The belief that ours is the most gloriously modern of ages, rooted in reason and revelling in novelty, is so widely held that Ferdinand Mount’s elegant riposte comes as something of a shock. It is disconcerting to think that we’ve been here before, that the ancients were absorbed by exactly the same sorts of fads and foibles that enliven and trouble our lives today, that in so many ways we are them and they us.

Think of the cult of the celebrity. You can trace a line directly from the mawkish excesses of the public’s reaction to Jade Goody’s illness and death last year, to the extraordinary aftermath of the death in AD 130 of Hadrian’s lover Antinous. So distraught was the Roman emperor that he founded a city bearing the handsome lad’s name, a vast project three miles in circumference, every column along the mile-long main street bearing his statue. Napoleon’s surveyor Jomard counted 1,344 busts or statues of Antinous in two streets alone. Seventy cities across the empire rushed to erect temples in his honour. His profile even popped up on Roman coins. Antinous was duly deified, the last non-imperial mortal to be made a god. Celebrity culture gone mad, as the tabloids might put it.

Talking of religion, today’s spiritually consumerist pick-and-mix smorgasbord recalls the panoply of choices for the inquisitive Roman. On the one hand there was official religion, on the other were the clutches of cults and the widespread worship of Mithras, Isis, Serapis and a host of others. For anyone who thinks astrologers belong firmly in the ancient world, when they enjoyed enormous authority under the Romans, remember Ronald Reagan consulting his pet astrologer Jean Quigley on weighty matters of state, such as exactly when to sign the Intermediate Nuclear Forces Treaty in 1987. Then there is Cherie Blair and her feng-shui expert, her magic pendant that served as a Bioelectric Shield and her attachment to the New Age guru Carole Caplin. Across the Atlantic, Sarah Palin, George Bush and Barack Obama all profess born-again experiences.

Mount mounts a compelling and amusing case for parallels between the sexual free-for-all of ancient Greece and Rome and the no-strings-attached world of today’s “zipless fuck”, a phrase he enjoys so much he can’t help spraying it across a memorable chapter on The Bedroom. He reminds us of the Neo-Pagan yearning for a return to the sexual laissez-faire of the ancient world, quoting Lytton Strachey’s exuberant response to reading Plato’s Symposium in 1896, wishing he had sat at the feet of Socrates and seen the Athenian statesman and general Alcibiades. In EM Forster’s Maurice, when undergraduates reach the part of Plato’s Phaedrus in which he describes same-sex passion with poetic force, the teacher remarks with wearily Christian fervour: “Omit: a reference to the unspeakable vice of the Greeks.” The ancients may not have been forever capering around with erect penises to the fore, yet their sexual behaviour and thinking were a world away from the joyless Christian dogma of sex and original sin.

Ancient baths and today’s spa “experiences” and “pampering”; Socratic dialogue and trial by Paxman; the Greek gymnasium and our cult of fitness; pretentious galloping gourmets such as Archestratus, devotee of grey mullet and sea bass, and the obsessive creations of Heston Blumenthal. However dispiriting it may be to acknowledge, it’s hard to duck the conclusion of this splendid book that we’ve been here before, that the Christian-dominated space between the ancients and our era was a strange, normal-rules-do-not-apply interregnum.

It reminds me of the wise observation by Joseph Brodsky in Of Grief and Reason, not mentioned here, that “one of the saddest things that ever transpired in the course of our civilisation was the confrontation between Greco-Roman polytheism and Christian monotheism, and its known outcome”, an altercation that was neither intellectually nor spiritually necessary.