The soaring modernist chapel at the Air Force Academy in Colorado Springs, built in 1962, was intended to symbolize America's embrace of religious diversity and interfaith harmony: different spaces for Protestant, Catholic and Jewish services each "accommodat[ed] within a single enclosure," as one architectural review put it.  Alas, the design's messages about religious equality were decidedly mixed. The Protestant chapel not only had 12 times the seating capacity of the Jewish chapel and nearly three times that of the Catholic, but it also occupied the 100-foot-high, cathedral-like main vault, while the Catholics, Jews and others were allocated to lower-level rooms with regular ceilings.

The story of the Air Force chapel is one of many vignettes in William R. Hutchison's rich and engaging book on the "contentious history" of religious pluralism in America. Hutchison, the distinguished Harvard historian, sees the story as a process of making good on the "promissory notes" of religious equality guaranteed in founding documents like the First Amendment and Jefferson's Virginia Statute for Religious Freedom. Although Hutch­ison thinks that the promises have been substantially redeemed over 200-plus years, he emphasizes that the process has been slow and halting.

After defining the ideal of pluralism as "the acceptance and encouragement of diversity," Hutchison posits three chief stages through which the meaning of religious pluralism expanded in America. At first pluralism meant mere toleration, permitting various groups outside the Protestant mainstream the right "to exist and even to thrive," but according them no role in defining the culture—and repressing them if they ventured too far from the mainstream. Analyzing the anti-Catholic Know-Nothing movement of the 1850s and the anti­polygamy crusade against Mormons during ensuing decades, Hutchison argues that the bounds of acceptability were defined primarily by behavior; one could believe pretty much anything as long as one refrained from "socially threatening" conduct.