Moral Life
The Moral Argument and Natural Law
Objective moral obligations that bind all people everywhere point beyond human convention to a transcendent lawgiver, and this natural law is written on the human heart and knowable by reason.
Catholic teaching
The Church teaches that the natural law is the participation of rational creatures in God's eternal law, expressing the dignity of the human person and forming the basis of moral obligations and rights. It is not invented by any culture but discovered, present in different formulations across civilizations, and it does not depend on religious belief to be binding, since it is inscribed in the human heart by the Creator and accessible through reason alone. Where genuine moral obligation exists—not merely social preference, but real duty that binds even against self-interest and cultural consensus—this points to a moral lawgiver, since an obligation implies someone to whom it is owed.
Biblical foundation
Paul teaches that even Gentiles who do not have the written Law show that the work of the Law is written on their hearts, their conscience bearing witness, accusing or excusing them—an explicit statement of natural law before any revealed code. The Psalmist praises God's law as more desirable than gold, showing that moral goodness is objectively attractive and rooted in God's own character, not human whim. Micah summarizes the moral requirement of God as doing justice, loving kindness, and walking humbly, a standard presented as binding on all, not merely on Israel.
Scripture references
Historical evidence
The natural law tradition runs from Stoic philosophers like Cicero, who spoke of a true law, right reason, agreeing with nature, diffused among all men, through the Church Fathers who baptized this insight, to St. Thomas Aquinas's systematic treatment in the Summa Theologiae in the 13th century, and it directly informed the framers of modern human rights documents, including the postwar Universal Declaration of Human Rights, which appealed to inherent human dignity as a check on state power—an appeal to a standard beyond any single nation's law, echoing the natural law tradition even in a secular forum.
The Church Fathers
“Whatever things were rightly said among all men are the property of us Christians... for all writers were able to see realities darkly through the sowing of the implanted word that was in them.”
“Thy law is written in the hearts of men, which iniquity itself effaces not.”