LAST year, as Europe marked the 500th anniversary of the Reformation, thousands of words were penned by people trying to figure out that grim era when the continent found itself plunged into bloody conflict between the Catholic and Protestant versions of Christianity.

Peter Leeson and Jacob Russ, two American economists, have come up with an unlikely take by focusing on one particular aspect of the conflict: witch trials. The so-called “great age” of witch trials began around 1550, as the Reformation was gathering pace, and did not end until around 1700. By that time 80,000 people had been tried for sorcery, and half of them executed. The great majority of the victims were female.

Messrs Leeson and Russ believe that an upsurge in trials reflected “non-price competition” between the Catholic and Protestant churches. That competition was for the hearts and minds of a population that was pious, superstitious and easily persuaded of the need to stamp out evil.

In the preceding centuries, ordinary folk had believed no less strongly in the existence of dark forces, and of individuals who had the power to conjure them up, but the church discouraged people from holding this belief or acting on it. (In 1258, for example, Pope Alexander IV issued a canon aimed at preventing witchcraft trials.)

Another feature of that pre-Reformation period, the authors note, was that the Catholic church generally felt powerful enough to deal with pockets of opposition by isolating and neutralising its ideological opponents. Dissident sects like the Cathars were denounced as heretics and eventually crushed.

All that changed when the the Reformation gained ground in Europe’s Teutonic heartland, a patchwork of small states. Some local rulers embraced the new Protestant faith; others did not. In this very fluid situation, local Catholic authorities felt a need to impress the faithful with their effectiveness in stamping out evil; Protestant authorities made similar displays of their own zeal and prowess. This is how the authors sum up their theory in a paper for the Economic Journal:

Europe’s witch trials reflected non-price competition between the Catholic and Protestant churches for religious market share in confessionally contested parts of Christendom. By leveraging popular belief in witchcraft, witch-prosecutors advertised their confessional brands’ commitment and power to protect citizens from worldly manifestations of...evil.

This is not a completely original hypothesis but the authors lend weight to it by applying some of their own wizardry as number-crunching economists. (Mr Leeson is a professor of economics and law at America’s George Mason University; Mr Russ was his student.) They collected data on more than 43,000 people prosecuted for witchcraft between 1350 and 1850 across 21 countries. They also looked at 400 instances of Protestant-Catholic rivalry. They find that surges in witch trials correlate closely, in both time and location, with intense sectarian competition.

Putting people on trial and executing them publicly is a burdensome but worthwhile way for a ruthless authority to flex its muscles and impress ordinary folk, the authors note. They compare this with Stalin’s trials of his political enemies. The outcome was never in doubt—and Stalin could just as easily have had them quietly assassinated—but public trials served the purposes of “education” and propaganda.

Only briefly do the authors touch on another notorious episode of witchcraft mania: the trials in Salem, Massachusetts in the late 17th century. There, too, they suggest that competition was at work. In this case it was not between sects or doctrines, but between individual Puritan (i.e. hard-line Protestant) ministers for congregations.

Any modern practitioner of the Protestant or Catholic faiths will shudder at the horrific purposes to which their beliefs were once put. Of course, they will say, it was all a very long time ago, and (as the emollient, inter-faith commemorations of last year brought home) doctrinal differences within Western Christianity are no longer seen as a reason to burn one another. (Even in Belfast, it is only effigies of the pope, and other Catholic paraphernalia, which are committed to the flames during zealous Protestant celebrations.) These days, German Protestants and Catholics are more likely to meet one another as fellow workers for the same charities than as contestants in an ideological battle.

What has changed? As a general rule of thumb, it might be said that religion either makes people look inward, in search of a better understanding of their own weaknesses, or it makes them look outward, in a quest (which can easily become fanatical) for external sources of evil. One impulse can tip over into the other very easily, and that danger never goes away.