Ed Siecinski examines how the Church has viewed the procession of the Holy Spirit throughout its history, beginning with the Trinitarian controversies of the early Christian centuries. The first comprehensive study of the key controversy separating the Eastern and Western churches.

"The tragic schism between Eastern Orthodoxy and Western Christianity has for more than a millennium centered on the doctrine of the procession of the Holy Spirit within the Trinity, whether the Spirit proceeds from the Father, or from the Father and the Son (Filioque), and in particular on the Western addition of the phrase Filioque to the creed. It is a long and tangled controversy which is traced in all its twists and turns with admirable clarity by Edward Siecienski in this fine book. Siecienski explores the past and looks to the future. One of his more astonishing revelations is that it is one of the earliest attempts at an irenical approach to the question-by the seventh-century monk and theologian, St Maximus the Confessor-that holds out the best hopes in the present for a final resolution of this controversy." --Andrew Louth, Author of Greek East and Latin West: the Church ad 681-1071 "At last we have the history of the Filioque controversy from beginning to end, free of confessional bias, engaging with both the theology and the historical context. An admirable presentation of the blend of Trinitarian theology, ecclesiastical rivalry, and historical events that sustained (and sometimes still sustain) the controversy, Siecienski's book should be required reading for interested historians, theologians, and ecumenists. I have wanted this book for a long time and am thrilled to have it on my desk at last." --Tia Kolbaba, Author of Inventing Latin Heretics: Byzantines and the Filioque in the Ninth Century "Siecienski excavates the intricacies of the Filioque controversy with magisterial ability in this excellent study. He is equally adept in telling us why the argument arose, and why it still matters. This is a book that is bound to become an authoritative classic on the subject." --John A. McGuckin, Author of The Orthodox Church: Its History and Spiritual Culture "This is a hugely accessible, up-to-date survey of the field free of the fog of polemic and bias."--Aristeides Papadakis, University of Maryland-Baltimore County "He writes gracefully and is remarkably free of the bias that plagues most of the literature devoted to the filioque. We are in his debt."--IRober M. Haddad, Smith College "...I heartily recommend this volume to anyone who has been touched by the issues surrounding the filioque, which in truth should be all Christians."--Nick Norelli "...the work will likely established itself as the best English introduction to the topic."--John T. Slotemaker "Beacause of th eclarity and brevity of its methodology and textual analysis, The Filioque is destined to become a classic on the subject for decades to come."--Bradley Nassif, Church History "Edward Siecienski has written a valuable history of the doctrinal controversy of the filioque, the Western addition to the Creed of Constantinople I (381) meaning that the Holy Spirit proceeds from the Father and the Son. Siecienski says that his book "is, first and foremost, a theological work" (vii). He gives not merely a review of the evidence from one of the longest and most complicated disputes in Christian history, but an explicit theological interpretation that will illuminate and challenge a spectrum of interested readers."--The Thomist