In 2012, the Hans Kelsen Institute in Vienna published Hans Kelsen's Secular Religion, a book he completed in the 1960s and then withdrew from publication for reasons that are by no means certain. The book is Kelsen's passionate defense of scientific reasoning as distinct from religious modes of reasoning. As noted in the book's subtitle, the work is Kelsen's polemic against those who would tame modern science and modern politics by treating both phenomena as engaging in modes of reasoning that are either the same as or analogous to religious modes of reasoning. The book's publication is especially timely because it comes in the midst of a vigorous debate in the U.S. legal academy, the courts and the public sphere about the extent to which religious belief is distinct from other forms of sincerely-held beliefs. The scope of protections for liberties protected under the U.S. Constitution's Free Exercise Clause could turn on our ability to understand religious beliefs as distinct from other systemic sets of belief.