Eternal return or sometimes eternal recurrence is an esoteric concept originating from ancient Egypt and developed in the teachings of Pythagoras. The basic theory is that time is infinite, but there are a finite amount of actions in the universe, so all events will recur again and again infinitely. A large part of eternal recurrence is the idea that there is no final state of the universe, the universe merely cycles through the same states of matter and time with no destination. Time is perceived as circular and cyclical rather than the Western notion of a straight linear direction as developed by Aristotle and Judeo-Christian doctrine.

The symbol of the Ouroboros, the snake or dragon devouring its own tail is the alchemical symbol par excellence of eternal recurrence. The alchemist-physicians of the Renaissance and Reformation were aware of the idea of eternal recurrence; an attempt to describe eternal reccurence was made by the physician-philosopher Sir Thomas Browne in his Religio Medici of 1643:

And in this sense, I say, the world was before the Creation, and at an end before it had a beginning; and thus was I dead before I was alive, though my grave be England, my dying place was Paradise, and Eve miscarried of me before she conceived of Cain. (R.M.Part 1:59)

The idea of eternal recurrence is prominent in the writings of Friedrich Nietzsche. Nietzsche first encountered the idea in the works of Heinrich Heine, who speculated that there would one day be a person born with the same thought processes as himself, and that the same was true of every other person on the planet. Nietzsche expanded on this thought to form his theory, which he put forth in The Gay Science and developed in Thus Spoke Zarathustra.

On a few occasions in his notebooks, Nietzsche discusses the possibility of the Eternal Recurrence as cosmological truth, but in the works he prepared for publication, it is treated as the ultimate method of life affirmation. According to Nietzsche, it would require a sincere Amor Fati (Love of Fate), not simply to endure, but to wish for the eternal recurrence of all events exactly as they occurred---all of the pain and joy and the embarrassment and glory.

Nietzsche calls the idea "horrifying and paralyzing", and he also states that the burden of this idea is the "greatest weight" imaginable (das schwerste Gewicht). The wish for the eternal return of all events would mark the ultimate affirmation of life:

What, if some day or night a demon were to steal after you into your loneliest loneliness and say to you: 'This life as you now live it and have lived it, you will have to live once more and innumerable times more' ... Would you not throw yourself down and gnash your teeth and curse the demon who spoke thus? Or have you once experienced a tremendous moment when you would have answered him: 'You are a god and never have I heard anything more divine.' (The Gay Science )

As described by Nietzsche, the eternal return is more than just an intellectual concept or challenge, it is akin to a koan, or a psychological device that occupies one's entire consciousness stimulating a transformation of consciousness known as metanoia.

In modern times eternal recurrence was a major theme in the teachings of the Russian mystics Gurdjieff and P. D. Ouspensky whose novel Strange tale of Ivan Osokin (first published St. Petersburg 1915) illustrated that even given free-will to alter events in one's life the same events will occur regardless, to the individual.

References in art and literature

• James Joyce's novel Finnegans Wake, is based on the idea of eternal return. The novel begins in mid-sentence, with the continuation of the book's unfinished final sentence, creating a circle whereby the novel has no true beginning or end. [1]

• Joyce was influenced by Giambattista Vico (1668-1744), an Italian philosopher who proposed a theory of cyclical history in his major work, New Science. Joyce puns on his name many times in Finnegans Wake, including the "first" sentence: "by a commodius vicus of recirculation". Vico's theory involves the recurrence of three stages of history: the age of gods, the age of heroes, and the age of humans---after which the cycle repeats itself.

• Milan Kundera's novel The Unbearable Lightness of Being frequently references the concept of eternal return. Even the title comes from the fact that a person, in being, has a terrible lightness, and moves through the world with no weight or consequence to their actions in the grand scheme of things.

• The 2001 film K-PAX explains eternal return at the end.

• The film Groundhog Day is based upon the concept of eternal return. Its director Harold Ramis claimed of the novel The Strange Life of Ivan Osokin , the exemplary work upon eternal return that:

While not the original inspiration for our film Groundhog Day, was one of those confirming cosmic affirmations that we had indeed tapped into one of the great universal problems of being... P. D. Ouspensky suggests the antidote to the existential dilemma at the core of Groundhog Day: that trapped as we are on the karmic wheel of cause and effect, our only means of escape is to assume responsibility for our own destiny and find the personal meaning that imparts a purposeful vitality to life and frees us from the limitations of our contempt.

• The religious scholar Mircea Eliade has written of the theme of the eternal return as expressed in the world's religions.

• The philosopher Albert Camus discusses the plight of Sisyphus as an example of living the eternal return with a spirit of affirmation in his famous essay The Myth of Sisyphus.

Other notable films which debate the concept of eternal return include Terry Gilliam's Twelve Monkeys and Vanilla Sky.