Joseph Tixeront's A Handbook of Patrology is a comprehensive guide to the Church Fathers and ancient ecclesiastical writers. It examines figures who lived in early Christianity, emphasizing four main criteria: doctrinal orthodoxy, sanctity of life, ecclesiastical agreement, and antiquity, and includes important authors such as Tertullian and Origen. Tixeront explains that the title Father of the Church was originally given to bishops in the 2nd century and was commonly used by the 5th century to refer to ancient ecclesiastical writers. In addition to the Church Fathers who meet these criteria, the book also discusses other authors such as Tertullian, Origen, Eusebius of Caesarea, and Faustus of Riez, whose works, despite their doctrinal errors, are still considered valuable and important in Church history. It is a classic reference for understanding patristics (the study of the Church Fathers) in a structured way.