This book contains the first English translations of The Origin of the Moral Sensations and Psychological Observations, the two most important works by the German philosopher Paul Ree. These essays present Rees moral philosophy, which influenced the ideas of his close friend Friedrich Nietzsche considerably. _x000B_Nietzsche scholars have often incorrectly attributed to him arguments and ideas that are Rees and have failed to detect responses to Rees works in Nietzsches writings. Rees thinking combined two strands: a pessimistic conception of human nature, presented in the French moralists aphoristic style that would become a mainstay of Nietzsches own writings, and a theory of morality derived from Darwins theory of natural selection. Rees moral Darwinism was a central factor prompting Nietzsche to write On the Genealogy of Morals and the groundwork for much of todays evolutionary ethics.?_x000B_In an illuminating critical introduction, Robin Small examines Rees life and work, locating his application of evolutionary concepts to morality within a broader history of Darwinism while exploring Rees theoretical and personal relationship with Nietzsche. In placing Nietzsche in his intellectual and social context, Small profoundly challenges the myth of Nietzsche as a solitary thinker.