Cahill's latest engaging romp through pop intellectual history (after Sailing the Wine-Dark Sea) focuses, despite the subtitle, not on fringe cults, but on the mainstream of medieval Roman Catholic thought. Instead of obscurantist dogma, he finds a ferment of implicitly progressive ideas that laid the groundwork for modernity. The veneration of the Virgin Mary, he contends, prompted a boost in women's status, exemplified by the mystic nun Hildegard of Bingen, who gained public status and power as a spiritual figure. The papacy's claim of spiritual authority independent from temporal power contained the seeds of modern notions about the separation of church and state, democracy and the legitimacy of political dissent. And the perennial head scratching over the doctrine of transubstantiation, he argues, stimulated the beginnings of both empirical science and artistic realism. Cahill's treatment is more impressionistic than systematic, and built around lively profiles of iconic medievals like Abelard and Héloïse, Francis of Assisi and Giotto, whose paintings get a long, lavishly illustrated exegesis. The author wears his erudition lightly and leavens his writing with reader-friendly anachronisms, likening Hildegard to blues chanteuse Bessie Smith and calling the Franciscans "the world's first hippies." The result is a fresh, provocative look at an epoch that's both strange and tantalizingly familiar.