Marriage in Europe became a central pillar of society during the medieval period. Theologians, lawyers, and secular and church leaders agreed on a unique outline of the institution and its legal framework, the essential features of which remained in force until the 1980s. The medieval Western European definition of marriage was unique: before the legal consequences of marriage came into being, the parties had to promise to engage in sexual union only with one partner and to remain in the marriage until one of the parties died. This requirement had profound implications for inheritance rules...