When I opened this book on a recent flight, the flight attendant exclaimed “Good book!” before taking a second look and correcting herself with a disappointed “Oh – I thought it was Fifty Shades of Grey”. She was close. Kyle Harper’s examination of the traditional narrative of the Christian prudish revolution of late antiquity is a compellingly written book about sex and shame, but the developed prose and the studiously elevated vocabulary never allow us to either wallow or delight in the sticky details.

The central focus of Harper’s book is in the transition from Roman poly-sexuality to Christian monogamy. His interest lies both in undermining various popular and academic stereotypes; that Christianity restrained and confined human sexuality with ponderous religiosity or that the Romans were consummate prudes – and in shaping a new understanding of the course of this sexual transformation.

This new history of the transformation of the “deep logic of sexual morality” is built around a series of important insights. The first is the central role of prostitution in the Roman world. The second was the important role that Christianity played in outlawing same-sex love of all kinds as well as extramarital sex of all kinds. And the third is the role that the development of the theological concept of free will played in the shaping of Christian sexual consciousness.

Harper uses these insights to make his case that Christianity transformed Roman sexuality by altering the logical underpinnings of the whole enterprise. Rather than sex being about the household or the state, it was now about the cosmos, about the individual’s relationship with God. The unhappy marriage of Genesis’ commands to “go forth and multiply” and Paul’s view that marriage was a concession to the lusty yielded complicated and diverse results but, ultimately, ended up with the radical confinement of sex to marriage.

The structuring of the book around a succession of important thinkers makes for interesting, but also beguiling, reading. Dominant voices and those authors proven by latter generations to be orthodox occupy centre stage, leaving the dissenters thoroughly radicalised. Clement of Alexandria – Harper’s darling and the “best of the apologists” – is cast as the intelligent, moderate thinker of his age. But although Clement loves to play the moderate we should not allow ourselves to be seduced by his Aristotelian rhetoric. The positioning of Clement at the heart of Church teaching obscures the importance of advocates of virginity in the early Church. There were many other fish in the sea.

Moreover, for a book that so stridently argues that marriage in the ancient world was about procreation, it is strange to find no discussion of the idealisation of adoption by both Romans and Christians, ancient Greek theories of population control, or the realities of contraception and infant exposure. As excavations of the sewer systems under Roman brothels have horrifyingly revealed, not everyone saw children as a blessing. And while Christian theologians may have dismissed same-sex love out of hand, it is difficult to deny the homoerotic undertones of the love between saints Sergius and Bacchus or Paulinus of Nola’s chaste love for Christ. The legislation may have been radical and clear-cut but the evidence can be queried.

All of this aside, the book is, as Harper admits, a synthesis, and as such it follows the arc of history’s tediously moralising rising star: orthodox Christianity. The flight attendant’s instincts were excellent: this is a good book. But she’d be appalled by the prudish central character and horrified that the only tough love is found in the strident demands of the academic writing style.

Candida R. Moss is professor of New Testament and early Christianity, University of Notre Dame.