A scholarly critique of how the term ``sodomy'' arose in the Middle Ages and came to influence Roman Catholic moral discourse. Although the story of Sodom and Gomorrah is at least as old as the book of Genesis, the view of sodomy as a form of sexual sin seems to have been invented in the 11th century by the Italian ascetic St. Peter Damian. Jordan (Medieval Institute/Notre Dame Univ.) restates the now generally accepted view that the sin leading to Sodom's destruction was transgression of the laws of hospitality rather than same-sex intercourse per se, and he gives some very relevant philosophical warnings about using centuries-old texts to find answers to modern questions. For example, there is no clear medieval equivalent for our concepts of ``homosexuality'' (a 19th-century neologism of forensic medicine) or, indeed, of ``sexuality.'' Jordan's study begins with the Canoness Hrotswitha of Saxony's account of the martyrdom of St. Pelagius, who died rather than serve a caliph's sexual desires, and Peter Damian's Book of Gomorrah. Our author guides us adeptly through the writings of Alan of Lille, St. Albert the Great, and St. Thomas Aquinas, as well as several confessors' handbooks, as he explores how the terms ``sodomite'' and ``sodomy'' were used and notes inconsistencies in emphasis and argumentation. For example, Albert the Great, contrary to his normal method, omitted medical data from his Arabic sources that would have suggested a natural (and therefore morally positive) basis for sodomy. Jordan succeeds in showing that Thomas Aquinas's analyses of luxuria and unnatural vice are inadequate for contemporary Catholicism's evaluation of gay and lesbian relationships, but the methodological problems he highlights would seem to emphasize the tradition's stance that sexual intimacy belongs to heterosexual marriage. A stimulating, if not quite convincing, contribution to Thomistic and gay studies.