- Eternal links here. For the British pop band, see Eternal (band).
- For Eternals, the Marvel comic book characters created by Jack Kirby, see Eternals.
- For the £1,000,000 prize geometric puzzle, see eternity puzzle.
While in the popular mind, eternal often simply means existing for an infinite, i.e., limitless, amount of time, many have used it to refer to a timeless existence altogether outside of time. There are a number of arguments for eternity, by which proponents of the concept, principally, Aristotle, purported to prove that matter, motion, and time must have existed eternally.
Eternity as a timeless existence
Augustine of Hippo wrote that time exists only within the created universe, so that God exists outside of time; for God there is no past or future, but only an eternal present. That position is accepted by many believers. And one need not believe in God in order to hold this concept of eternity: an atheist mathematician can maintain the philosophical tenet that numbers and the relationships among them exist outside of time, and so are in that sense eternal.
Near-death experience testimonies typically speak of eternity as a timeless existence by stating that portions of experiences in the eternal world lasted, say, "an hour or a month, I don't know. There was no time."
God and eternity
Theists say that God is eternally existent. How this is understood depends on which definition of eternity is used. On the one hand, God may exist in eternity, a timeless existence where categories of past, present, and future just do not apply. On the other hand, God may exist for or through eternity, or at all times, having already existed for an infinite amount of time and being expected to continue to exist for an infinite amount of time.
Whichever definition of eternity is understood, it is common to observe that finite human beings cannot fully understand eternity, since it is either an infinite amount of the time we know or something other than the time and space we know. But for the infinite definition, there are parallels that give some notion of an infinity--of at least a potential infinity, or a series that begins and has not ended. A series of moments that has begun and not ended is potentially eternal by that definition.
Related to the notion of eternal existence is the concept of God as Creator, as a being completely independent of "everything else" that exists because he created everything else. (Contrast this with panentheism.) If this premise is true, than it follows that God is independent of both space and time, since these are properties of the universe. So according to this notion, God exists before time began, exists during all moments in time, and would continue to exist if somehow the universe and time itself were to cease to exist.
Related to the Mankind, the biblical revelation first indicated that Man as a special created being is able to grasp the abstract form in contrast with the lower animal world which did not have the ability to understand the concept of "eternity". See book of Ecclesiastes 3::11 "He has made everything beautiful in its time. He has also set eternity in the hearts of men ..". from Bible translation in the N.I.V
See also the nature of God in monotheistic religions.
Afterlife is often believed to be eternal.
Science and eternity
The modern theory of relativity provides a physical description of the universe in which the past and future may exist alongside the present. Some scientific theories of consciousness such as space-time theories of consciousness propose that the space-time continuum permits consciousness.
The physics taught in most schools describes the universe in terms of Galilean relativity in which only the durationless present exists. This concept is known as presentism and is widely believed although questionable.
Symbolism and eternity
Eternity is often symbolized by the image of a snake swallowing its own tail, known as Ouroboros (or Uroboros), though the symbol can also carry a number of other connotations.
The circle is also commonly used as a symbol for eternity. The related concept, infinity, is symbolized by .
steady-state universe, presentism, eternal return, pantheism