Knox was founded in 1837 by anti-slavery social reformers, led by George Washington Gale, and today ranks as one of the top private liberal arts colleges.

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It only serves about 30 people, but it's the beginning of efforts to deal with slavery's social impact -- by giving slaves job skills, an education, the tools to create a viable life if and when they escape from their masters.

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But perhaps his best chapter is on 19th-century America, where he distinguishes the reformers who prepared Christ's coming, as they saw it, by combating slavery, alcohol and other social evils, from the separatists, who withdrew into their own sects and cults, the better to wait out Christ's judgment on an unrescuable world.

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Yet, except in areas like that, bordering the Sahara, where blacks were traditionally enslaved by lighter-skinned desert peoples, slavery and the slave trade left no social stratification, and they figure little in popular consciousness today.

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Look at history, and you can see the religious left at the heart of America's great social-reform movements, from the fight against slavery to the New Deal to the civil-rights movement (for some reason, Prohibition is usually left off the list).

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From slavery to the civil rights movement, black social action offered the nation the opportunity -- and template -- for transforming democratic rhetoric into uplifting deeds that brought America closer to its founding principles.

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