Generations of scholars have observed that the aspectus/affectus distinction was a signature feature in the thought of Robert Grosseteste. This division of the rational soul's powers into the cognitive and the appetitive appears frequently in the English polymath's works across genres and through at least four decades of his scholarly career. The work contained in this volume presents the first full historical and systematic analysis of Grosseteste's aspectus/affectus distinction and finds that this distinction is an important key to understanding a web of interrelated themes in Grosseteste's thought. The doctrines accompanying aspectus and affectus are fundamental to his psychology and have important connections to his metaphysics, soteriology, mystical theology, and epistemology. Because Grosseteste's aspectus/affectus distinction unites multiple areas of his thought, this work serves a secondary function as the most recent introduction to Grosseteste's theology and philosophy. While in no way replacing earlier studies by McEvoy and Ginther, this book advances the study of Robert Grosseteste in several areas, including his doctrine of the soul and his theory of illumination.