Sunday, Nov. 27, is, in the Roman Catholic church’s martyrology, the feast of Josaphat: convert, anchorite, and one of history’s great artifacts of garbled translation. Josaphat, it is told, was the scion of a royal family in India. When it was foretold that Josaphat would become a Christian, his father locked him away, but a monk named Barlaam secretly met Josaphat and converted him; the king himself soon followed. Josaphat ascended the throne, but gave it up in favor of a life of contemplation. The legend of Barlaam and Josaphat became a popular medieval tale, transmitted by numerous writers, especially (and most influentially) Saint John of Damascus.

But as the literature of India and the Eastern world made its way to Europe, it became clear that the story of Josaphat was, in fact, the story of someone else: the Buddha, whose journey from aristocratic privilege to ascetic enlightenment had been, by a strange game of cultural telephone, rebooted into a fable of Christian redemption. (The name “Josaphat’’ was a linguistic mutation of the Buddhist title “Bodhisattva.’’)

That Buddhist-to-Christian sleight-of-hand was recapitulated, in a way, by none other than composer Richard Wagner. Attuned to the fashionable cutting edge, Wagner embraced the 19th-century German intellectual fad for Eastern philosophy, a vogue fueled by nationalist self-conceptions of Germany as another fount of civilization as well as Romanticist ideals of transcendence. Wagner’s favorite philosopher, Arthur Schopenhauer, incorporated Buddhist concepts into his very Germanic thought. And Wagner was familiar with the Barlaam and Josaphat story: He left behind a copy of Rudolf von Ems’s medieval German version of the legend when he fled from Dresden in the wake of the 1848 revolutions.

In exile, Wagner tinkered with the libretto for a Buddhist-themed opera, “Der Sieger’’ (“The Victors’’), about a Hindu untouchable and a monk who fall in love. The Buddha himself eventually blesses their chaste but steadfast union. Wagner never finished “Der Sieger,’’ but that theme, a love rendered more pure through renunciation, informed much of Wagner’s subsequent work, most elaborately in “Tristan und Isolde,’’ but most religiously in “Parsifal.’’ In the latter, a titular protagonist, guileless and virtuous, bears more than a little resemblance to Josaphat, and a crucial scene — in which Kundry, controlled by the magician Klingsor, tries to seduce Parsifal — is strongly reminiscent of a similar scene in von Ems’s telling of the Josaphat story. Once again, the Buddha, after a twisty chain of transformations, ended up in unwitting, unlikely disguise as a Christian hero.

Matthew Guerrieri

Matthew Guerrieri can be reached at matthewguerrieri@gmail.com.