Constantine the Emperor
David Potter
OUP £25
(978-0-19-975586-8)
Church Times Bookshop £22.50 (Use code CT213 )

THIS is not a book for people who just want the story of Constantine the Christian Emperor. It is written by a professor of ancient history, not a theologian or a church historian.

And that makes it much more attractive for anyone who really wants to understand how the Roman Empire functioned, how the Church came to be absorbed into imperial structures and administration, and how the Emperor's aims and ideas developed as his experience of running (or at least heading) the empire grew.

Thus it takes 150 pages to reach the battle of the Milvian Bridge in AD 312, that iconic moment of change when Constantine gave his allegiance to the God of the Christians, apparently adopted the labarum as his emblem, and took his first great step towards obliteration of everyone who stood between him and supreme power (in this respect he remained pure Roman throughout his life). The text is supported by clear maps and illustrations.

Potter uses this detailed background on Diocletian, his reforms and establishment of the tetrarchy (the system of two senior and two junior emperors), to reveal the imperial milieu that formed the young Constantine. Emphasising history rather than theology allows him to look dispassionately at Constantine's actions in appropriating the novel mode of governance (by council; the Greek word is synodos) which he found operating in the Church.

He also gives Constantine fair credit for handling a tense situation of theological disagreement, showing how Constantine resorted to a tried and tested imperial method for imposing a rule: producing an authoritative text demanding universal allegiance within the empire. Instead of sneering at the Emperor for theological ignorance, he emphasises the originality of his scheme and the positive effects of his interventionin the council.

I did have some quibbles in matters of detail. The decision of Constantine and Licinius as joint Emperors in 313 to issue the so-called "edict of Milan" permitting equal treatment for all those who worshipped the gods is not, as Potter's overblown claim states, "a stunning assertion that freedom of thought is a good thing". It is a concession made in order to ensure that no gods are neglected.

Constantine at this time was only beginning to grasp the exclusive nature of Christianity (Potter uses Constantine's coinage, and the symbolism of his triumphal arch, to make this very point). The actual text (in Licinius's version) states that this right was a "concession for the sake of peace in our time" - a much less lofty claim.

I wonder, too, whether Potter is more familiar with Late Antiquity than the Republican Roman history; for he says of Diocletian that no one before him had ever voluntarily let go of the supreme power. But that is exactly what Dictator Sulla did in the first century BC - and, moreover, so notoriously that he became a subject for schoolboys to practise their speech-writing on.

The Revd Dr Cally Hammond is the Dean of Gonville and Caius College, Cambridge.