Eusebius of Caesarea believed in a somewhat idiosyncratic interpretation of the history of the world before the birth of Christ and the foundation of the Christian Church. He held that Christianity was not a new religion at all: on the contrary, it was the primordial, authentic religion of the human race, identical with the religion of the patriarchs of Genesis, so that the ancient Hebrews were Christians in all but name. According to Eusebius, all the traditional religions of mankind which existed in the Roman empire of his day were degenerate offshoots of the religion of the patriarchs – polytheism (to use the term which Philo of Alexandria invented: Eusebius always calls it polytheos planē) no less than Judaism, which had been introduced by Moses. Eusebius developed this pseudo-historical thesis in his enormous double work, the Praeparatio evangelica in fifteen books and the Demonstratio evangelica in twenty (of which the last ten are largely lost). Aaron Johnson sets the sustained polemic of the Praeparatio in the tradition of Greek and Jewish assertions of cultural identity by analysing its representations of ethnicity. His book easily establishes a strong claim to be regarded as the best introduction to Eusebius' massive work now available in any language. For Johnson knows recent discussions of the concept of ‘ethnicity,’ which he puts to good use, and he brings out the logical shape and coherence of Eusebius' overall argument that Greek civilisation and culture were heavily indebted to the Phoenicians, Egyptians and Hebrews. On the other hand, he fails to set Eusebius' work in its precise intellectual context of the second decade of the fourth century. He rejects Thomas Hägg's proof that the Contra Hieroclem transmitted under the name of Eusebius of Caesarea was in fact written by a homonym in north-west Asia Minor. Johnson misstates what is at issue: it is not a question of ‘authenticity’ which requires ‘further stylistic analysis’ (p. 165 n. 60), but of the correct attribution of a work which was without doubt written by a man called Eusebius c. 303, and Hägg's strongest argument comes not from the style of the pamphlet, but from its references to Hierocles's official position in the imperial administration. The question of authorship is important because, unlike any of the indubitable writings of Eusebius of Caesarea, the Contra Hieroclem has affinities to the Second Sophistic movement. Similarly, Johnson has failed to profit from recent work on Porphyry. He overlooks the relevance of Brian Croke's proof that Porphyry never wrote a Chronicle, although such a work occupies some seventeen pages in Felix Jacoby's classic collection of the fragments of the Greek historians (FGrH 260 fr. 1–3, 31–2). If Porphyry never wrote a Chronicle, then the fragments ascribed to it by Jacoby must in fact come from his Against the Christians, which, like the Praeparatio evangelica, was in fifteen books. Johnson could have enhanced the value of his work by including some substantive discussion, however brief, of what we know about the main specific target of Eusebius' polemic.