This book contributes to a better understanding of the mysterious reality of marriage in the long-standing Judeo-Christian tradition, which acquired singular force in light of Saint John Paul II’s theology of the body. It does so by examining the doctrinal tensions that arose with the related development of theology and canon law throughout the Middle Ages and modern period. Saint John Paul II’s recovery of the centrality of the una caro has restored the primary meaning of marriage, thus renewing the hope of recovering the ultimate meaning of history as the full realization of what is human. Therein, conjugal love according to God’s plan expresses and fulfills Christianity’s three munera, which are priestly, prophetic and kingly. The thesis contained herein sheds light on a new and more fruitful foundation for the social sciences, one that looks not to the individual, but to marriage and its practical realization in the family, that is, to the community of people at the heart of the social system. This foundation allows humankind to express our true royalty, which is ultimately found in serving others towards the realization of the common good.