Buckham's "Progressive Religious Thought in America" (1919) is a very useful survey of the development of "progressive" theology in Congregationalism and covers the leading figures in this denomination's move away from the Old Calvinist New England theology of Jonathan Edwards and his followers. Some of the figures Buckham covers—and he cites liberally from their own words—were leading scholars at Andover Seminary, which was rocked with the controversy between traditionalists and progressives. Notable is the way figures like Newman Smyth embraced new developments in the natural sciences (particularly biology and psychology) as well as biblical criticism. Buckham is an excellent guide to these figures and this movement, being himself very intimately acquainted with the persons involved as well as the their writings.