As we have said, the law of marriage of Western Europe of the Middle Ages was canon law, and it was complicated. By the beginning of the thirteenth century, the period in which we first have records of runs of cases, it was the product of a continuous development of more than seven hundred years, with roots going back into Roman law, Judaism, and early Christianity, and the customs of the non-Roman peoples of the West. A particularly notable feature of this development was the extraordinary efflorescence of learning, teaching, and promulgating law that occurred in the twelfth century. As we have also said, the story of this development is the topic for another book. Here we must briefly outline the rules as they existed, or were thought to exist, in the early years of the thirteenth century. While the next three centuries saw some development of these rules, perhaps more than is normally thought to have occurred, the changes were subtle and, with the notable exception of developments in the law of separation with which we have occasion to deal in Chapter 10, they do not seem to have had much effect on marriage litigation in ecclesiastical courts, the focus of this book. Hence, the outline that we give here may be taken as the outline of the rules that the proctors, advocates, and judges of the courts with which we are dealing assumed, or should have assumed, as they presented and decided the cases that were brought to them.