Thirdly, It ought to be determined whether those we call monsters be
really a distinct species, according to the scholastic notion of the
word species; since it is certain that everything that exists has its
particular constitution. And yet we find that some of these monstrous
productions have few or none of those qualities which are supposed to
result from, and accompany, the essence of that species from whence they
derive their originals, and to which, by their descent, they seem to
belong.


18. Men can have no ideas of Real Essences.

Fourthly, The real essences of those things which we distinguish into
species, and as so distinguished we name, ought to be known; i.e. we
ought to have ideas of them. But since we are ignorant in these four
points, the supposed real essences of things stand US not in stead for
the distinguishing substances into species.


19. Our Nominal Essences of Substances not perfect collections of the
properties that flow from the Real Essence.

Fifthly, The only imaginable help in this case would be, that, having
framed perfect complex ideas of the properties of things flowing from
their different real essences, we should thereby distinguish them into
species. But neither can this be done. For, being ignorant of the real
essence itself, it is impossible to know all those properties that flow
from it, and are so annexed to it, that any one of them being away, we
may certainly conclude that that essence is not there, and so the thing
is not of that species. We can never know what is the precise number of