Paul Veyne is well known for his opposition to all theories and all generalisations; according to him we live in a sub-lunar world where chance rules supreme and historians are wrong to attempt to discover causes. In this latest essay, superbly translated by Janet Lloyd, he seeks to understand the greatest revolution in the ancient world. Constantine was truly converted and believed that he had a divine mission to impose Christianity on his subjects; the reason for his actions was that he was rightly convinced that Christianity was (and still is) the best of all religions, with its teachings of humility, love and tolerance. Leaving aside the extreme version of intentionalism that Veyne imposes on his material, in its factual outlines this has been the general view of historians since at least the Second World War and Andreas Alföldi's epoch-making essay, The conversion of Constantine and pagan Rome (Oxford 1948). But whereas Alföldi sought to place the conversion within the context of late antique religiosity and the needs of government, and also to understand the forces of pagan resistance that led to the foundation of the Christian capital of Constantinople and the pagan opposition of the senatorial elite of the old city of Rome, Veyne's picture is providential, ending with the simple military defeat of paganism under Theodosius; although he claims to be a non-believer, his view of Christianity is essentially modern and Catholic: ‘The extremely complex case of Protestantism is quite another matter’ (p. 144), which he ignores. The result is a picture that resembles a Jesuit tract of the seventeenth century, quite untouched by the critical scholarship of the last three hundred years.