  Proclus discusses eternity and time in his commentary on the Timaeus and in propositions 53–55 of the Elements of Theology (see Steel 2001). Aristotle had defined time as a “measure of movement according to the before and after.” Therefore, anything measured by time must have a form of existence or activity in which a past and a future state can be distinguished. In fact, an entity in time is never wholly and simultaneously what it is, but has an existence extended in a process of before and after. Opposed to it stands the eternal, which exists as a simultaneous whole and admits of no composition or change. “There is no part of it,” writes Proclus, “which has already subsisted and another that will subsist later, but as yet is not. All that it is capable of being, already possesses it in entirety without losing it or without accumulating” (Elem. Theol. § 52). One must distinguish the temporality of things in process from the time by which they are measured. Temporal things participate in time, without being time. “Time exists prior to all things in time” (Elem. Theol. § 53). 