differentia)

The origin of the title Predicables as applied to these five terms is
curious, and may be worth noting as an instance of the difficulty of
keeping names precise, and of the confusion arising from forgetting
the purpose of a name. Porphyry in his [Greek: eisagoge] or
Introduction explains the five words ([Greek: phonai]) simply as terms
that it is useful for various purposes to know, expressly mentioning
definition and division. But he casually remarks that Singular names,
"This man," "Socrates," can be predicated only of one individual,
whereas _Genera_, _Species_, _Differentiae_, etc., are predicables
of many. That is to say he describes them as Predicables simply by
contradistinction from Singular names. A name, however, was wanted for
the five terms taken all together, and since they are not a logical
division, but merely a list of terms used in dividing and defining,
there was no apt general designation for them such as would occur
spontaneously. Thus it became the custom to refer to them as
the Predicables, a means of reference to them collectively being
desiderated, while the meaning of this descriptive title was
forgotten.

To call the five divisional elements or _Divisoria_ Predicables is to
present them as a division of Predicate Terms on the basis of their
relation to the Subject Term: to suggest that every Predicate Term
must be either a Genus or a Species, or a Differentia, or a Proprium,
or an Accidens of the Subject Term. They are sometimes criticised
as such, and it is rightly pointed out that the Predicate is never a
species of or with reference to the Subject. But, in truth, the five
so-called Predicables were never meant as a division of predicates