Scholars in the early seventeenth century who studied ancient Greek scientific theories often drew upon philology and history to reconstruct a more general picture of the Greek past. Gassendi’s training as a humanist historiographer enabled him to formulate a conception of the history of philosophy in which the rationality of scientific and philosophical inquiry depended on the historical justifications which he developed for his beliefs. Professor Joy examines this conception and analyzes the nature of Gassendi’s historical training, especially its relationship to his career as a physicist and astronomer. She shows how he rehabilitated Epicurean atomism by bringing together the arguments of the Greek atomists and those of his contemporaries. In doing so, he produced an account of the natural world which made it an object of empirical study and mechanical explanation.