The conjugal view of marriage, we argued, has long informed the law — along with the literature, art, philosophy, religion, and social practice — of our civilization. So understood, marriage is a comprehensive union. It unites spouses at all levels of their being: hearts, minds, and bodies, where man and woman form a two-in-one-flesh union. It is based on the anthropological truth that men and women are distinct and complementary, on the biological fact that reproduction requires a man and a woman, and on the sociological reality that children benefit from having a mother and a father. As the act that unites spouses can also create new life, marriage is especially apt for procreation and family life. Uniting spouses in these all-encompassing ways, marriage calls for all-encompassing commitment: permanent and exclusive.