In the history of Christianity, the so-called 'Church Fathers' hold an immensely important place. This title, which we now associate with figures like St Augustine or St Jerome, was used from the fourth century onwards to designate particularly trustworthy authorities, whose opinions became the foundation of Western religious and intellectual culture. But who exactly were these Church Fathers? This examines this fundamental questions and considers which authors constituted the 'Church Fathers', the key religious authorities of the early Middle Ages, and assesses whether the Jewish historian Flavius Josephus formed part of this illustrious category. In the process Richard Matthew Pollard uses a variety of novel techniques: using new quantitative methods, as well as sensitive qualitative analysis, it sketches the shape of this shadowy group, and traces how certain figures join, or leave, this exclusive club. In particular, the book focuses on the place of Flavius Josephus, an ancient Jewish historian (c. 37-100) whom some have suggested became a quasi-Church Father. Only by carefully defining the Church Fathers can we evaluate such claims; in the process, we learn a great deal more about Josephus' understudied medieval legacy. Josephus and the Church Fathers in the Early Middle Ages ultimately enables us to understand and appreciate the foundational authorities of European Christian culture - some of whom were not Christian at all.