"First, it was Evangelical Christianity. Some of the radicalism they took from their faith. They took from the so-called Second Great Awakening. They took from this idea that somehow, it was their duty, it was their place in the world...to save souls...it was only one step further--and Finney told them that--to save society as well. And if conversion to Christ or conversion to faith, conversion to salvation, can happen immediately in a person, why not a whole society? If you can revolutionize a single soul, why can't you revolutionize a hundred, 100,000, 1,000,000?... We're living in a different kind of era of Evangelicalism in the United States--although some Evangelicals are indeed reformers, they tend to be seen today largely as political conservatives, social conservatives. Some of the Evangelicalism of the 1820s in America, in the 1830s, became a much more radical kind of Evangelicalism in terms of the social changes that they were advocating."
The false dichotomy between saving souls for another world and saving the world itself, was clearly not understood by nineteenth century evangelicals. Certainly, my research on the period confirms this and has revealed Christianity's relationship to slavery to having been a broadly positive one.