Few philosophers or theologians exerted as much influence on the shape of medieval thought as Thomas Aquinas. He ranks amongst the most famous of the Western philosophers and was responsible for almost single-handedly bringing the philosophy of Aristotle into harmony with Christianity. He was also one of the first philosophers to argue that philosophy and theology could support each other. The shape of metaphysics, theology, and Aristotelian thought today still bears the imprint of Aquinas' work. In this extensive and deeply researched study, Eleonore Stump examines Aquinas' major works, Summa Theologiae and Summa Contra Gentiles, and clearly assesses the vast range of Aquinas' thought. Philosophers, theologians, and students of the medieval period alike will find this unrivalled study an indispensable resource in researching and teaching Aquinas.