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Faith and reason testify to each other

Friday, February 13, 2026Spirituality

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The Ten Commandments were revealed. But they were known before they were revealed: Why else did Cain hide when he killed Abel?

Michael
Pakaluk

When St. Pope John Paul II wrote in his great encyclical, "Fides et ratio," that "Faith and reason are like two wings on which the human spirit rises to the contemplation of truth," he surely meant that faith and reason are complementary not simply in how they act but also in what they say.
What do I mean? They are complementary in how they act: a stronger faith clarifies our reason, and surer reasoning fosters a surer faith.
But also in what they say: faith tells us, in faith, that it is not sufficient; while reason tells us, in its stringency, that on its own it falls short, so that faith must enter in also.
They testify to each other. Faith witnesses to reason, and reason witnesses to faith.
Consider the truth that God exists. Faith tells us that, by reason, we can be confident that God exists: "Ever since the creation of the world his invisible nature, namely, his eternal power and deity, has been clearly perceived in the things that have been made," (Rom 1:20). So St. Paul tells us, on his authority. This verse teaches something about human reason, but it is not itself a sample of human reasoning. To receive this teaching on the Apostle's authority is to receive in faith that reasoning has its role here.

But faith as articulated in Sacred Tradition also testifies to reason. The First Vatican Council, relying on that verse from St. Paul, and also on the faith of the Church over the centuries, taught as a matter of faith for Catholics: "If anyone says that the one and true God, our Creator and Lord, cannot be known with certainty, by the light of natural human reason, through the things that are made, let him be anathema" ("Dei Filius").
It was important for the council to insist on reason's ability here, to counteract the various forms of sentimentalism and fideism which were prevalent then. (This "Modernism" is equally prevalent now.) Otherwise, faith is destroyed, no matter what we think or say. The belief in God's existence is one of those famous "preambula fidei": it is a necessary step to having faith. Why? Because to have faith is to accept what God, a living person, says. But how can you believe in a person, if you do not believe that he exists?
Suppose that a man on a desert island receives a bottle with the message, "Believe me, I am coming to help you," and as a result the stranded man believes that someone is coming to help him. Yet, he believes in the existence of this savior because he supposes that the writing and the message and the bottle must have a cause, not because of what the message declares.
Many Protestants affirm the "total depravity of reason" and Luther's "reason is a whore." (I know I did, as a Protestant.) For such persons, a crucial step in becoming Catholic may be to reject the irrationalism which affects their faith -- when they accept as true, in faith, this vital teaching of the Catholic Church.
And yet reason's having a role in any matter of faith ought to be equally decisive against the "total depravity of reason."
Faith extends to matters of morality as well as matters of belief. Does faith testify also to the role of reason in morality? Where does Scripture or tradition testify that there is a "natural law?"
Once again, St. Paul is the great authority: "When Gentiles who have not the law do by nature what the law requires, they are a law to themselves, even though they do not have the law. They show that what the law requires is written on their hearts," (Rom 2:13-14). They "have not the law;" that is, no law has been revealed to them. If, then, they believe and follow, "Do not steal," it is because by reason they acknowledge that they ought not to steal.
It's not that each Gentile receives a private revelation, a voice inside his mind enunciating the Ten Commandments. St. Paul's language precludes such an interpretation. "They are a law to themselves" must mean that they themselves directly formulate the Commandments.
The Ten Commandments were revealed. But they were known before they were revealed: Why else did Cain hide when he killed Abel? Besides, each implicitly testifies that reason must have a role. The commandment, "Thou shalt not steal," implies that we already can recognize what Leo XIII called "the natural right to private property." To mark out anything as mine or yours is to mark out what ought not be stolen.
Or how can "be perfect, as your Heavenly Father is perfect" (Matt. 5:48) have any purchase unless we already have the ability to recognize perfection, virtue, and excellence? Jesus presupposes that reason has this power.
Or how would it make sense to say "Let your light so shine before men, that they may see your good works and give glory to your Father who is in heaven" (Matt. 5:16), unless men can already recognize good deeds, distinguish them from bad, and praise the good ones?
Reason is a natural endowment, and faith a supernatural gift. By attending with care to how these work together, like the wings of a dove, we may come to value each, the way the other tells us to value it.

- Michael Pakaluk, an Aristotle scholar and Ordinarius of the Pontifical Academy of St. Thomas Aquinas, is a professor in the Busch School of Business at the Catholic University of America. He lives in Hyattsville, MD, with his wife Catherine, also a professor at the Busch School, and their eight children. His latest book is "Be Good Bankers: The Economic Interpretation of Matthew's Gospel.'' You may follow him on Substack at MichaelJosephPakaluk.Substack.com.