The Gay Science (German: Die fröhliche Wissenschaft) or The Joyous Wisdom is a book by Friedrich Nietzsche, first published in 1882 and followed by a second edition, which was published after the completion of Thus Spoke Zarathustra and Beyond Good and Evil, in 1887. This substantial expansion includes a fifth book and an appendix of songs. It was noted by Nietzsche to be "the most personal of all [his] books", and contains the greatest number of poems in any of his published works. In The Gay Science, Nietzsche experiments with the notion of power but does not advance any systematic theory. The book contains Nietzsche's first consideration of the idea of the eternal recurrence, a concept which would become critical in his next work Thus Spoke Zarathustra and underpins much of the later works. 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.'