  To understand Locke’s notion of scientia, we must consider its objects: real essences and the necessary connections that flow from them. Denying the Aristotelian view that a single essence both grounds the properties of a thing, making it what it is, and provides the basis for classifying it, Locke draws a distinction between real and nominal  essences.[12] Whereas the nominal essence consists in the set of observable qualities we use to classify a thing (which implies that the nominal essence could vary across time or communities), the real essence (or real or internal constitution, as Locke sometimes writes) is that which makes a thing what it is.