Chapter 2 examines the reception of Aristotle’s action theory from the 1220s to 1277 and its influence on novel theories of free will developed in this period. It shows that the reception of Aristotle led to a “psychological turn”: instead of assuming the existence of free will, theologians began to argue for it by clarifying the nature of intellect and will, in which free will is grounded. The chapter canvasses the theories of free will in broad strokes from William of Auxerre to Bonaventure, and in more detail regarding Thomas Aquinas and Siger of Brabant, whose views will provoke strong reactions. Following Aristotle closely, Aquinas understands choices as determined by the practical deliberation that precedes them; one chooses as one judges worth choosing, and one can choose otherwise only because deliberation allows one to judge otherwise. Appealing to the authority of Avicenna, Siger argues that what causes the will’s acts does so necessarily.