Thomas Wylton's Quaestio de anima intellectiva is one of the most significant medieval treatments of the intellectual soul. This edition of the Latin text is accompanied by an en face English translation by Gail Trimble. The detailed introduction guides the reader through the intricacies ofthe transmission of the text as well as its philosophical contents. Wylton's Quaestio presents a strong and controversial defence of Averroes' interpretation of Aristotelian psychology. In his comparison of Averroes' view with the Catholic doctrine of the human soul, as defined by the Council of Vienne, Wylton highlights the rationality of the Arabic philosopher'sstance and raises strong arguments against the commonly accepted opinion of Catholic thinkers, such as Thomas Aquinas and his followers. Wylton's Quaestio had a strong influence on his contemporaries and in particular on the most eminent exponent of Latin Averroism, John of Jandun, who included longpassages from Wylton's treatise in his commentary on Aristotle's On the Soul. Wylton also addresses fundamental philosophical issues: the ontological status of a subsisting form, the existence of universal things as components of individuals, and the possibility of intellectual knowledge of universals as well as singulars. This combination of polemics and engagingphilosophical reflection is one of the distinguishing features of Wylton's text and makes his work of significance to historians, philosophers, and theologians.