Robert Grosseteste (c. 1168-1253), Bishop of Lincoln from 1235 to 1253, was one of the most prominent and remarkable figures in thirteenth-century English intellectual life. He made a powerful impression on his contemporaries and subsequent thinkers at Oxford, and has been hailed as an inspiration to scientific developments in fourteenth-century Oxford. De libero arbitrio, his influential treatise on free will, was written between about 1225 and the early 1230s. This new edition contains Latin texts and en-face English translations of the two versions of the treatise. An extensive introduction provides a thorough account of Grosseteste's treatise, the sources of the text and also its uses in later writers such as Richard Rufus of Cornwall and Richard Fishacre. This book will be of interest not only to specialists in medieval philosophy and theology, but also to the general reader interested in free will. Acknowledgements Sigla and Abbreviations Introduction De libero arbitrio, earlier recension De libero arbitrio, later recension Appendix: Richard Rufus of Cornwall on the Problem of a Plurality of Eternal Beings Index Sacrae Scripturae Index Auctorum Operumque Antiquorum Index of Modern Works and Authors Index Doctrinalis Index to the Introduction After studying philosophy as an undergraduate in Australia, Neil Lewis did his PhD degree at Pittsburgh in the United States, developing an interest in medieval philosophy. His research has focused on Robert Grosseteste and early thirteenth-century English philosophy. He is a core member of the Ordered University Project devoted to interdisciplinary study of Grosseteste's scientific works, and also of the Richard Rufus of Cornwall Project, which is devoted to the preparation of critical editions of the works of Richard Rufus of Cornwall. Most of his academic career has been spent as a professor in the philosophy department at Georgetown University in Washington D.C.