For legions of Catholics, and not a few church bureaucrats, the supernatural is as real and present as it was for their medieval forebears.

In “The Vatican Prophecies: Investigating Supernatural Signs, Apparitions and Miracles in the Modern Age,” veteran Catholic journalist John Thavis explores their world of Marian apparitions, relics, exorcisms, doomsday visions and other purported encounters with the supernatural.

Thavis, who for nearly three decades was Vatican bureau chief for Catholic News Service, unfolds the elaborate processes the church employs for scrutinizing the allegedly miraculous. The church accepts enough science to avoid unchecked superstition, but it also affirms the supernatural when it concludes there’s no other explanation.

“In an age in which Christianity is supposed to be the faith of reason, many are still fascinated by the possibility of miracles, apparitions, encounters with the devil and other signs of the supernatural,” Thavis writes.

Balancing faith and reason “has increasingly occupied the Vatican’s time and resources,” he writes. “In a sense the Vatican is engaged in vetting the supernatural and filtering ‘wondrous’ experiences, to minimize anything it judges unorthodox, superfluous, excessive or bizarre. At the same time, of course, Rome cannot be seen as placing limits on divine intervention.”

Vatican book

Vatican book

Echoing that approach, Thavis takes such investigations seriously but is jaded enough to spice his work with gently irreverent prose. He describes one Marian phenomenon as the “Area 51” of conspiracy theorists and another as a “Marian road show” involving dubious claims. One of the Vatican’s worries is that “Mary,” or her purported mouthpieces, might spout heresy.

Claims of appearances of the Virgin Mary and other miracles have come in so fast and furiously that the Vatican itself can’t screen them all and is increasingly trying to get local bishops to make their best judgments. But in a mass-communication era, a shrine or event can become an international sensation long before the vetters get their boots on.

Nowhere is that more evident than in Medjugorje, Bosnia-Herzegovina, where reports of regular appearances of the Virgin Mary since 1981 have transformed a dusty Croat village into an international destination for multitudes of pilgrims.

The Vatican is still investigating Medjugorje’s validity, but “Catholic devotees had already voted with their feet,” Thavis writes. He quotes one Vatican official troubled by the visionaries’ ties to rebel friars: “We can’t expect Mary to have a degree in canon law, but she should at least be aware of the general rules of the church.”

The book also includes remarkable passages on the veneration of Catholic relics.

Even more stunning, and disturbing, is Thavis’ account of exorcisms and other encounters with the dark side. In one recent case that involved child protective services in Indiana, as well as a Catholic exorcist, even medical and law-enforcement workers were mixed on whether demons or delusions were involved.

What does Pope Francis make of all this? He seems to reflect the church’s mixed approach. The onetime chemist embraces science and modernity in many ways, but he also believes strongly in the activity of good and evil spirits among us, and he has a great devotion to Mary and the saints. Yet Francis cautions that Mary “is not a postmaster, sending messages every day.”

This is the second book in quick succession for Thavis. His first, “The Vatican Diaries” (2013), was an eye-popping memoir of the sometimes corrupt, sometimes petty and occasionally sublime world of the Roman Catholic bureaucracy.

For this book, Thavis traveled across America and Europe to the datelines of the supernatural. We can be grateful that his supposed retirement years have been anything but.

“The Vatican Prophecies: Investigating Supernatural Signs, Apparitions and Miracles in the Modern Age.” By John Thavis. Viking. 276 pages. $27.95.

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