A medieval philologist, Boswell spoke or read several Scandinavian languages, Old Icelandic, German, French, Spanish, Italian, Latin, Greek, early and modern Russian, Old Church Slavonic, Armenian, Persian, Arabic, Hebrew, Syriac, and Akkadian.

[1][2] Boswell received his doctorate in 1975 and joined the Yale University history faculty, where his colleagues included John Morton Blum, David Brion Davis, Jaroslav Pelikan, Peter Gay, Hanna Holborn Gray, Michael Howard, Donald Kagan, Howard R. Lamar, Jonathan Spence, Robin Winks, William Cronon, and Edmund Morgan.

Boswell made many detailed translations of these rites in Same-Sex Unions, and stated that one mass gay wedding occurred only a couple of centuries ago in the Archbasilica of Saint John Lateran, the cathedral seat of the Pope as Bishop of Rome.

This aspect of Boswell's text has drawn significant scholarly debate, with critics contending that these rites represented adoption or fraternity rather than sexual unions.

[6][7][8] Boswell pointed out such evidence as an icon of two saints, Sergius and Bacchus (at St. Catherine's on Mount Sinai), and drawings, such as one he interprets as depicting the wedding feast of Emperor Basil I to his "partner", John.

[10][11][12][13][14][15][16] James Brundage, professor of history and law at the University of Kansas, observed that "the mainstream reaction was that he raised some interesting questions, but hadn't proved his case.

[17] Welsh LGBT historian Norena Shopland, in Forbidden Lives, examines a number of translations of Gerald of Wales's extract from the third book of Topographia Hiberniae, "A proof of the iniquity (of the Irish) and a novel form of marriage".