St Augustine wasn't always so saintly, which is why his honest 'Confessions' still resonates today

When St Augustine appeared to Bob Dylan in a dream, he spoke in two very different voices. First, he was the preacher with “fiery breath” who scorches his listeners “without restraint”.

Then he became an ordinary man whose “sad complaint” moves Dylan, as he sings in the final plangent line of his 1967 song I Dreamed I Saw St Augustine, to bow his head and pray.

It is precisely this combination of spiritual fervour and acute self-analysis that makes Augustine’s Confessions, in which the North African bishop recounts his past sins and conversion to Christianity, so unusual and compelling, even 16 centuries later.

There have been hundreds of books on Augustine. The Oxford classicist Robin Lane Fox adds to their number with this long and detailed – perhaps overlong and overdetailed – work tracing the future saint’s life from his birth in 354 to the composition of Confessions in his early 40s.

Lane Fox sets Augustine’s life in its historical context by including the life stories of two of his near-contemporaries: Synesius, a philosophy-loving bishop; and Libanius, a pagan with a penchant for autobiography.

For long stretches of the book, however, these two figures fade from view. You can hardly blame Lane Fox for being drawn back to Augustine.

Birth of St Augustine, by Antonio Vivarini, circa 1440

We know more about him than any other figure from the ancient world, and his personality and intelligence shine more brightly than his contemporaries.

Confessions is not strictly speaking an autobiography; it is a prayer addressed to God. But, as Augustine says, God knows it all already and so he can speak freely about his own sins – most notoriously, his sex life.

Augustine tells us he prayed for chastity, but “not yet”

When he was 15, his father, Patricius, spotted him naked at the baths and was delighted with his budding virility. For Augustine, this was not a good omen.

Patricius was a pagan who compulsively cheated on his long-suffering Christian wife, Monica. Augustine inherited his father’s sexual appetite. Moving to Carthage as a young man, he embroiled himself in a “seething cauldron of lust”.

He admits even to “procuring the fruits of death” while in church – Lane Fox tells us it was common for randy churchgoers to pick up married women in the aisles. He also took a long-term concubine with whom he had a son.

Augustine tells us he prayed for chastity, but “not yet”. (Noël Coward alludes to this famous phrase in Brief Encounter, where the lovers prolong their doomed affair with cries of “not yet”.)

When he sent his concubine away, it was, he says, like someone “being torn from my side”, like Eve was from Adam’s rib. (It would be fascinating to compare the concubine’s side of the story – but as with many ancient women of low rank, she goes unheard.)

To Augustine, premarital sex was a false vision: “I was not yet in love but I was 'in love with love’.” As he came to reject sex, so he rejected Manichaeism. Their religion’s founder, the prophet Mani, claimed the world was divided into equally powerful forces for evil and for good, darkness and light.

Augustine knew, though, that he did not have a divided soul; instead it sometimes inclined to right and sometimes to wrong. Evil was part of human nature – which is why he came to popularise the doctrine of “original sin”.

Augustine learnt this from reading the Bible, but also from personal experience. As a teenager, he and a gang of friends stole pears from an orchard (echoes of Genesis again). Augustine had been led astray by something that initially seemed worthwhile: friendship.

Later, in Carthage, he joined a student club called “the Overturners” – the Bullingdon Club of its era – whose members went around harassing other students. He joined because he was lonely. He slept around for the same reason.

He came to realise that far from being cleanly divided into light and dark, our vices are often misdirected virtues. The combination of brilliant dramatic set pieces and close emotional self-scrutiny makes Augustine’s Confessions read like the work of a great novelist or poet.

An early 14th century painting of Augustus Credit: Ann Ronan Pictures/Print Collector/Getty Images

As Lane Fox astutely points out, his journey echoes that of Virgil’s Aeneas, with the role of the abandoned Dido taken by his mother. His reflections on time anticipate Proust’s (“I can be glad to remember sorrow that is over and done with and sorry to remember happiness that had come to an end”).

Tolstoy based his memoir of religious conversion, A Confession, on Augustine’s. Gerard Manley Hopkins, priest and poet, captured his artfulness by describing Augustine’s slow turn towards God as a “lingering-out sweet skill”.

Lane Fox is informative and learned, but his book is, I must confess, a bit of a slog. Still, some intriguing suggestions are scattered throughout. Examining a letter from the time Augustine wrote Confessions, he discovers the bishop was suffering from exochadae (piles) and rhagadea (anal fissures).

Might this great work of Christian literature have been written to distract its author from excruciating pain? It feels like an appropriately intimate speculation for so intimate a book as Confessions, in which we see a man laying his body and soul naked before God – and his readers.

Order Augustine: Conversions and Confessions from the Telegraph bookshop for £20

656pp, Allen Lane, £30, ebook £12.99