Thus Spake Zarathustra | Friedrich Nietzsche | Wordsworth World Literature | Book Thus Spake Zarathustra by Friedrich Nietzsche. This astonishing series of aphorisms, put into the mouth of the Persian sage Zarathustra, or Zoroaster, contains the kernel of Nietzsche's thought. 'God is dead', he tells us. Christianity is decadent, leading mankind into a slave morality concerned not with this life, but with the next. Nietzsche emphasizes the 'Ubermensch, or Superman, whose will to power makes him the creator of a new heroic mentality. The intensely felt ideas are expressed in prose-poetry of indefinable beauty.