Thus a circle is as essentially different from an oval as a sheep from a goat; and rain is as essentially different from snow as water from earth: that abstract idea which is the essence of one being impossible to be communicated to the other.

And thus any two abstract ideas, that in any part vary one from another, with two distinct names annexed to them, constitute two distinct sorts, or, if you please, SPECIES, as essentially different as any two of the most remote or opposite in the world.
15.

Several significations of the word Essence.
But since the essences of things are thought by some (and not without reason) to be wholly unknown, it may not be amiss to consider the several significations of the word ESSENCE.
Real essences.
First, Essence may be taken for the very being of anything, whereby it is what it is.

And thus the real internal, but generally (in substances) unknown constitution of things, whereon their discoverable qualities depend, may be called their essence.

This is the proper original signification of the word, as is evident from the formation of it; essential in its primary notation, signifying properly, being.