Fr. Aidan Nichols, O.P., of Blackfriars, Cambridge, is a lecturer in Cambridge University and a most prolific writer of theology in the English language. He has published on countless topics, especially in systematic, sacramental, and ecumenical theology, and was awarded the title Sacrae Theologiae Magister by the Dominican order in 2003. His books include important studies of St. Thomas Aquinas; modern thinkers, including Hans Urs von Balthasar; and the theology of Pope Benedict XVI. He has written on the liturgical“reform of the reform” and on “re-energising the Church in Culture,” as well as on the arts and iconography. The present book is based on a series of lectures given as the John Paul II Memorial Lecturer at the University of Oxford — the first Catholic Lectureship created in the university since the Reformation.