Patrology is usually defined as the study of the lives, doctrines, and writings of the Fathers of the Church. The Church, we learned as children, has four marks by which it may be known. Coincidentally there are four marks also by which a writer is recognized as a Father of the Church: a) orthodox doctrine, b) sanctity of life, c) antiquity, and d) approval of the Church. Antiquity is easily decided. The patristic age, by common agreement, ends in the West with the death of St. Isidore