Tolstoy’s conversion account appealed to James on many levels, not least because churches and clergy played no role in it. Though James sometimes self-identified with Protestant Christianity, that label was accurate only in the narrowest cultural sense. Theologically, he was as heterodox as he was unsystematic—he theorized, for example, that there might be multiple deities. But if he was at most a marginal Christian, James was enthusiastically a Protestant. In Varieties, he pointedly reduced religion to its minimalist essence. “As I now ask you arbitrarily to take it,” he wrote, religion “shall mean for us the feelings, acts, and experiences of individual men in their solitude, so far as they apprehend themselves to stand in relation to whatever they may consider the divine.” This was unmediated Protestantism in its purest, most unfettered form.
Theo Anderson, One Hundred Years of Pragmatism
One can't help but wonder how much the Jamesian approach to religion has influenced First Amendment jurisprudence. Out of respect for Protestantism(respect I didn't even know I had), I must protest Anderson's characterization of Protestantism in terms of its most individualistic liberal form. It's not always that bad.
Nevertheless, Anderson's essay is an excellent complement to my current read, Louis Menand's The Metaphysical Club, a history of the American pragmatists with a talent for depicting the zeitgeist of late nineteenth-century New England.
Note that Anderson also intimates in James the beginnings of so-called therapeutic deism:
James’s writings contain glimmerings of the spirituality industry that would burgeon in the later 20th century. He posited other realms of consciousness and higher energies as agents of human “empowerment,” themes that have become ubiquitous among self-help authors. James likely would have deplored much of this genre, yet it is in some ways a logical outgrowth of his emphasis on the pragmatic consequences of faith. The ecumenism of the self-help genre is also quintessentially Jamesian: Spirituality is presented as an unmediated relationship between the individual and the divine. Institutions only get in the way.