In his richly documented and still valuable study of Aquinas and the Church Fathers, published in 1946, Gottfried Geenen, O.P. noted that the study of this aspect of Thomas Aquinas's thought was just beginning to take place. More than seventy years later considerable progress has been made, both historically and doctrinally, not at least due to the technological advances in the area of the study of Aquinas' writings. It has been argued both that Aquinas had a remarkable knowledge of a wide range of the Church Fathers and that he was actively engaged in acquiring new material from hitherto unknown Fathers. Due to Thomas' profound commitment to both Latin and Greek patristic sources he was not only able to draw on the rich tradition of the past but also explore new possibilities and solutions. This commitment and interaction between tradition and speculative reason has led some to claim tentatively that one might characterize Thomas Aquinas' theology as being ad mentem patrum. The goal of this volume is to explore ways to corroborate this claim. In order to do so, the contributions investigate the presence and use of the Church Fathers in Aquinas' thought both historically and systematically.