1. The Will to Eternal Recurrence. 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; and there will be nothing new in it, but every pain and every joy and every thought and sigh and everything unutterably small or great in your life will have to return to you, all in the same succession and sequence — even this spider and this moonlight between the trees and even this moment and I myself. The eternal hourglass of existence is turned upside down again and again, and you with it, speck of dust!"
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." — If this thought gained possession of you, it would change you as you are or perhaps crush you. The question in each and every thing, "Do you desire this once more and innumerable times more?" would lie upon your actions as the greatest weight. Or how well disposed would you have to become to yourself and to life to crave nothing more fervently than this ultimate eternal confirmation and seal? (Gay Science, 341)
2. Eternal Recurrence and Nihilism. Let us think this thought in its most terrible form: existence as it is, without meaning or aim, yet recurring inevitably without any finale of nothingness: the eternal. This is the most extreme form of nihilism: the nothing (the meaningless), eternally! The European form of Buddhism: the energy of knowledge and strength compels this belief. It is the most scientific of all possible hypotheses. We deny end goals: if existence had one it would have to have been reached. (Will to Power, 55)
3. Eternal Recurrence and Spinoza’s Pantheism.So one understands that an antithesis to pantheism is attempted here: for "everything perfect, divine, eternal" also compels a faith in the "eternal recurrence." — Question: does morality make impossible this pantheistic affirmation of all things too? At bottom, it is only the moral god that has been overcome. Does it make sense to conceive a god — beyond good and evil—? Would a pantheism in this sense be possible? Can we remove the idea of a goal from the process and then affirm the process in spite of this? This would be the case if something were attained at every moment within this process — and always the same. Spinoza reached such an affirmative position in so far as every moment has a logical necessity, and with his basic instinct, which was logical, he felt a sense of triumph that the world should be constituted that way. (Will to Power, 55)
4. Eternal Recurrence and the World Affirmation beyond All Pessimism. Whoever has endeavored with some enigmatic longing, as I have, to think pessimism through to its depths and to liberate it from the half-Christian, half-German narrowness and simplicity in which it has finally presented itself to our century, namely, in the form of Schopenhauer's philosophy; whoever has really, with an Asiatic and supra-Asiatic eye, looked into, down into the most world-denying of all possible ways of thinking -- beyond good and evil and no longer, like the Buddha and Schopenhauer, under the spell and delusion of morality -- may just thereby, without really meaning to do so, have opened his eyes to the opposite ideal: the ideal of the most high-spirited, alive, and world-affirming human being who has not only come to terms with whatever was and is, but who wants to have what was and is repeated into all eternity, shouting insatiably da capo -- not only to himself but at bottom to him who needs precisely this spectacle -- and who makes it necessary because again and again he needs himself -- and makes himself necessary. ---- What? And this wouldn't be -- circulus vitiosus deus? (Beyond Good and Evil, Section 56)