 Although he assisted in early planning for Wagner’s Bayreuth project and attended the first festival, Nietzsche was not favorably impressed by the cultural atmosphere there, and his relationship with the Wagners soured after 1876. Nietzsche’s health, always fragile, forced him to take leave from Basel in 1876–77. He used the time to explore a broadly naturalistic critique of traditional morality and culture—an interest encouraged by his friendship with Paul Rée, who was with Nietzsche in Sorrento working on his Origin of Moral Sensations (see Janaway 2007: 74–89; Small 2005). Nietzsche’s research resulted in Human, All-too-human (1878), which introduced his readers to the corrosive attacks on conventional pieties for which he became famous, as well as to a style of writing in short, numbered paragraphs and pithy aphorisms to which he often returned in later work. When he sent the book to the Wagners early in 1878, it effectively ended their friendship: Nietzsche later wrote that his book and Wagner’s Parsifal libretto crossed in the mail “as if two swords had crossed” (EH III, HH, 5).