When does an ideology become a political religion? That’s the question raised by last week’s confirmation hearing for Notre Dame law professor Amy Coney Barrett, a federal judicial nominee. When Ms. Barrett appeared before the Senate Judiciary Committee, the standard question-and-answer session quickly devolved into an interrogation of her Catholic faith.

“Dogma and law are two different things,” Sen. Dianne Feinstein (D., Calif.) lectured Ms. Barrett. “I think in your case, professor, when you read your speeches, the conclusion...