Book excerpt: "If you read Supreme Court opinions on cases involving First Amendment religion issues, you're likely to encounter the ubiquitous phrase "sincerely held religious belief." The "sincerity test" of religious belief has become a cornerstone of US jurisprudence, determining what counts as legitimate grounds for First Amendment claims in the eyes of the law. In Sincerely Held, Charles McCrary provides an original account of how "sincerely held religious belief" became the primary standard for determining what legally counts as genuine religion. McCrary traces the interlocking histories of sincerity, religion, and secularism in the US, starting in the mid-nineteenth century. He then shows how, in the 1940s, as the courts expanded the concept of religious freedom, they incorporated the notion of sincerity as a key element in determining religious freedom protections. The legal sincerity test was part of a larger trend in which the category "religion" became largely individualized and correlated with "belief." This linking of religion and belief, with all its Protestant underpinnings, is a central concern of critical secularism studies. McCrary contributes to this conversation by revealing the history of how sincerity and sincerely held religious belief developed as technologies of secular governance, constraining the type of subject one has to be in order to receive protections from the state"--