Mullen then shifts his focus to Christians who changed their allegiances, concentrating primarily on Mormonism. While individuals in the Protestant mainstream saw Mormonism as a new, anti-Christian religion, converts to this movement saw themselves as restoring the ancient Christian faith. Not only did Mormonism provide Americans with yet another religious option, it allowed converts to express that choice through a number of rituals. The key ritual was baptism, which was the mark of Mormon conversion. This practice was highlighted in the Book of Mormon, which spoke explicitly of religious faith as choice. By the late 19th century, Mormons had been pushed to the geographic margins of America, but according to Mullen, in terms of their emphasis on conversion and religion as choice, they were well within the mainstream.
While missionary efforts had been successful among the Cherokee, they made less headway among Jews in the United States. Within Judaism, conversion (whether into the faith or out of it) was most common when religious intermarriage occurred. In both cases, the sincerity of the convert was key. Jewish converts to Christianity “had to conform to the requirements of heart religion,” while Christian converts to Judaism had “to meet the test of their motives required by the halakah,” the Jewish Law. The sincerity and motivations of converts were constantly called into question when they left one religion for another. This was especially true of American Jews who were constantly encouraged to convert and therefore had to “continually justify their refusal.” In this way, although relatively few Jews converted to Christianity, their Jewish religious identity increasingly rested less on habit or tradition and more on conscious choice.
The dizzying array of religious options in the 19th century led some Protestants down the path to Roman Catholicism. Dissatisfied with the endless variety of Protestant denominations, they chose a faith tradition that seemed to reject this pluralism. These “yearnings for catholicity,” as Mullen puts it, were satisfied in the Catholic Church. Catholicity appealed primarily to two groups: those closest to Roman Catholicism, such as members of the Episcopal Church, and those farthest away, such as members of liberal Protestant denominations. By embracing Catholicism, these converts were attempting to reject the whole system of religious choice in America, instead finding comfort in the unity, universality, and tradition of the Catholic faith.