This new translation of Thomas Aquinas’s most important study of Aristotle casts bright light on the thinking of both philosophers. Using a new text of Aquinas’s original Latin commentary (Rene-Antoine Gauthier’s Leonine edition of 1984), Robert Pasnau provides a precise translation that will enable students to undertake close philosophical readings. He includes an introduction and notes to set context and clarify difficult points as well as a translation of the medieval Latin version of Aristotle’s De anima (On the Soul) so that readers can refer to the text Aquinas had at hand.