Fast-forward to March 2014, when the Court heard arguments in another case about religious dissenters from general laws: Sebelius v. Hobby Lobby Stores, Inc.—probably the most important case of the term, and a revealing capstone in Scalia’s jurisprudential career. Nobody that day dreamed of questioning the religious beliefs of the arts-and-crafts chain’s Christian owners, who were seeking exemption from the Affordable Care Act mandate to provide insurance coverage for birth control. Certainly the justices on the left wing of the Court and the Obama administration didn’t: whatever science, medical consensus, or neutral law may say on the subject of abortion-causing drugs and devices, the government wasn’t about to challenge Hobby Lobby’s belief that particular forms of birth control cause abortions (or to note that the business, even if inadvertently, once covered the same contraceptive methods its owners abhor). Nor was Scalia, who this time—in a dramatic about-face from his 1990 position—clearly supported the religious objectors. In fact, in the course of grilling the lawyers, he blurted out what sounded like agreement with the plaintiffs’ claims that these items were abortifacients. The spectacle was enough to make one wonder, quietly: Peyote didn’t sway him, but what about his own brand of piety?

A version of Scalia’s question about the inscrutability of religion back in 1990 can be asked about him: What principles or empirical approach can be brought to bear to evaluate the justice’s heartfelt assertion that no act of his on the Court is ever grounded in his personal faith? In Bruce Allen Murphy, Scalia has met a timely and unintimidated biographer ready to probe. A professor of civil rights at Lafayette College, Murphy refuses to be daunted by the silence that surrounds most discussions about religion and the Court. In his view, understanding one of the most dazzling and polarizing jurists on the Supreme Court entails, above all, examining the inevitably murky relationship between judicial decision making and religious devotion.

In Scalia: A Court of One, Murphy painstakingly reviews the evidence, much of which lies in Scalia’s own writing and speeches over many decades, going back to his college commencement address at Georgetown University. Murphy does not shrink from adjudicating Scalia’s dueling public claims: that separating faith from public life is impossible and, at the same time, that he himself has done just that on the Court. Murphy’s conclusion—at once obvious and subversive—is that Justice Scalia is very much the product of his deeply held Catholic faith. The pristine border between faith and jurisprudence is largely myth and aspiration.

Scalia certainly presents a stark puzzle. On the one hand, he wears his Catholic loyalties on his sleeve. Born in Trenton, New Jersey, in 1936, he was a brilliant only child whose mother was a teacher and whose Italian immigrant father was deeply intellectual and conservative. Early on, Scalia embraced a hero Murphy frequently invokes as a historical comparison: Thomas More, who refused to sanction the annulment of Henry VIII’s marriage to Catherine of Aragon and died a martyr for his religious principles. Already in his Georgetown commencement address, in 1957, Scalia was urging his classmates not to separate their religious life from their intellectual life. “If we will not be leaders of a real, a true, a Catholic intellectual life, no one will!” he said. “The responsibility rests upon all of us whatever our future professions.”