For 16 words that remain completely unchanged from their adoption some 215 years ago, the Supreme Court's interpretation of the Religion Clauses of the First Amendment of the United States Constitution have shown remarkable malleability. Arguably, the court's interpretation of these Clauses has changed more often, and more dramatically, than of any other provision of the Constitution. The question I wish to explore is why. To address this question, we must put aside the standard interpretive perspective on constitutional law – the perspective that asks how constitutional provisions should be interpreted, in light of text, original meaning, history, or precedent. Those considerations do not change, at least not rapidly or radically. Instead we must ask how changes in cultural and social conditions have affected the jurisprudence of religion and state.

The First Amendment's Religion Clause consists of two parts. One, the Free Exercise Clause, prevents the government from prohibiting or punishing the profession and practice of any religion. Its counterpart is the Establishment Clause, which prevents the government, at a minimum, from designating any particular religion, articles of faith, or mode of worship as preferred or orthodox, and from compelling any person to participate in or support religious worship. Beyond these clear indications, there has been nearly continual controversy in the United States regarding such issues as: does the Free Exercise Clause protect religiously motivated conduct, such as the practice of polygamy or the refusal of priests to divulge the secrets of the confessional, from neutral and generally applicable laws?