Fr. Thomas Crean, O.P., holds an S.T.L. from the Institut Saint-Thomas d'Aquin in Toulouse, France, and an S.T.D. from the International Theological Institute in Trumau, Austria. He has published in Augustinianum and New Blackfriars and is the author of several books, including St. Luke's Gospel: A Commentary for Believers (Arouca, 2021) and, with Alan Fimister, Integralism: A Manual of Political Philosophy (Editiones Scholasticae, 2020). He is a Fellow of the Dialogos Institute and the Albertus Magnus Center for Scholastic Studies and currently lives at St. Dominic's Priory, London.

• Acknowledgments ix Abbreviations xi Introduction 1 Part I The Procession of the Holy Spirit and the Fathers of the Church Chapter 1 The 1995 Statement on the Filioque: An Ambiguous Clarification 7 Chapter 2 Prolegomena to the Study of the Fathers 29 Chapter 3 St. Athanasius 43 Chapter 4 St. Hilary 61 Chapter 5 St. Basil the Great 83 Chapter 6 St. Epiphanius 103 Chapter 7 St. Gregory of Nazianzen 115 Chapter 8 St. Ambrose 131 Chapter 9 St. Gregory of Nyssa 143 Chapter 10 St. Augustine 167 Chapter 11 St. Cyril of Alexandria 185 Chapter 12 Roots of Anti-Filioquism in the Patristic Era 205 Chapter 13 St. Leo the Great 213 Chapter 14 St. Gregory the Great 217 Chapter 15 St. Maximus 227 Chapter 16 St. John Damascene 239 Chapter 17 Concluding Linguistic Remarks 253 Part I I The Theory of Ecumenical Councils Chapter 18 The Idea of an Ecumenical Council 263 Chapter 19 The Essence of Ecumenicity 277 Chapter 20 The Later Byzantine Theory 305 Chapter 21 Do Ecumenical Councils Need To Be “Received”? 337 Part I I I The Ecumenical Council of Ferrara-Florence Chapter 22 The Authority of the Council of Ferrara-Florence 363 Chapter 23 Denials of the Authority of the Council of Ferrara-Florence 389 Chapter 24 Postscript: Bessarion or Mark of Ephesus? 415 Appendix 1 The Florentine Definition of the Procession of the Holy Spirit 431 Appendix 2 Acts of Ecumenical Councils Approving by Name Certain Teachers of the Faith 433 Appendix 3 Patristic Testimonies Claimed by John de Montenero in Addressing the Council of Florence at the Seventh and Eighth Public Sessions in March 1439 (with Judgments on Authorship from Clavis Patrum Graecorum and Clavis Patrum Latinorum) 435 Appendix 4 Greek and Latin Traditions regarding the Procession of the Holy Spirit (by the Pontifical Council for Promoting Christian Unity) 439 Bibliography 453 index 469

Vindicating the Filioque gives much-needed clarity to the old dispute of the so-called 'Greek' and 'Latin' traditions regarding the procession of the Holy Spirit. Crean provides an engrossing analysis of a diverse range of Church Fathers on the topic, with a detailed analysis of Greek and Latin theological terms, showing how the teaching of the Fathers stands in relation to the Florentine definition. Examining the concept of ecumenicity embodied by the first seven councils, Crean shows how the Council of Florence meets any criteria accepted at the time by Greeks or Latins, vindicating the infallibility of its definitive teachings on matters of faith. As a Catholic priest of the Byzantine Rite, I consider this book to hold a special importance for rediscovering the theological heritage of the Eastern Catholic Churches and I recognize its important contribution to ecumenical dialogue. The good friar has offered us a clear exposition of 'fides orthodoxa' regarding the Procession of the Holy Spirit." - Rev. Dr. Yosyp Veresh Greek Catholic Eparchy of Mukachevo