Nietzsche was a manic-depressive. This is the conclusion that one doctor, Professor Jacques Rogé has come to after reading the works of the great philosopher, in particular his autobiographical texts. In light of this diagnosis, he explains why the author of Joyful Wisdom continuously oscillated between periods of creative exultation and periods of melancholic depression. In particular, he draws out the essential role that this illness played in the explosion of Nietzsche’s genius.