Father René Laurentin around 1960. He studied apparitions of the Virgin Mary reported around the world. (University of Dayton Marian Library/University of Dayton Marian Library)

In the past few centuries, the Catholic Church has authenticated just over a dozen apparitions, visions of the Virgin Mary that have appeared to French nuns and schoolchildren, Portuguese shepherds and Rwandan youth, and inspired millions of pilgrims to visit shrines and churches scattered in small towns across the world.

Mary appeared 18 times at Lourdes, in southern France, in 1858. She revealed herself to a group of children six times in Fatima, near Portugal's western coast, in 1917.

In all, according to the Catholic priest René Laurentin, Mary has reportedly appeared more than 2,400 times since the Middle Ages, in visions described by children in the former Yugoslavia and by a man in Marlboro, N.J., who said he saw the mother of Jesus while seated on a plastic bucket in his back yard.

Father Laurentin, a French theologian who died Sept. 10 at 99, was perhaps Catholicism's preeminent scholar of contemporary miracles and Marian apparitions. A student of the French philosophers Jacques Maritain and Henri Bergson, he combined a sense of academic rigor with a religious faith shaped by World War II, when he was captured by Nazi forces in Belgium and imprisoned for five years.

"He possessed the solidity of the theologian, the seriousness of the historian [and] the agility of the journalist," wrote Lourdes rector André Cabes in a statement on his death.

Father Laurentin specialized in Mariology, the study of the Virgin Mary, but his columns for France's Le Figaro newspaper and his scores of books often ranged far afield. He investigated the story of Richard Thomas, a priest in Texas who supposedly multiplied tins of condensed milk to feed the masses. And he studied the claims of Greek Orthodox evangelist Vassula Ryden, whom Father Laurentin called "the most authentic mystic living in the world today."

But he was best known for his studies of Lourdes, which he began in the early 1950s after the town's presiding bishop, Pierre-Marie Théas, urged him to take on the project with the admonition "Lourdes needs only the truth."

Father Laurentin spent more than a decade combing the archives for documents surrounding 14-year-old Bernadette Soubirous, who said she had been instructed by Mary to build a chapel at a cave near the town, and presenting the story of the apparitions in a way that balanced scholarship with literary style.

The effort proved remarkably successful, at least in the eyes of the bishop. "Nothing so beautiful or luminous has ever been written," Théas wrote after reading Father Laurentin's first volume, "The Meaning of Lourdes" (1955). "Really, after reading you, we know better the solidity and the seriousness of the pilgrimage. You reveal the mystery of Lourdes and its place in the life of the Church."

Father Laurentin went on to publish a seven-volume compendium of documents about the Lourdes sightings, as well as a six-volume "Authentic History of the Apparitions."

About that time, he also served as a consultant to the preparatory commission for the Second Vatican Council, which began in 1962, and participated as a scholar, taking notes on the proceedings at a time when the church was facing questions over Mary's role in the faith.

Outside of the Trinity — God, Jesus and the Holy Spirit — Mary has become one of Catholicism's most important Biblical figures. Though fully human, she is believed to be without sin. She became a particularly popular figure during the papacy of John Paul II, whose Latin motto — totus tuus, totally yours — referred to Mary, and who was nearly killed in 1981 during an assassination attempt that he said was thwarted by a Marian intervention.

Yet Father Laurentin, whose expertise was increasingly put to use as reports of apparitions increased in the 1980s and '90s, resisted placing an outsize emphasis on Mary. "Mary is the model of our faith, but she is not divine," he told the New York Times in 2000. "There is no mediation or co-redemption except in Christ. He alone is God."

René Laurentin was born in Tours, France, on Oct. 19, 1917, to an architect father.

Father Laurentin — he was ordained in 1946 — studied Thomist philosophy at the Catholic University of Paris and philosophy at the Sorbonne. He received a doctorate from each school after his army service, for which he received the War Cross, and later served as a professor of theology at the Catholic University of Paris and the Catholic University of the West in Angers, France.

The Sanctuary of Our Lady of Lourdes announced his death but did not provide additional details.

Father Laurentin was often asked whether he believed in particular apparitions, a contentious question for a priest, let alone a bishop — the first person charged with adjudicating claims of supernatural occurrences.

The church, Father Laurentin wrote in one essay, used four criteria to grant recognition to a supernatural occurrence: whether the message of the apparition is in accordance with Christian teachings; the seer is "sincere, credible, coherent and disinterested"; acts of healing or physical signs of a supernatural presence occur; and long-term religious conversions follow from the incident.

Even when an occurrence has been recognized, Father Laurentin noted, individual Catholics were not obligated to believe. Belief as a whole, he said, was entirely out of his purview — though he seemed more sympathetic than many Catholic priests and scholars in his opinion of Medjugorje, a town in the former Yugoslavia where Mary has allegedly appeared regularly since June 1981.

"If someone asks me if I believe in Medjugorje, I say, 'I am not obliged to answer to this question.' I am an expert; I examine reasons in favor and reasons against," he told a priest in 2003. "Let each one judge for himself and let [the] Church judge for all of us."