This book provides the best instruction on the most difficult issues that characterise St. Thomas Aquinas's Trinitarian theology. It explores the very purpose of Trinitarian theology, with an emphasis on distinguishing St. Thomas's approach from the various forms of arid rationalism and on displaying Aquinas's debt to Augustine's spiritual vision. The chapters on the Trinity engage the relationship of the Holy Spirit to the Son according to Aquinas - a topic treated in Trinity in Aquinas but now deepened by a meditation on ""the Spirit of Truth"" - as well as the ""personal mode"" of Trinitarian action ad extra. For readers seeking to understand how and why Aquinas's theology is fully Trinitarian rather than (as is sometimes suggested) modalist, Emery's exposition of the Trinitarian action ad extra and our relation in grace to each Person of the Trinity will be necessary reading. Fr. Emery devotes two chapters to the sacraments as they relate to the Church, in each case showing that Aquinas's insights speak profoundly to contemporary controversies. Another chapter treats briefly the place of the Eastern Fathers in Aquinas, a question that has become increasingly important in ecumenical dialogue so as to show that Thomistic theology is not antithetical to reunion with the Orthodox East. In the context of a world plagued by Cartesian dualism and inability to come to terms with the scope of human suffering, two further chapters treat Aquinas's hylomorphic understanding of the human person and his account of God's permission of evil (the latter through the lens of Charles Cardinal Journet). The book concludes on a fittingly ecumenical note, as Emery takes up George Lindbeck's influential reading of Aquinas as a ""postliberal"" theologian who thereby has an important place in contemporary Protestant-Catholic dialogue. In the hands of Gilles Emery, the work of Thomas Aquinas is shown to contribute profoundly to the task of appreciating and resolving the central theological discussions and controversies of our time.