It was then possible for him to deal with the doctrine of eternal recurrence as a mere philosophical speculation, without the uncomfortable reality of a demonstrated scientific fact, and thereafter he spent much time considering it. In "Also sprach Zarathustra" he puts it into the brain of his prophet-hero, and shows how it well-nigh drove the latter mad.
"I will come back," muses Zarathustra, "with this sun, with this earth, with this eagle, with this serpent--not for a new life or a better life, but to the same life I am now leading. I will come back unto this same old life, in the greatest things and in the smallest, in order to teach once more the eternal recurrence of all things."[2]