Tensions with conservatives had been building for decades, but the 60s were the real turning point. That was when middle and upper-class teenagers began rejecting the future set out by their parents to become doctors and lawyers in favour of the ideas and lifestyle of a subversive underground movement. Rejecting materialism, they set off to live in religious communes in the desert or up in the mountains, and when they returned years later, their heads were filled with big ideas about fairness, equality and a new vision for the world. Their parents thought their ideas were dumb and just wanted them to get a job.

Many did embark on careers, only ones completely at odds with the values of the older generation. Starting as lobbyists, consultants and advisers they increasingly came to hold real power and began to freeze out those who did not share their ideas. By the 90s, this youthful movement of outsiders had become grown-up insiders, holding positions in the city that commanded big salaries. Over time the cosmopolitan ruling class was completely consumed, and the movement set out to irreversibly change society — for the better, in their eyes — by enacting laws to eliminate old thinking and practices they deemed toxic and harmful. A largely urban movement, they saw the beliefs of those in the country as repulsive and backwards, a hostility that often flared into civil unrest, cultural vandalism and occasionally urban warfare. As time wore on their victory became total, and the traditions, values and beliefs of their parents were consigned to history. In a bitter twist, the world they build was not an equal one, but another type of steeply hierarchical power structure.

This was not the US Pacific Coast of the 1960s, but the Roman-occupied Mediterranean of the 360s, a time in which the cultural tide changed and the once-persecuted Christian subculture seised the reigns of the Roman Empire. What started with the faith of a single Emperor in the early fourth century came to consume the entire state bureaucracy from top to bottom by the fifth. More than this, these events altered the cosmological and social dynamics of the West and set in motion a cultural dynamo that was to characterise its evolution down to the present day. This is the story of how it happened.