The relationship between religion and the state remains contentious. Religious differences continue to be a major source of tension and sometimes violence across the world. Even in liberal democracies there are frequent disagreements about the scope of religious freedom. Do states have the right to regulate religious clothing? Can the state prohibit religious organizations from discriminating against individuals who do not share their beliefs? Should states fund religious schools? How stable are institutions that support religious liberty?

We do not provide direct answers to all of these questions. Rather, we argue that to tackle issues such as these we first need to know where our modern notions of religious freedom come from. This requires an understanding of the processes that governed the emergence of religious liberty. It requires not just a knowledge and understanding of history, but also an appreciation of the political and economic challenges that confronted premodern states. This is what we provide in this book.

Doing so requires confronting several popularmyths that have grown up around the subject of religious toleration. The first myth is that religious violence was ubiquitous in medieval and early modern Europe. This claim is repeated in popular histories and is sometimes accompanied by the claim that other parts of the world such as Islamic Spain, the Middle East, or the Mongol Empire were comparatively tolerant. Books and films have shaped a widely held view of theMiddle Ages and early modern period in which we are led to believe that the execution of heretics and witches was an everyday occurrence. This reflects the influence of novels like Umberto Ecco's The Name of the Rose and less edifying forms of entertainment such as the 2010 film Black Death starring Sean Bean. These popular depictions of medieval Europe suggest that religious persecution was an ever present feature of life in the past. In many respects, this is a reassuring image. At least in the West it allows us to view religious violence as the product of intolerant and superstitious individuals.

But were people in medieval Europe, in fact, more prone to persecute religious minorities? An alternative view is that medieval Europeans, like all people, responded to the incentives generated by the institutions that surrounded them. Religious persecutions did not reflect fanatical or irrational beliefs. Rather, they reflected the political economy of the premodern world, in which rulers depended on religious authorities for legitimacy.