Some temporal ontologies require a way of enforcing the temporal qualification of certain assertions—those about changing entities. In a knowledge representation language based on first–order logic, this is straightforwardly done by having a category of temporal regions and augmenting predicates with an additional argument place for the time at which a given predicate holds.

Here, I address the problem of representing entities changing over time and enforcing temporal qualification in first–order languages with predicates at most binary. It is possible, I argue, using temporal entities known as perdurants (events or processes)—towards which binary languages seem prima facie biased. There is however virtually no ontological cost for an ontology which in addition to changing entities recognizes changes, events and processes. Temporal knowledge representation therefore is not a lost cause even with languages with syntax and semantics limited to the representation of binary relations.