What is it that determines the identity of an entity? Processualism is a theoretical perspective that offers a startling answer to this question. The identity of an entity—whether human or nonhuman, animate or inanimate—depends on the set of relations in which this entity is located. And as the sets of relations are several, so are the identities that an entity can take. This article discusses this conclusion by integrating processual accounts from different fields of inquiry, such as relativistic physics and (...) actor-network theory. According to a processual interpretation of relativistic physics, speaking of states of things is but an abstraction. For states come from the introduction of arbitrary breakups of the spacetime continuum. Therefore, processes precede states, a process being a set of relations that confers identity on a physical state. According to a processual interpretation of actor-network theory, the same holds true for actors. Again, speaking of states of actors is but an abstraction. For what really acts is heterogeneous networks. When one describes actors in isolation, one is neglecting a whole array of relations with other actors whereby that actor can act or is made to act in such and such a way. These strands of processualism come to the same conclusion as to the identity of entities. These are not characterized by individuality but by individuality: they can be differently individuated according to the set of relations one is able to take into account. The main methodological consequence is that, if one intends to describe what an entity is, knowledge of this entity—whether human or nonhuman, animate or inanimate—should be based on progressively less narrow localizations and mappings of the relations it has to other entities. (shrink)