coeternal

Coeternal is an adjective used in philosophy, theology, and related disciplines to describe a shared temporal origin or duration of existence between two or more entities. Derived from co- meaning together and eternal, the term signals that the entities began to exist at the same time or have been in existence over the same span of time.

In metaphysical debates about God and the cosmos, coeternal is used to describe positions in which God and the universe are said to have a common beginning or to have existed for the same duration since their inception. Some classical theologies maintain that creation ex nihilo implies a non-coeternal universe; others, including certain ancient and modern philosophers, argued that the cosmos is coeternal with the divine.

In ordinary discourse, talk of coeternality is often connected to contemporaneity, but coeternal emphasizes a shared origin rather than merely existing at the same time. Coeternal should be distinguished from coeval, which stresses the age of beings rather than their exact starting point; and from eternal, which denotes infinitude rather than a shared temporal origin.