 Locke begins “Of Identity and Diversity” by first getting clear on the principle of individuation, and by setting out what some have called the place-time-kind principle—which stipulates that no two things of the same kind can be in the same place at the same time, and no individual can be in two different places at the same time (L-N  2.27.1).[2]  With some of the basics of identity in place, Locke posits that before we can determine the persistence conditions for atoms, masses of matter, plants, animals, men, or persons, we must first know what we mean by these terms. In other words, before we can determine what makes atoms, masses of matter, plants, animals, men, or persons the same over time, we must pin down the nominal essences—or general ideas—for these kinds. Of this Locke says, 