The respect for religious difference has formed the bedrock of our nation and made equality possible. Yet today we are told that “moral values”—code for a government shaped by religious concerns—must be the keystone of our social compact.

A rich and compelling chronicle of an essential idea, Liberty of Conscience tells the story of America’s great tradition of religious freedom. Philosopher Martha Nussbaum’s ambitious book is both a work of history and a pointed rejoinder to conservative efforts to break down barriers between church and state.