Fundamentalist forms of religion today claim authority everywhere, including the debates over the politics and constitutional law of liberal democracies. This book examines this general question through its critical evaluation of a recent school of thought: that of the new natural lawyers. The new natural lawyers are the lawyers of the current Vatical hierarchy, polemically concerned to defend its retrograde views on matters of sexuality and gender in terms of arguments that, in fact, notably lack the philosophical rigor of the historical Thomism they claim to honor. The book critiques forms of fundamentalism and offers an original argument both for how they arose and why they are unreasonable in contemporary circumstances.