The doctrinal note Una Caro (“One Flesh”): In Praise of Monogamy, issued by the Dicastery for the Doctrine of the Faith, on 25 November 2025, offers a timely and profound reflection on the significance of monogamous marriage as “exclusive union and mutual belonging.” In today’s world, marked by strong individualism, consumerism, and increasingly fluid ideas of relationships, the Church seeks to reaffirm the beauty, dignity, and theological depth of monogamy. The document arises both from pastoral concerns in regions where polygamy remains culturally present and from the rise of non-monogamous models in Western societies, including polyamory. It aims to help young people and couples rediscover marriage as a vocation of responsibility, fidelity, and trust.
Biblical Foundations
The Note grounds monogamy in Scripture, beginning with Genesis 2, where God recognizes that “it is not good for man to be alone.” The creation of woman introduces a partner who stands “face to face” with man, capable of reciprocal and personal communion. The biblical expression “they shall become one flesh” indicates a total, exclusive bond that encompasses body, heart, and life. Although the Old Testament includes examples of polygamy, the prophetic writings reinterpret God’s covenant with Israel in spousal terms, emphasizing exclusive fidelity. The Song of Songs celebrates unique, reciprocal belonging, “My beloved is mine and I am his”, while New Testament teachings, especially Jesus’ appeal to “the beginning” and Paul’s theology in Ephesians 5, reveal marriage as an icon of Christ’s faithful love for the Church.
Theological and Historical Development
Across Christian tradition, monogamy has been understood as the deepest expression of marital communion. Church Fathers such as John Chrysostom, Augustine, and Tertullian emphasized the unity, fidelity, and shared journey of husband and wife. Medieval theologians like Thomas Aquinas and Bonaventure saw marriage as an ontological union established by consent and consummated through bodily unity. Modern thinkers including Dietrich and Alice von Hildebrand enriched the Church’s understanding by highlighting the interpersonal dimension of marriage: loving the other as a unique, sacred “thou.” Contemporary theologians, such as Balthasar, Rahner, and several other writers, connect marital unity with the mysteries of Christ and the Trinity. Marriage becomes a participation in divine communion, where mutual belonging mirrors God’s self-giving love.
Magisterial Teaching
The Note traces how various popes and Church councils have consistently taught monogamy as intrinsic to Christian marriage. Leo XIII linked monogamy to the dignity of women and to mutual love that reflects Christ’s covenant with the Church. Pius XI’s Casti Connubii highlighted conjugal love and mutual sanctification as essential aspects of marriage. Vatican II and subsequent popes reinforced this vision, presenting monogamous love as a partnership of life, rooted in total self-gift and strengthened by grace.
Central Themes
The Note emphasizes two key elements:
- Reciprocal Belonging - Marriage creates a unique covenant in which husband and wife give and receive each other completely and exclusively. This belonging is not possession but a freely chosen, dignifying gift.
- Conjugal Charity - Marital love is a form of Christian charity that integrates affection, sacrifice, and mutual help. It inspires openness to life and solidarity with others, especially the poor.
Relevance Today
Addressing modern challenges such as unstable relationships, emotional fragility, and the rise of non-monogamous arrangements, Una Caro invites young people to rediscover love as commitment and responsibility. It also condemns all forms of violence, physical, psychological, sexual, or economic, within marriage. Ultimately, the Note presents monogamy not as a limitation but as a path to human flourishing, spiritual depth, and authentic love.
