Eternity (or forever) is endless time. In philosophy and mathematics, an infinite duration is also called sempiternity, or everlasting. Eternity is an important concept in many religions, where the immortality of God is said to endure eternally. Some, such as Aristotle, would say the same about the natural cosmos in regard to both past and future eternal duration, and like the eternal Platonic Forms, immutability was considered essential.
The metaphysics of eternity studies that which necessarily exists “outside” or independently of space and time. Another important question is whether “information” or Form is separable from mind and matter. Aristotle established a distinction between actual infinity and a potentially infinite count: a future span of time must be a potential infinity, because another element can always be added to a series that is inexhaustible.