If an anthropologist from the star system Sirius were to teleport to earth to conduct a field study of Christianity, where would she go? A Greek monastery on Mount Athos, a papal mass in St. Peter’s, a convent hospital for the destitute in Calcutta, a snake-handling service in the Appalachians, a Quaker meeting? The figure of Jesus of Nazareth lies somewhere behind them all, but it would be hard to say exactly how, or what else they might be deemed to have in common. And if our extraterrestial anthropologist should decide to turn historian, and trace the pedigree of the Christian religion from its roots, what story would she tell? History is written backwards, hindsight is of its essence, and every attempt to characterize any great and complex historical movement is an act of retrospective construction: what is left out of the story is as significant as anything included. Is Christianity one movement or many, one story or a host of divergent narratives with few if any unifying threads?
Once upon a time historians of early Christianity could take it for granted that there were indeed true and false versions of the Christian message, right and wrong developments of its characteristic institutions. The history of the early church was the story of a single movement founded by Christ and his apostles, whose salient teachings were distilled over time into the creeds: orthodoxy, true Christianity, stood sharply defined against deviant and erroneous forms of teaching, heresy, which the church had discarded and condemned as it grew and spread.
Nowadays, we are not so sure: in a relativistic culture increasingly detached from organized Christianity, many historians are less inclined to privilege a particular story line, more prepared to view “mainstream” accounts of Christianity as the version of the foundation myth that happened to win out. In a world in which The Da Vinci Code could become a world best seller, some scholars are prepared to treat fanciful and ahistorical “gnostic” texts, written in the second century or later for esoteric groups on the margins of the Christian movement, on a par with the canonical gospels. Even sober historians nowadays are prone to speak of “Christianities” in the plural. They write of the rise of “micro-Christendoms,” the radically different and sometimes seemingly incompatible forms in which the Christian impulse, if it ever had been one impulse, metamorphosed and diversified as it adapted to changing times and cultures.
Diversity is one of the major themes of Robert Wilken’s masterly and generous-spirited account of the first thousand years of the Christian story, but he is no relativist. A former Lutheran turned Roman Catholic, he is unimpressed by the claims to mainstream status sometimes made for colorful fringe movements like Gnosticism, though he concedes their attraction in some early Christian communities. For him, under all its bewildering diversity, Christianity is clearly and recognizably one thing …