Cults, generally speaking, are a lot like pornography: you know them when you see them. It would be hard to avoid the label on encountering (as I did, carrying out field work last year) 20 people toiling unpaid on a Christian farming compound in rural Wisconsin – people who venerated their leader as the closest thing to God’s representative on Earth. Of course, they argued vehemently that they were not a cult. Ditto for the 2,000-member church I visited outside Nashville, whose parishioners had been convinced by an ostensibly Christian diet programme to sell their houses and move to the ‘one square mile’ of the New Jerusalem promised by their charismatic church leader. Here they could eat – and live – in accordance with God and their leader’s commands. It’s easy enough, as an outsider, to say, instinctively: yes, this is a cult.

Less easy, though, is identifying why. Knee-jerk reactions make for poor sociology, and delineating what, exactly, makes a cult (as opposed to a ‘proper’ religious movement) often comes down to judgment calls based on perceived legitimacy. Prod that perception of legitimacy, however, and you find value judgments based on age, tradition or ‘respectability’ (that nice middle-class couple down […]