They Flew: A History of the Impossible, Carlos Eire, Yale University Press, £30.

On Christmas Day 1542, in a convent near Córdoba, a woman gave birth to a baby. It was no ordinary delivery: the mother was a middle-aged nun named Magdalena de la Cruz, and her child (conceived, she claimed, through the agency of the Holy Spirit) was Jesus. After she had fed him, the infant vanished, leaving the defiant nun offering to show doubters her nipples, which she claimed were as sore as those of any new mother.

This extraordinary event was far from being Sister Magdalena’s first encounter with the divine. Her intimate relationship with God began in childhood; at five she had attempted to imitate the crucifixion by nailing herself to a wall. For more than four decades she had experienced visions and ecstasies, levitations and bilocations; she received stigmata, and claimed that the consecrated host was her only sustenance. Acclaimed as a living saint, her relics were in popular demand – including pieces of the skin which peeled off her feet when she washed them after visiting Purgatory.

From a distance of five centuries, Sister Magdalena’s story seems extraordinary. Yet, as Carlos Eire’s compelling (if slightly eccentric) new book shows, she was just one of many early modern individuals who claimed to be able to do impossible things. Among the most celebrated was the Carmelite nun Teresa of Ávila (1515-82), who began to experience visions and raptures when she was in her forties. These episodes, during which she would be lifted off her feet by an irresistibly powerful force, occurred suddenly and unpredictably; on one occasion she rose into the air while frying eggs, prompting a farcical scene in which another nun tried unsuccessfully to bring Teresa, or at least the pan, back to earth. Unusually, St Teresa wrote about her experiences, and it seems that she was a reluctant levitator: she told her brother that ‘I continually beg God not to do this’, and eventually He granted her wish.

St Teresa’s aerial activities were restrained in comparison to those of St Joseph of Cupertino (1603-63), an Italian friar whose frequent levitations were usually preceeded by a loud shriek. He flew into the air on the slightest provocation, and could stay aloft for up to two hours. Sometimes he perched on a slender tree branch, like a bird; on one occasion he lifted another priest up with him, and the two men performed a vigorous airborne dance. Other remarkable individuals were apparently able to appear in two places at once. One of the most prolific bilocators of this period was the Spanish abbess María de Ágreda (1602-65), who supposedly made more than 500 appearances in New Mexico. There she converted many of the indigenous Jumano and became known as ‘the Lady in Blue’, despite being strictly enclosed in her convent.

From the perspective of the 21st century, such stories are easy to ridicule, but Eire (a Yale professor of History and Religious Studies) makes a powerful case for taking them seriously, and considering them through the eyes of the society in which they happened. The Reformation is often thought to have ushered in a more rational worldview, and Protestants (who denied that possibility of miracles) liked to think that they had shaken off the shackles of medieval superstition. Yet this was a world in which intelligent people of both denominations believed in the Devil, and demonology was viewed as ‘a bona fide science’. Martin Luther claimed to have encountered the Devil on multiple occasions, and once threw a dog out of his bedroom window because he thought it was actually a demon. Witches were widely suspected of flying to their Sabbats, and as late as the 1680s (after Isaac Newton had developed his laws of gravity), it was possible for the Puritan intellectual Joseph Glanvill to be both a member of the Royal Society and a staunch believer in witchcraft. Consequently, although Catholics and Protestants interpreted levitations in different ways (the former hoping that they were true miracles, while the later assumed that demons were to blame), both sides acknowledged that such things could happen.

Consequently, seemingly impossible phenomena could not be taken at face value: what initially appeared to be a true miracle might turn out to be a demonic illusion, and thus all of Eire’s subjects were subject to intense scrutiny. Investigators scrubbed at the wounds of stigmatics, and Joseph of Cupertino’s body was repeatedly tested by those who suspected that his trances were mere trickery: ‘People pricked his feet with needles, seared his hands with fire, poked his eyeballs with their fingers, all in vain, because he was not really there, and his body was dead to the world.’ Other potentially miraculous events were investigated by the Inquisition, whose forensic questioning of the bilocating abbess María de Ágreda required her to explain how she had converted people ‘so barbarous that… they have no language and can only grunt’, and how she had travelled halfway around the world without getting her habit wet.

What is a modern reader to make of such stories? While many historians have either tried to explain supernatural events in rational terms, or else ignored them altogether, Eire suggests that we should stop obsessing about what really happened, and embrace uncertainty. (Much as medical historians increasingly reject crude attempts at retrospective diagnosis.) The result is an intellectually invigorating book which not only sheds new light on a formative period of European history, but also challenges the reader to think about what we accept as real, and why.

Many readers will still find it hard not to reach for rational interpretations, especially in cases where there is a plausible medical reason for an individual’s behaviour (the catatonic states which affected many of these visionaries can be caused by both physical and mental illness), or where there is strong reason to suspect trickery. Indeed, some of these miracle-workers ultimately admitted that they were frauds. Magdalena de la Cruz’s miraculous pregnancy led to an investigation into her claims, and eventually she confessed that, having sold her soul to the Devil at 12, she had spent the next 40 years having sex with demons and faking miracles. A few decades later, a Portuguese nun, María de la Visitación, admitted that her stigmata were actually self-inflicted wounds enhanced with paint, and her levitations were achieved using platform shoes and wooden poles hidden under her habit.

Yet other cases are harder to explain, even for the most cynical of readers. Joseph of Cupertino levitated to great heights and in multiple locations, both inside and outside. He performed before vast audiences (which were surely not composed entirely of credulous fools), and impressed numerous illustrious figures (Pope Urban VIII witnessed one of his flights, and promised to testify at the inevitable canonisation inquiry). His behaviour so unsettled the Catholic authorities that he spent much of his life confined to a cell, in an attempt to keep him away from the faithful. Despite multiple investigations, no-one ever managed to prove that he was a fraud. Perhaps this humble Italian friar was one of the most successful illusionists of all time? Or maybe – just maybe – he flew?