Pope John VIII, a scholarly priest who had studied in Athens, was elevated to the papacy in 855. After almost two and a half years, it was discovered that John was actually a woman in disguise. “Pope Joan” was removed from office in disgrace and any mention of her reign expunged from official church records. Nonsense, reply Catholic historians. The story of Pope Joan was a medieval myth—a legend kept alive for centuries by enemies of the church despite a lack of hard evidence.

Peter Stanford, a British author and former editor of The Catholic Herald, ends his wide-eyed account of his search for the truth about Pope Joan by accepting both positions: He believes in the existence of Pope Joan, but admits he can’t prove it. Along the way, readers will be fascinated by his pursuit of this most famous figure of religious folklore.

The Legend of Pope Joan by Peter Stanford (Henry Holt, $25)

References to a female impostor on the papal throne first appear in religious writings about 1150, although the details vary sharply from account to account. Most of the “facts” of the Pope Joan legend were related by Martin Polonus in his Chronicon Pontificum et Imperatum, a 1265 papal history. His one-paragraph account places Joan’s reign from 855 to 858, between popes Leo IV and Benedict III and lasting “two years, five months, and four days.” Polonus identifies Joan as being of English descent, a former resident of the German city of Mainz, and a student in Athens who later won fame in Rome as a noted scholar. He also affirms the key tale of the Joan legend—that the woman pope was impregnated by a lover and exposed as a fraud after she went into labor on a Roman street during a papal procession.

While the Polonus account appears some three centuries after the original events, his acceptance of Pope Joan is undeniably significant. The Polish Dominican priest was papal chaplain under Pope Clement VI and, given his access to church records in writing his chronicles, his confirmation of the Pope Joan legend was considered tantamount to an admission by the church itself. At least there’s no evidence that Polonus was ever contradicted or punished in any way for his writings; he continued to update his papal history over the next dozen years, and was later appointed archbishop of the Polish city of Gneisen.

Over the next two centuries, until Protestant reformers seized on the Pope Joan tale as evidence of the corruption of the papal system, the existence of the female pontiff was accepted by many European Catholics. A statue of Pope Joan stood on the streets of Rome until around 1550; her bust was included with those of other popes in the Cathedral of Siena until about 1600. Since that time, church authorities and Catholic writers have dismissed the Pope Joan story as a folktale.

Stanford organizes his book along the lines of his search as he follows each thread of the Pope Joan legend. Given the passage of time, there is a serious lack of documentary evidence about the events of Joan’s era. The oldest documents in the Vatican archive date back only to the 11th century; original editions of many of the books Stanford used have long since disappeared, so he had to rely on copies produced many years later. Also, given the prominence of the Pope Joan legend during the Reformation, any evidence of her existence would surely have been destroyed by church officials at that time.

Since Stanford can only examine the likelihood of each of Polonus’ claims, his case is doomed to be largely circumstantial. History has provided many cases of women masquerading as men (and vice versa) and the customs of the time would have aided the young Joan. Priests of the mid-ninth century wore long robes, often with hoods, and were clean-shaven. In the Dark Ages, people seldom bathed and usually slept in their clothes. Further, scholars from Athens were popular figures in the Rome of Joan’s era, and the tradition of choosing only Italian churchmen as pope had not yet been established.

In fact, there wasn’t a great deal of quality control in the selection of popes, resulting in quite a rogues’ gallery of pontiffs. Pope Leo III (795-816) was a corrupt adulterer. Pope Sergius II (844-47) delegated most of his papal responsibilities to his brother, who promptly appointed himself a bishop and began selling indulgences. Grudge-carrying Pope Stephen VI (896-97) had the body of a previous pope exhumed to stand trial for violating a church rule (the corpse was convicted, perhaps owing to a less than energetic defense). Various Roman families also interfered in the papal selection process. It was considered quite a status symbol at the time to have your son appointed pope—Pope John XII (955-64) was just 18 years old when he took office.

Given the limits of history, The Legend of Pope Joan is unlikely to change anyone’s firmly held convictions, but it’s a riveting read.