 One can also explain the existence of the city-state in terms of the four causes. It is a kind of community (koinônia), that is, a collection of parts having some functions and interests in common (Pol. II.1.1261a18, III.1.1275b20). Hence, it is made up of parts, which Aristotle describes in various ways in different contexts: as households, or economic classes (e.g., the rich and the poor), or demes (i.e., local political units). But, ultimately, the city-state is composed of individual citizens (see III.1.1274a38–41), who, along with natural resources, are the “material” or “equipment” out of which the city-state is fashioned (see VII.14.1325b38–41).