Nietzsche wrote that he owed his philosophy to his long sickness, which he called “the teacher of great suspicion”. The present paper considers the related ideas of the will to power and the eternal return in the light of Nietzsche’s concepts of sickness and health. This reading of Nietzsche’s works is guided by the interpretations of Gilles Deleuze and Pierre Klossowski, whose commentaries have been most influential in shaping French neo-Nietzscheanism since 1965; however, those passages literally or metaphorically employing the (...) language of physical and mental illness and health are emphasized. After introducing the key concepts of will, force, affirmation, and self, the paper develops the idea of active and reactive forces, presents the eternal return as a selective doctrine, and considers the meaning of arnor fati. It closes with remarks, based upon Nietzsche’s views, on the interpretation of philosophical texts and on the relationship between the philosopher’s life and works. (shrink)