Eternity in common parlance means infinite time. In classical philosophy, however, it is defined as what exists outside time as describing supranatural beings and forces whereas sempiternity corresponds to the temporal, non-metaphoric definitions, as recited in requiem prayers for the dead. Thomas Hobbes and many others in the Age of Enlightenment drew on the classical distinction made to put forward metaphysical hypotheses such as "eternity is a permanent Now".
Eternity is an important concept in many religions, where the god or gods are 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. Today cosmologists, philosophers and others look to analyses of the concept from across cultures and history and debate, among other things, whether an absolute concept of eternity has real application such for the fundamental laws of physics such as the arrow of time in entropy.


1. Philosophy
Aristotle argued that the cosmos has no beginning. In Aristotles Metaphysics, eternity is the unmoved mover God, understood as the gradient of total synergy "produces motion by being loved". Boethius defined eternity as "simultaneously full and perfect possession of interminable life".

2. Symbolism
Eternity is often symbolized by the endless snake, swallowing its own tail, the ouroboros or oroboros. The circle, band or ring is also commonly used as a symbol for eternity, as is the mathematical symbol of infinity, ∞ {\displaystyle \infty }. Symbolically these are reminders that eternity has no beginning/end.