Mullen suggests attention should especially be paid to the non-eliete irreligious, if possible. He writes:
Irreligion was far more widespread than just among elites. If we trust work on the historical demography of American religion ... then there is reason to think that American religious history has neglected a lot of people. Simply put, if religion and specifically groups like Methodists, Baptists, and Catholics were growing constantly, and not just from immigration, then they had to grow from somewhere. Who were these secularists or 'nones'? The nineteenth century has bequeathed us competing explanations. The secularist explanation was that the more education one possessed, the further back one had pushed the superstitions of religion. Perhaps -- but only post-Darwin, and then only for elites. Much more persuasive is the shared assumption of Protestants, Catholics, and Jews that ignorance produced irreligion. Many of the vast nineteenth-century evangelistic enterprises, such as the Sunday school (Jewish as well as Christian), the Confraternity of Christian Doctrine, the evangelical tract and textbook, and for that matter the public schools, were fundamentally educational. To hear Peter Cartwright tell it, he was constantly encountering (and wrasslin’ with) “rowdies” and skeptics. When colporteurs of the American Tract Society sold Bibles in the Pine Barrens of New Jersey in the 1840s, they found many people who, they claimed, “had never heard of Jesus Christ.” What would a religious history of those people look like?The post also offers and excellent overview of the historical works currently available on American atheist, agnostic, freethinking, humanist, and ethical culture movements, and highlights a few things that are in the works.