Eusebius, the church historian and Christian apologist, was bishop of Caesarea (Palestine) early in the fourth century. He is best known for his enthusiastic support of the emperor Constantine and for his pioneering Historia Ecclesiastica, intended to show how the church expanded but always remained the same because of its leaders' fidelity to tradition. Though Eusebius was essentially a historian rather than a philosopher, he did produce one work of significance for the history of philosophy. This is his Praeparatio Evangelica (Preparation for the Gospel), probably written between 312 and 318. It consists of fifteen books, perhaps because Porphyry's treatise, Kata Christianon (Against the Christians), contained the same number. Eusebius claimed that his treatise went beyond earlier works of controversy or exegesis; the novelty seems to have lain in the method of quoting passages in which philosophers contradict one another, although he obviously found materials for...