The Ground of All Morality: A Catholic Response to Moral Relativism

Introduction: The Modern Moral Dilemma

There is perhaps no question more fundamental to the human experience than this: What makes something right or wrong? In a recent discussion, a friend insisted that morality arises from "common sense"—from lived experiences, reasoning, and social consensus. But I pressed further: Where does that common sense come from? What gives it authority? If Hitler's genocidal logic was born from a particular society's education and values, then what prevents that form of "common sense" from being as valid as ours?

The Dissenter’s Objection: Morality Without God

The argument is often made that morality does not require God. People, the dissenter claimed, can reason their way to right and wrong. We value sentience. We are capable of empathy. Across cultures, there seems to be a shared disapproval of murder, theft, rape. This global "common sense" is cited as evidence of a natural moral instinct, akin to a kind of evolved social wisdom. Scripture, to them, is irrelevant; some even claim God's commands contradict modern morality, such as His regulations on slavery in the Old Testament or His toleration of child marriage in ancient cultures.

Clarifying the Claim: The Necessity of a Moral Anchor

Let us begin by affirming something we both agree on: some actions are objectively evil. Murder is wrong. Slavery is wrong. Genocide is wrong. But if that is the case, then morality cannot simply be the product of social consensus or evolutionary instinct. Why? Because those things change. Cultures evolve. Consensus shifts. And instinct, however powerful, is often contradictory.

Instinct may urge me toward adultery, but morality tells me to honor my partner. Evolution may reward dominance, but morality praises humility. If instinct and consensus are our only guides, then morality floats on a sea without a shore—directionless and ultimately meaningless.

The Logical Consequence: Without God, All Morals Are Preferences

If there is no God—no eternal, unchanging, omniscient source of moral law—then there is no such thing as moral obligation. You may feel something is wrong, but that feeling has no more authority than anyone else’s. The man who believes that rape is justified is not wrong—just different. Unless there is a higher law, beyond all of us, that judges us all equally.

If humans are simply evolved animals, and our behaviors are the result of neurons firing and instincts mutating over millennia, then how can you say murder is truly wrong? Harmful, perhaps. Inconvenient, sure. But wrong? Wrong according to what?

Scripture and the Moral Law

Scripture affirms this reality. In Romans, St. Paul writes:

Indeed, when Gentiles, who do not have the law, do by nature things required by the law... they show that the requirements of the law are written on their hearts.

— Romans 2:14-15 (NIV)

This law is not invented. It is discovered. It is not imposed. It is received. And it is written not just on tablets of stone, but on the human heart. The Church calls this the natural moral law:

Man participates in the wisdom and goodness of the Creator who gives him mastery over his acts and the ability to govern himself with a view to the true and the good. The natural law expresses the original moral sense which enables man to discern by reason the good and the evil, the truth and the lie:

The natural law is written and engraved in the soul of each and every man, because it is human reason ordaining him to do good and forbidding him to sin ... But this command of human reason would not have the force of law if it were not the voice and interpreter of a higher reason to which our spirit and our freedom must be submitted

— Catechism of the Catholic Church, no. 1954

This law is a participation in God’s own wisdom and goodness. It is the echo of the divine mind in the human soul. And without that divine source, all other attempts to explain morality fall short.

Answering the Objection: But Isn’t God Inconsistent?

Some argue that God Himself is not morally absolute. They cite Old Testament practices—slavery, polygamy, patriarchal laws—and ask how a perfect God could condone such things. But this misunderstands both Scripture and the nature of divine revelation.

God meets humanity where they are. In a fallen, violent world, He gradually elevates human morality toward His perfect law. As Jesus Himself said:

Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning.

— Matthew 19:8 (NIV)

The Old Testament is not a picture of moral perfection, but a story of moral progression, culminating in the person of Jesus Christ, who is the full revelation of God’s justice and mercy. The moral law is fulfilled in Him—not abolished.

The Moral Compass Always Points to Christ

All true morality points to Christ, whether we know it or not. He is the Logos, the reason behind reason, the source of every instinct toward love, justice, truth. When we say murder is wrong, we echo the heart of the One who gave His life for His enemies. When we say slavery is evil, we affirm the dignity of the human person made in the image of God.

The Church Fathers understood this. St. Justin Martyr, writing to the pagan emperor Antoninus Pius, argued that all who live according to reason live according to Christ—even if they do not yet know His name. And yet, to know Him fully is to have the law written not just on our hearts, but fulfilled in our lives.

Conclusion: The Light That Guides

Morality is not an accident. Our deepest intuitions—our love for the vulnerable, our revulsion at cruelty, our yearning for justice—are not the products of blind chance. They are reflections of the Divine, signs that there is something more.

Without God, you can have instinct, opinion, consensus. But you cannot have goodness. Not truly.

But with Him, morality is not a matter of preference. It is a matter of truth. And the truth is a Person.

I am the way and the truth and the life. No one comes to the Father except through me.

— John 14:6 (NIV)