The philosophy of Friedrich Nietzsche (1844-1900) was almost wholly neglected during his sane life, which ended abruptly in 1889. Since then he has been appropriated as an icon by an astonishingly diverse spectrum of people, whose interpretations of his thought range from the highly irrational to the firmly analytical. Thus Spake Zarathustra introduced the ubermensch, or "superman," and The Twilight of the Idols developed the notorious "will to power"...