Ramsay MacMullen has an encyclopedic knowledge of the Roman empire and early medieval world. But what sets him apart is his ability to mine obscure texts for asides or offhand comments, and then use those fragments to illustrate fundamental point about the society.
A case in point. In Christianity & Paganism in the Fourth to Eighth Centuries Prof. MacMullen uses a minor work of Gregory of Tours (c. 538-594) to demonstrate the stubborn persistence of paganism among the country folk in southern Gaul well into the Sixth Century. In a work called Vitae Patrum (Lives of the Fathers), a frustrated Gregory recounted a voyage in which he was the only Christian amidst a sea of pagans. Prof. MacMullen sets the stage:
The depth of Christian belief had perhaps always been limited and the evidence of conversion . . . easy to exaggerate. Even from the longest-evangelized, most completely church-ed area down to Provence, in the 580s, when a man took passage on a vessel bound for Italy, he might find "a great crowd of pagans getting aboard along with me, among all of whom, that crowd of country people, I was the only Christian."
Many would have skimmed over Gregory's observation without a second thought. Prof. MacMullen spells out the implications:
The incident is very revealing, not least in the matter-of-fact tone of the narrative. It fits easily with all the other evidence accumulated in the notes above, showing in still more advanced periods the persistence of this or that pagan custom, the survival of one or another ancient rite.