Perichoresis (mutual indwelling) is a concept used extensively in the so-called Trinitarian revival; and yet no book-length study in English exists probing how the term actually developed in the ""classical period"" of Christian doctrine and how it was carefully deployed in relation to Christian dogma. Consequently, perichoresis is often used in imprecise and even careless ways. This path-breaking study aims at placing our understanding of the term on firmer footing, clarifying its actual usage in relation to doctrines of God, Christ, and salvation in the thought of John of Damascus, the eighth-century theologian, monk, and hymn writer who gave it its historically influential application. Since John summed up a whole theological tradition, this work provides not only an introduction to his theological vision but also to the key themes of Greek patristic thought generally and thereby lays an essential foundation for those who would dig deeper into the present-day usefulness of perichoresis. ""Those who have delved deep in the resources of patristic theology for the sake of theological renewal have long seen the concept of perichoresis as a vein of gold. But few have explored to sufficient degree the term's complexity and versatility. Twombly's book shows us how much potential treasure lies hidden by offering an extended meditation on the most fundamental structures of John Damascene's 'perichoretic theology.' His study is greatly to be welcomed and offers much to any student of early Christian thought."" --Lewis Ayres, Professor of Historical Theology, Durham University, Durham, UK ""I recently set out looking for a reliable guide to the concept of perichoresis in the thought of John of Damascus, only to discover with surprise and disappointment that such a book seemed not to exist. How could that be given the concept's popularity and John's undisputed importance in its shaping? I still have no answer to that question, so far as the past is concerned, but I am delighted to report that on this score the future is brighter. There is a sure-footed, intelligent, and thorough guide on this topic. You are holding it in your hands."" --Kendall Soulen, Professor of Systematic Theology, Wesley Theological Semimary, Washington D.C. ""Perichoresis is an inexhaustibly attractive idea, invoked in Trinitarian revivals, and essential, some believe, to an understanding of the divine fellowship for which we humans were made. In this wonderfully lucid study of John Damascene, Charles Twombly provides what is most needed to ground contemporary reflection: a discerning account of what perichoresis has historically meant, not only to this 'last of the Fathers' but to the cumulative tradition he bequeathed to Christendom, East and West."" --Carol Zaleski, Professor of World Religions, Smith College, Northampton, MA ""St. John Damascene famously said, 'I shall say nothing of my own,' and much modern scholarship has taken him at his word. Yet, as Charles Twombly shows, John Damascene was a truly original theologian. His notion of perichoresis, 'co-inherence,' though it has precedents in earlier Fathers, becomes in his theology a golden thread, drawing together his understanding of the Trinity, the incarnation, and our union with God, our deification. This lucid and profound study makes a major contribution to our understanding of John and his enduring significance."" --Andrew Louth, Professor emeritus of Patristic and Byzantine Studies, Durham University, Darlington, UK ""For a long time now, the looser sort of constructive theology has been afflicted with a bad case of 'galloping perichoresis,' and it has become trendy to say that just about anything mutually indwells just about anything else--perichoretically. This book recovers the witness of John of Damascus to help restore a great theological category to its proper place. Equal parts historical reconstruction and dogmatic clarification, Twombly's book celebrates the vast systematic scope of