Nominal Essences of particular substances are undetermined by nature, and therefore various as men vary.
Wherein, then, would I gladly know, consist the precise and unmovable boundaries of that species?
It is plain, if we examine, there is no such thing made by Nature, and established by her amongst men.

The real essence of that or any other sort of substances, it is evident, we know not; and therefore are so undetermined in our nominal essences, which we make ourselves, that, if several men were to be asked concerning some oddly-shaped foetus, as soon as born, whether it were a man or no, it is past doubt one should meet with different answers.

Which could not happen, if the nominal essences, whereby we limit and distinguish the species of substances, were not made by man with some liberty; but were exactly copied from precise boundaries set by nature, whereby it distinguished all substances into certain species.

Who would undertake to resolve what species that monster was of which is mentioned by Licetus (lib.i.c.

3), with a man's head and hog's body?
Or those other which to the bodies of men had the heads of beasts, as dogs, horses, &c.
If any of these creatures had lived, and could have spoke, it would have increased the difficulty.