For a biographer, there is no greater insult than to be called a hagiographer - especially if the subject is a saint. Hatchet jobs sell better than hagiographies; holy men and women seem to interest us only if they can be unmasked as frauds.
The purpose of this new biography of St. Augustine is artfully implied in its title: this is not a book about a "saint and sinner", but the sinner first and foremost, his posthumously awarded sanctity only an afterthought. Indeed, James O'Donnell, an American classicist and expert on late antiquity, even asks whether Augustine (whose "webmaster" he is) can be "rescued from his sainthood before he dies completely a second time."
But would Augustine want to be "rescued" in this way? He was a saint not because he did not sin but because he repented. After all, he wrote the original warts-and-all portrait of himself: the Confessions.
Without that first and greatest of all autobiographeis we might not know or care very much about a fourth-century bishop of Hippo, even one who ended up as one of the most enduringly influential of all Catholics.
It is true that, in sofar as readers know much about Augustine, it is thanks to the Confessions. His phrase "give me chastity, but not yet" has entered the vocabulary of comedians who have never heard of the saint. O'Donnell insists that "Augustine's early medieval audience seems to have paid this book relatively little attention", but he later mentions that Pelagius, the British monk with whom Augustine later engaged in a celebrated controversy about free will and predestination, actually attended a publi reading from the Confessions in Italy. This suggests that the book was already widely disseminated in Augustine's own lifetime, and it has never really gone away.
O'Donnell's irreverent approach will irritate many readers, as he knows full well. He even parodies their response: "This is Saint Augustine, for crying out loud, and he's talking to God, right?"
But O'Donnell really knows the subject inside and out. In this book, often exhilarating and occasionally exasperating, he succeeds in his purpose of forcing us to look afresh at a monumental classic and its equally monumental author.
What O'Donnell does is to question all our assumptions about the world in which Augustine lived, a world which still shapes so many of our ideas today: the nature of asceticism, the role of religion, the notion of a "catholic" (universal) church, the contrast between Christian and pagan. It was Augustine, he argues, who created all these assumptions, if not ex nihilo, then at any rate from something quite different.
Indeed, O'Donnell credits Augustine with authorship of the intellectual landscape in which we have lived ever since. So successful was he in steamrollering all his rivals that their alternative scenarios have been blotted out by his towering polemical presence.
It was, he argues, Augustine who "invented" Christianity, in the sense of a single creed based on canonical texts, practised in centrally defined forms, and claiming exclusive, "supervening" truth with a seriousness that pervades the whole of human existence. It was Augustine who bequeathed his inner conflits about sex and guilt and original sin for posterity to torment itself with; Augustine who taught us to revere books as guides for the perplexed; and it is Augustine's God who has presided over history.
These are bold claims, asserted rather than demonstrated. To imagine virtual histories in which Augustine did not exist, or in which his views did not evolve as they did, is a fascinating experiment, but it does not prove anything. Yet if O'Donnell is occasionally guilty of overstating Augustine's importance, he at least avoids the opposite temptation of belittling him. By depicting the saint from the point of view of his opponents - Manichees, Donatists, Pelagians - the author is able to show how Augustine's tough-minded positions supplanted what had hitherto been considered mainstream. Occasionally, he reminds one of a typical American liberal academic curling his lip at the excesses of the Christian right.
Augustine may have invented the idea of objective truth, which secular thinkers of all kinds have appropriated, but this was a by-product of the only kind of truth that he believed mattered: the truth that God, through Jesus Christ, is embodied in humanity and preserved in the Catholic Church.
Augustine would have been baffled and indignant to be told that this Church was his invention, but he would have understood and approved of Pope Benedict XVI's battle against secularism. The Pope is never more embattled than when at his most Augustinian, echoing Augustine's harsh dictum: Salus extra ecclesiam non est (There is no salvation outside the church).
And this is the book's major flaw. It does not seriously consider the Christian, and specifically the Catholic, answer to O'Donnell's question: "Who was Augustine?" Yet that is the one interpretation that makes sense of what the man thought he was doing. Whoever else he was, he was a Doctor of the Church able to teach authoritatively what was Catholic, precisely because he had first-hand knowledge of what was not Catholic.
The architect of the City of God needed to build high walls around the faith because he lived in a time when civilisation itself seemed on the edge of collapse. Without figures like Augustine who give civilisation its purpose and meaning, who can say whether its survival is certain even today?
Daniel Johnson is a columnist for the "New York Sun"