— 443 —
The nominal essence bounds the Species.       §7. The next thing to be considered is, by which of those Essen-
ces it is, that Substances are determined into Sorts, or Species; and that
’tis evident, is by the nominal Essence. For ’tis that alone, that the
name, which is the mark of the Sort, signifies. ’Tis impossible
therefore, that any thing should determine the Sorts of Things,
which we rank under general Names, but that Idea, which that
Name is design’d as a mark for; which is that, as has been shewn,
which we call the Nominal Essence. Why do we say, This is a Horse,
and that a Mule; this is an Animal, that an Herb? How comes any
particular Thing to be of this or that Sort, but because it has that
nominal Essence, Or, which is all one, agrees to that abstract Idea,
that name is annexed to? And I desire any one but to reflect on his
own Thoughts, when he hears or speaks any of those, or other
Names of Substances, to know what sort of Essences they stand for.
Locke Hum III, 6, §7, p. 443