Thomas D. Hamm Ph.D. (1985), is Professor of History and Director of Special Collections at Earlham College in Richmond, Indiana, where he also holds the Trueblood Chair in Christian Thought. His works include The Transformation of American Quakerism (Indiana University Press, 1988), and, mostly recently Quaker Writings: An Anthology, 1650-1920 (Penguin Classics, 2010).

A self-conscious liberal Quakerism emerged in North America between 1790 and 1920. It shared three characteristics: commitment to liberty of conscience; questioning of Christian orthodoxy; and an insistence that liberalism was a continuation of historic Quakerism.