The Vatican On November 25, 2025 issued a landmark doctrinal decree, approved by Pope Leo XIV, reaffirming that for members of the Catholic Church, marriage must be a lifelong, exclusive union between one man and one woman.
The decree, titled Una caro “One Flesh” restates the church’s traditional teaching on the unity, indissolubility and exclusivity of marriage.
At its core, the document emphasizes that “every authentic marriage is a unity composed of two individuals, requiring such an intimate and totalizing relationship that it cannot be shared with others.”
According to the Vatican’s doctrinal office, only two people can give themselves fully and completely to each other, any attempt to include more than two diminishes the integrity of the union and fails to uphold the dignity of each partner.
The decree also comes in response to two trends observed by the church worldwide.
First, it addresses the continued prevalence of polygamy in some regions, particularly sometimes conflict with Catholic teaching. Second, it responds to the rise of polyamorous relationships and non-monogamous partnership in parts of Western society.
In its theological argumentation, “Una caro” draws on Scripture, Christian tradition, philosophy, and even poetry to defend monogamy. The document asserts that monogamous, lifelong marriage reflects the original intention of human union; a sacramental bond rooted in mutual belonging, fidelity, and shared dignity.
Importantly, the focus of the Note is not only on procreation. While openness to children remains part of Catholic marriage, the Vatican makes clear that sexual union and conjugal love are not merely biological or utilitarian, but deeply relational, unitive, and capable of expressing love, respect, and commitment even in childless unions.
The document portrays monogamy not as a constraint or limitation, but as “a promise of the infinite”, a lifelong commitment in which two people entrust themselves to each other completely, in fidelity and mutual belonging.
Through this decree, the Vatican is clearly reasserting its position on marriage at a time when evolving social norms, such as polygamy, serial relationships, and polyamory, challenge traditional views.
For Catholics worldwide, the message is direct: marriage is intended to be an exclusive, irrevocable union between one man and one woman, grounded in love, dignity, and lifelong commitment.
