I am a linear writer as well as a linear reader (though in suspenseful novels I sometimes look ahead and then get mad at myself for hitting upon some spoiler that I should have prevented myself from learning). So I would be perfectly happy if a reader started at Page 1 of the Introduction, which begins with a key insightful remark by Madison, given in 1822, noting how the experiment in disestablishment had allowed American religion to “flourish in greater purity” without having to rely on the aid of government.But I also like my own intriguing insight at the start of Chapter 1, “The Burden of Toleration,” that when one lives in a tolerant society, as we do, we no longer know what toleration, properly defined, historically meant.And Chapter 3 begins by speculating how the American ideas of religious freedom might have evolved had the Revolution not occurred. Of course, the Revolution did occur, and that in turn required Americans to begin writing new constitutions of government to replace their old colonial charters. Here I quote a passage from the reading notes that Jefferson compiled in the fall of 1776, when he first met Madison. Both men were serving on the religion committee of the Virginia House of Delegates and trying to figure out what position the new state should take on matters of religious liberty. Jefferson used the occasion to reread John Locke’s Letter Concerning Toleration, and his notes contain this trenchant remark: “It was good to go so far (as he himself says of the parl[iament] who framed the act of toler[atio]n [of 1689]; but where he stopped short, we may go on” [emphasis added].Asking what it meant for the Americans to “go on” is an underlying theme of the whole book, so this is also a nice point of departure.This book is part of the series, Inalienable Rights, edited by my friend and colleague, Geoffrey Stone, of the University of Chicago (which happens to be my literal birthplace). All the other contributors to this series are professors of law; I am the sole historian who is involved in the project. But I happen to think having a historical perspective on what has become a vexed area of jurisprudence has real intellectual advantages. Many legal observers regard Religion Clause doctrine as a mess, and that situation makes it difficult to appreciate what a great success the radical American departure embodied in the First Amendment has been.The basic fact remains, I believe, that Madison and Jefferson (and to some extent Madison more than Jefferson, as I explain in the book) were right: the more one does to enable individuals to be their own religious truth-seekers and to maintain a high wall of separation between church and state, the happier we will collectively be. This book does offer a short summary in its concluding two chapters of the leading issues of Religion Clause jurisprudence, though emphasizing “free exercise” more than disestablishment. But its real purpose is to provide a historical context for appreciating and, I hope, validating the American experiment in religious freedom.