Sergius Bulgakov is widely considered to be the twentieth century's foremost Orthodox theologian, and his book The Comforter is an utterly comprehensive and profound study of the Holy Spirit.

Encyclopedic in scope, The Comforter explores all aspects of the doctrine of the Holy Spirit, as they are viewed in the Orthodox tradition and throughout church history. The book has sections on the development of the doctrine of the Spirit in early Christianity and on the development of the doctrine of procession in the patristic and later Byzantine periods. It also touches on the place of the Holy Spirit in the Trinity and explores Old and New Testament notions of the Spirit of God. A concluding chapter deals with the mystical revelation of the Holy Spirit. Made available in English through the work of Boris Jakim, today's premier translator of Russian theology and philosophy into English, Bulgakov's Comforter in this edition is a major publishing event.