“The Book of the Holy Spirit, to Saint Amphilochius, Bishop of Iconium” is the second great theological work of St. Vasily. The reason for its writing has its own history, which makes it possible to accurately date this work and clarify the contemporary theological situation. During one liturgical meeting in Caesarea Cappadocia in honor of St. Martyr Eupsychius, i.e. September 7, 374, St. Vasily allowed himself to pronounce the doxological formula in different ways. Either he said, as the people were accustomed to this: “Glory to the Father, through the Son, in the Holy Spirit,” then “Glory to God the Father with the Son and the Holy Spirit.” This change in the usual doxological formula caused considerable confusion among believers. At that time, filled with intense struggle for the idea of the Holy Trinity and for its verbal expressions, the people were ready to see in any new expression an attack on dogmatic freedom, on religious inaccuracy, and, therefore, on the source of hidden false teaching. A friend of St. who was present at this service. Basil, St. Amphilochius turned to him with bewilderment and asked for appropriate clarification. St. Basil gave them in this treatise, which is called “The Book of the Holy Spirit.” This work was begun by writing immediately after September 7, 374 and was completed, as letter 231 testifies to us, at the end of the next year 375. Thus, it is one of the later creations of St. Basil, already a bishop, when he was therefore 46 years old. The book, apparently by the author himself, is divided into 30 chapters and, in addition, into 79 sections. Its significance is undoubtedly great, since, in addition to the previously mentioned four letters of St. Athanasius to Serapion and the works of Didymus the Blind on the Holy Spirit, this is one of the most important pneumatological works of Christian antiquity. For every Orthodox reader it is especially valuable both for the topic itself and for the thoughts expressed in it. Archimandrite Cyprian (Kern). (From the book “The Golden Age of Patristic Writing”)