The idea of the eternal recurrence is that we will live the exact same lives again an infinite number of times. Nietzsche appreciates that this would multiply the value of a single life by infinity, justifying intense emotional responses. His unpublished notes provide a cosmological argument for the eternal recurrence that anticipates Poincaré's recurrence theorem. Nietzsche's Thus Spoke Zarathustra describes its hero discovering this idea and struggling to accept the recurrence of all bad things. He eventually comes to love the eternal recurrence because it will bring back all the joys of his life, and teaches this idea to others.
