this sense it is a singular term: but as applied to the various ways
in which the eye may be affected, it is evidently a common term, being
equally applicable to red, blue, green, and every other colour. As
soon as we begin to abstract from attributes, the higher notion
becomes a common term in reference to the lower. By a 'higher notion'
is meant one which is formed by a further process of abstraction. The
terms 'red,' 'blue,' 'green,' etc., are arrived at by abstraction from
physical objects; 'colour' is arrived at by abstraction from them, and
contains nothing, but what is common to all. It therefore applies in
the same sense to each, and is a common term in relation to them.

111. A practical test as to whether an abstract term, in any given
case, is being used as a singular or common term, is to try whether
the indefinite article or the sign of the plural can be attached to
it. The term 'number,' as the name of a single attribute of things,
admits of neither of these adjuncts: but to talk of 'a number' or 'the
numbers, two, three, four,' etc., at once marks it as a common
term. Similarly the term 'unity' denotes a single attribute, admitting
of no shades of distinction: but when a writer begins to speak of 'the
unities' he is evidently using the word for a class of things of some
kind or other, namely, certain dramatical proprieties of composition.



Proper _Names_ and _Designations_.


112. Singular terms may be subdivided into Proper Names and
Designations.