Anyone who thinks that witchcraft belongs only to our past and imaginations should think again. Tens of thousands of people were executed as diabolists between the 15th and 18th centuries, an episode that for many signifies an age of ignorance and intolerance from which the Enlightenment saved us. There's some truth in this. And yet much of the world still believes in witches, their supernatural powers and malevolent intentions. And all too often the accused are abused and ostracised, or tortured and killed.
Here is one story. It happened in India's Jharkhand state in October 2009, but might have come from any part of early modern Europe. Five women were accused of causing harm, a suspicion bolstered by local witchfinders and a cleric. A mob dragged them before a large crowd, where they were stripped and beaten until the authorities intervened. They were lucky. Every year hundreds of Indians, mostly women, are murdered by their neighbours, usually in the most atrocious manner.
In sub-Saharan Africa the problem is even worse. The war in Congo (1998-2003) killed millions, mostly through starvation and disease. High child mortality was widely blamed on "night dancers" – witches who steal blood and smear poisons on houses. European witches of the 16th century were charged with identical crimes, for instance the Swiss plague-spreaders known as engraisseurs. In 1999 the pro-government chief of Mwenga fled an advancing rebel army, leaving his wife behind with the town's protective charm; the soldiers publicly buried her alive with the charm. In the province of Ituri, as many as 4,000 may have been killed.
The history of witchcraft helps us to understand this tragic phenomenon. Unfortunately, the subject remains littered with powerful myths. Some modern witches sing a protest song called Catch the Fire, which mentions the 9 million women burned during the "witch-craze". Dan Brown's Da Vinci Code says 5 million. The actual figure was about 50,000. This still might seem a lot for an imaginary crime, but viewed in context of time, space and population levels, it's clear that witch trials were comparatively rare. Plus executions followed in only about half of trials.
This demonstrates that our ancestors were much more cautious about prosecuting witches, and courts more unwilling to convict, than we might imagine. The idea that powerful states and fanatical clergymen launched mass persecutions to suppress the peasantry (especially women) is generally false. The impetus for most accusations came from below, and the role of the state was to dampen witch-hunting ardour in the interests of justice and order. One of the most compelling pieces of evidence that witch-hunting was a campaign waged by the medieval Catholic church turned out to be a 19th-century forgery, just as the figure of 9 million was an 18th-century miscalculation.
England only experienced one serious witch-panic, in the eastern counties during the 1640s. It was intense but brief, its causes and termination suggesting why persecution for witchcraft came to an end and why it endures around the world. This was a time of economic depression, poverty and social dislocation, political and legal disruption, and civil war. Almost all the offices and institutions, not least a sceptical monarch, that had restrained mass witch-hunting had collapsed. A sense of anxiety and suspicion, and a willingness to resist evil with violence, were pervasive. The similarities with the Congolese crisis are striking. When order was restored in England, witch trials did not cease, but rampant witch-hunting did.
In September 2009 the UN identified witch-hunting as "a form of persecution and violence that is spreading around the globe". In July this year the Witchcraft and Human Rights Information Network, an organisation established last year, will hold its first conference devoted to alleviating the crisis in developing countries.
The ferocity of witch-beliefs, however, knows no frontiers. The fundamentalist churches of some African communities in the UK sustain the concept of demonic possession and the need to fight it by physical means. In 2005 three Londoners were convicted of cruelty to an eight-year-old Angolan girl they believed to be a witch. Her tormentors, one of them her aunt, had tried to "beat the devil out of her". The trade in body parts taken from albinos in Tanzania for use in muti magic, also crosses borders and continents.
Far from being a historical curiosity, then, witchcraft is a living problem, a belief in occult forces to which all human beings are prone, but manifested in a way that is horrifically unfamiliar to people in the west. It can even spread to affluent societies, but obviously cannot trigger mass persecutions there. In Africa, India and south-east Asia, better education is important in the war against witch-hunting, but without the conditions that prevent neighbour fighting neighbour for scarce resources, and lawless armies unleashing rough justice, the spread of enlightened ideas will not be enough to stop the killing.
• This article was commissioned following a suggestion made by one of our readers, Christina Meredith. If you would like to propose your own subjects for us to cover, please visit the latest You tell us thread