The thesis that humanity progresses in a lawlike manner from inferior states (of wellbeing, cognitive skills, culture, etc.) to superior ones dominated eighteenth- and nineteenth- century thought, including authors otherwise as diverse as Kant and Ernst Haeckel. Positioning himself against this philosophically and scientifically popular view, Nietzsche suggests that humanity is in a prolonged state of decline. I argue that Nietzsche’s rejection of the thesis that progress is inevitable is a product of his acceptance of Lamarck’s use-and-disuse theory of evolution (...) and his belief that society selects for traits beneficial to society and negatively selects for traits that promote individual flourishing. This explains Nietzsche’s emphasis on self-development as cultivating traits that Nietzsche views as valuable and that would, by Lamarck’s theory of evolution, become heritable and so help steer our evolutionary trajectory, correcting our decline. (shrink)