During his residence in Switzerland Nietzsche came to know a large circle of interesting people. He suffered, however, from extremely severe headaches, so frequent that they incapacitated him for about two hundred days in the year and brought him to the verge of the grave. In 1879 he resigned his professorship. From 1882 to 1888 his state of health improved, though extremely slowly. His eyes were still so weak that he was threatened with blindness. He was compelled to be extremely careful in his mode of life and to choose his place of residence in obedience to climatic and meteorological conditions. He usually spent the winter at Nice and the summer at Sils-Maria in the Upper Engadine. The years 1887 and 1888 were astonishingly rich in production; they saw the publication of the most remarkable works of widely different nature and the preparation of a whole series of new books. Then, at the close of the latter year, perhaps as the result of overstrain, a violent attack of mental disorder occurred, from which Nietzsche never recovered. As a thinker his starting-point is Schopenhauer; in his first books he is actually his disciple. But, after several years of silence, during which he passes through his first intellectual crisis, he reappears emancipated from all ties of discipleship. He then undergoes so powerful and rapid a development--less in his thought itself than in the courage to express his thoughts--that each succeeding book marks a fresh stage, until by degrees he concentrates himself upon a single fundamental question, the question of moral values. On his earliest appearance as a thinker he had already entered a protest, in opposition to David Strauss, against any moral interpretation of the nature of the Cosmos and assigned to our morality its place in the world of phenomena, now as semblance or error, now as artificial arrangement. And his literary activity reached its highest point in an investigation of the origin of the moral concepts, while it was his hope and intention to give to the world an exhaustive criticism of moral values, an examination of the value of these values (regarded as fixed once for all). The first book of his work, _The Transvaluation of all Values_, was completed when his malady declared itself. [1] "The expression 'aristocratic radicalism,' which you employ, is very good. It is, permit me to say, the cleverest thing I have yet read about myself,"--Nietzsche, Dec. 2, 1887. I.