This volume provides an English translation of the papal encyclical "Fides et Ratio", considered to be one of the two or three most important and influential papal letters ever to have been written. This book also includes a commentary on the Letter by James McEvoy, and essays about the Letter's main themes by Roman Catholic and Greek Orthodox theologians. The latter evaluate the Letter's importance and show how it has shaped the modern study of philosophy and theology. This book provides the Latin text with accompanying English-language (facing page) translation. It should be of interest to: scholars and students of the philosophy of religion and of Roman Catholic doctrine; students of modern theology; Catholic clergy; and some educated lay people interested in dogmatics.