The relations among nature, reason, and revelation are mysterious for both Protestants and Catholics. Consider John Paul II’s remark that “the primary and definitive source for studying the intimate nature of the human being is the Most Holy Trinity.” Read carelessly, this might seem to imply the utter futility of philosophizing about the constitution of the human person; nothing would be left but ­theology.

Not so, for revelation shines at least five different kinds of light on nature. First is the light of precept : God commands or forbids something that the mind itself can recognize as right or wrong. Certain moral matters are so obvious that at some level everyone already knows them”the wrong of adultery, for example, and the wrong of theft.

Of course, this raises the question: If we already know them, then why is God’s precept necessary? In one sense, it is impossible to be mistaken about these fundamentals; they are right before the eye of the mind. And yet, as Thomas Aquinas remarks, “they need to be promulgated, because human judgment, in a few instances, happens to be led astray concerning them.”

It is in this context that Thomas mentions the ancient Germans, among whom, he says, “theft, although it is expressly contrary to the natural law, was not considered wrong.” Thomas’ source, Caesar’s commentaries on the Gallic War, shows that what he had in mind was the Germans’ approval of stealing from tribes other than their own. These barbarians were “led astray,” however, not because they were ignorant of the wrong of taking what properly belongs to one’s neighbor but because they refused to recognize the members of the other tribes as neighbors. They didn’t justify theft; they told themselves that they weren’t really thieves.

This is the way a philandering man excuses his affairs. Perhaps he tells himself that he isn’t really unfaithful to his wife, because his lies keep her from being hurt. Or perhaps he tells himself that the question of faithfulness is complicated, because the other woman is more truly his wife than his wife is. He ­doesn’t justify adultery; he tells himself he is not really an adulterer.

The divine reminder of what we already know has a tendency to clear the mind. It confronts us, and the confrontation cleanses not only the individual but an entire culture. With our favorite evasions burned away, we think more clearly.

Precept not only confronts us. It also corrects us. Within the mind’s capacity for discovery, there are a great many points of morality that, after reflection, wise people consider obligatory. These have to be explained, however, to those who lack wisdom. In fact, even the knowledgeable may make mistakes. The wrong of adultery is obvious, even to the adulterer. But the good of chastity is not so obvious. To most people it seems rather a stretch. They may consider it admirable”a remote, ideal beauty”but it is unlikely to strike them as obligatory.

The difference should not be overstated. Are people completely ignorant of the moral character of chastity? Probably not. Even today, most people involved in sexual sin recognize its impurity more clearly than they let on. But they may not see the depth of the problem. An element of honest ignorance mingles with the element of denial, and God’s revelation does more than admonish us that we know better. It corrects the error, steadies the wandering judgment, and imparts certainty.

The correction of one vice has consequences for other vices and ultimately for our grasp of all natural law. In order to be deceived about the good of chastity, a man must also be deceived about a range of other goods. The truest friendship is partnership in a good life; in that respect, his friendship is impaired. Justice requires acute perception of what is really due to the other person; in that sense, his justice is impaired. Courage requires not just fearlessness but a right estimate of what things are worth fighting for; in that sense, his courage is impaired. Unfaithfulness requires constant deception; in that sense his frankness is impaired. As he is deceived in so many ways, his wisdom is askew. Insofar as wisdom regulates all of the moral virtues, the pattern of his life is askew.

When God reveals the precepts that the mind itself can recognize as right or wrong, we are confronted and corrected. We are also invited . Pondering the structures of creation, we can discern the fittingness of the revealed precepts.

Reflection on the reasons for God’s commandments was one of the great projects of rabbinical Judaism. Rabbi Saakyah Gaon declares that, if all relied on theft instead of work for livelihood, “even stealing would become impossible, because, with the disappearance of all property, there would be absolutely nothing in existence that might be stolen.” In similar fashion, Maimonides says that the eating of flesh torn from living animals”a violation of the Noahide commandments”“would make one acquire the habit of cruelty,” and Rabbi Hanina explains about the commandment to administer justice that “were it not for the fear of it, a man would swallow his neighbor alive.”

Such arguments seem to presuppose what they are trying to prove, but the circle is not vicious; the longer we reflect, the deeper we are able to go. Consider, for example, Rabbi Gaon’s remark. Constant theft leaves nothing that might be stolen, since no one will take care of what might be gone tomorrow: Without personal care and responsibility, the common good suffers. And so with the precepts of chastity. Without revelation, we may or may not have arrived at them. But once their revelation is accepted, the mind goes on to ask what makes them true. In other words, we ask what it is about our constitution that makes sexual purity so crucial and impurity so catastrophic.


Another supernatural light on nature is the light of affirmation . Affirmation is not a command to do or not do something, but a declaration that something is or is not the case. Conjugal sexuality, for example, is illuminated by the light of affirmation in the Book of Malachi: “Has not the one God made and sustained for us the spirit of life? And what does he desire? Godly offspring. So take heed to yourselves, and let none be faithless to the wife of his youth. For I hate divorce, says the Lord the God of Israel, and ­covering one’s garment with violence, says the Lord of hosts. So take heed to yourselves and do not be ­faithless.”

If the intellect concedes Malachi’s claim that sexual powers have a procreative purpose, then the logic of the rest of his argument is not hard to work out. After all, marriage is the only form of association in which the family-building aim of the sexual powers can be adequately realized. If a couple should say, “But we never meant to have children,” we should not think that they have a different, dissoluble kind of marriage but that they do not have a marriage. What they have is an affective liaison characterized by sexual intercourse outside of the conditions that allow the purpose of such intercourse to be fulfilled.

As I say, all this follows if the intellect concedes that sexual powers have a procreative purpose. But should reason concede this? In modern times, we tend to object that the purposes of things aren’t natural, that they are merely human constructs. The notion that nature is purposeful is derided as “metaphysical biology.”

Of course, we typically say this only about sex. The purpose of respiration is to oxygenate the blood; apart from it there would be no reason to have lungs. The purpose of circulation is to deliver nutrients and other substances to the places where they are needed; apart from it there would be no reason to have a heart and vascular system. If we are consistent, we should reason this way about sex, too. We should say that its purpose is to generate posterity; apart from this purpose there would be no purpose for the sexual organs.

Instead, we interrupt the argument to say that the purpose of sex is pleasure. On its face, the claim is absurd. Of course, sex is pleasurable, but pleasure accompanies the exercise of every voluntary power: Eating, breathing, even the stretching of muscles. The problem is that eating is pleasurable even if I am eating too much, breathing is pleasurable even if I am sniffing glue, stretching the muscles of the leg is pleasurable even if I am kicking the dog. For a criterion of when it is good to enjoy each pleasure, one must look beyond the fact that it is pleasurable.

One must look, in truth, all the way back to the Bible’s prime example of affirmative illumination: “So God created man in his own image, in the image of God he created him; male and female he created them.” Although the fact that we are made in his image exceeds unaided reason’s power of discovery, the things that are true about us because we are made in his image do not exceed it. So, for example, if God is personal, and we are his image, then it pertains to our essence that we are personal, too. And if two kinds of personal reality are required to image him”male and female”then male and female must complement each other not just in gross anatomy but in the root of their personhood.

Revelation interrogates reason. It asks, “Now that I point it out to you, can’t you see for yourself that your fundamental reality is personal?” This stirs us to penetrate still more deeply into personhood, and, through even longer reflection, we finally come to see that an individual man or woman is a complete individual reality, existing in itself, separate from all other things, made for rationality, the ultimate possessor under God of all it is and does. It is not just a piece or part of something; it is not just an instance or process of something. Nor is it merely a thing to be owned, a thing to be used, or a thing of any sort whatsoever. A person is not just a what but a who .

This insight has transformed the Western world, but there is more. Revelation goes on to ask: And can you not see for yourself that your two kinds of personal reality, male and female, depend on each other”that neither can be understood in isolation?

It would be impossible to overstate the depth of this affirmation or the abyss of the error from which it saves us. Personhood is incommunicable; I cannot transfer the mystery of who I am to another person. Unfortunately, it is all too easy to leap from this true statement to the mistaken conclusion that, because I am complete in a certain sense, I must be complete in every sense”that, because I cannot transfer myself, therefore I cannot give myself; that the incommunicability of persons precludes the communion of persons.

That would be bad enough, but, in a fallen world, the difference of sex deepens the error. To the mutual alienation of human and human is added the further disaffection of men and women. They come to seem adverse to one another, natural enemies like fox and bird, sundered by difference in kind. Revelation stays the error, showing that the reality is the other way around. If it takes both kinds of us to image our ­Creator, then our two kinds of personhood presuppose each other, and everything about us is made for ­communion.

The antecedent part of that statement, the if, goes beyond what unaided reason could confirm: Just as we need revelation to see that we image God, so we need revelation to know in what mode we image him. But the consequent part of the statement, the then, lies entirely within reason’s powers: Once it is called to the intellect’s attention, I can see that I am a whole person, yet I also perceive that I am not complete in the further sense that I could know myself if estranged from the opposite sex. Because I exist in myself, therefore I can give myself; if I were not a person, I would be incapable of gift.


A third light by which revelation illuminates nature is narrative : We learn more about natural law by thinking about the story. God differs from human authors in that, by his infinite power and wisdom, he arranges and orchestrates not just words but real things. Consequently, although the literal sense of the revealed narrative is deeply important, it falls infinitely short of exhausting its meaning. Certain correspondences occur between earlier and later stages in salvation history. Others occur between lower and higher things. Still others occur between events outside us and events within us. If God is not only the author of history but the lord of creation, then he can also orchestrate correspondences between events in the biblical story and truths about human nature. Narrative illumination is this sort of correspondence.

Consider again the great passage in Genesis: “So God created man in his own image, in the image of God he created him; male and female he created them.” Reading it in the light of affirmation, it says, “We are made like this.” But reading it in the light of its place in the narrative, it says, “ And then we were made like this.” In other words, instead of viewing it as a statement about what is the case, we can view it as the report of an event, which we relate to other events: Yes, we were created in such and such a fashion, but then we fell.

The Fall does not deprive us of our nature”a broken foot still has the nature of a foot”but our nature is not in its intended condition. For natural law, this is no insignificant consideration. If we had never seen healthy feet, it might have taken us a long time to discover that broken feet were broken”to reason backward from their characteristics in their present broken state to the principles of their design and to the fact that they deviate from that design. We might therefore take their broken state as normative. Even if we grasped that something was wrong with our feet, we might have misunderstood what it was. We might have thought that feet are evil by nature, or that they are good but corrupted by shoes.

In our times, the most spectacular attempt to discern what the narrative as narrative tells us about human nature is the series of general audiences that John Paul II published as Theology of the Body , which takes its departure from Christ’s reply to the question of why Moses permitted divorce: “For your hardness of heart Moses allowed you to divorce your wives, but from the beginning it was not so.” With great force, Christ’s answer redirects attention to the account of our origins in Genesis. Taking the cue, John Paul draws insights into our nature from three crucial aspects of the revealed narrative: Original unity, original solitude, and original nakedness.

Consider only what he says about original nakedness. These days carnality is underrated. Our obsession with sex doesn’t show that we take embodiment seriously; it shows that we don’t. Like Gnostics, we regard our bodies as separate from our true selves. We use them merely to get pleasure, attention, and other things for the self”and nothing taken seriously is merely used. But the Gnostics were wrong. As John Paul emphasizes, body is not separate from self; it is the emblem and vesture of self. The body is the visible sign by which the invisible self is actually made present, the medium of the language that it speaks. We mean things to each other by what our bodies do, and, when the speech of the mouth contradicts the speech of the body, the latter abolishes the former. Bone speaks to bone, mouth to mouth, flesh to flesh. To crush your windpipe with my thumbs is to say, “Now die,” even if I tell you with my mouth, “Be alive.” To join in one flesh is to say, “I give myself,” even if my mouth shapes the words, “This means nothing.”

Bodily speech is just as complex as vocal speech. Just as we can say inconsistent things with the spoken word, so we can say inconsistent things with the embodied word. The important thing to remember is that, even so, certain meanings are embedded in the language of the body. When you kiss to betray, you are certainly contradicting the primordial meaning of affectionate greeting, but you have not abolished it. When you employ a contraceptive barrier during sexual intercourse, you have not erased the meaning of sex, but you have overlaid it. Over the inscription “I join without reservation,” you have scribbled “but I withhold.”

Self-giving, moreover, is decisive. When I give a thing external to myself, I can set a term for it, after which I will take it back. When I give my very person, I give away the power of taking back; there is no authority left to revoke it. Totality and indissolubility turn out to be inherent in the meaning of the mutual gift by which marriage is physically consummated.

Even now we quibble. I may claim that a nanny, a day-care worker, or a bureaucrat can care for the child better than his parents can, or that it is better to have no parents than quarreling ones, or that a Mom can be a Mom, Dad, Grandma, and Grandpa, all rolled into one. Or I may claim that only so-called free love is real love, or that the language of the body is merely conventional, or that there is no such thing as a gift of self.

The argument seems never to end. The problem is that our willingness to grasp the refutations is all too easily undermined by sexual greed, weakness of will, evil habit, vicious custom, and depraved ideology. Even though the natural realities of marriage are fully knowable by unaided reason, they may not be fully known by it. The narrative of revelation is the key to forcing the mind to see the natural truth.


The fourth light that revelation shines on nature is divine promise . Two revealed promises are especially important. The first is the promise of forgiveness”divine assurance that God restores repentant sinners who accept the means of grace. From this we learn not to despair of our sins against others. The second is the promise of providence”divine assurance that, in the end, God will set everything to rights. From this we learn not to despair of the sins of others against us. Only because of these two promises can conscience serve as a guide and not as a rock to crush us.

Without the promise of forgiveness, natural law would show us only a face of accusation. Few could bear to look at it at all; none could bear to look at it steadily. Without the promise of providence, contemplation of the wrongs of the world would drive us to yet greater wrongs. Whether by its own guilt or by rage at the guilt of all others, the intellect would be undermined, and the counsels of natural law would be pulled in perverse directions.

These promises are more than affirmations about the nature of the world. They affirm a different class of truths, illuminating the intellect in a distinctive manner. Ordinary affirmations”that man is made in God’s image, that spouses join as one flesh, that divorce betrays posterity”draw the attention of natural reason to realities it might otherwise have slighted or overlooked. Promises instead inform natural reason of something it never could have known: the place of natural law in the economy of salvation.

Although both act on our mind, they do so in different ways. One adds to our data; the other one purges our will. Assured of God’s mercy, we no longer require the false comfort of thinking ourselves better than God. Assured of his providence, we are freed from the equally false need to play God with others. Cleansed of both kinds of despair, we can think more honestly about the natural law because we are no longer desperate or afraid. Hope turns out to be not only a spiritual but an intellectual virtue.


Finally we come to the fifth light”the light revelations sheds on nature through the sacraments . Even revelation about things above reason can give us clues about things that are not above reason.

Consider Paul’s explosive remarks about marriage in his letter to the Ephesians. From the outset, the language is daring. Wives are to submit to their husbands as to the Lord; husbands are also to submit, but in another and asymmetrical sense, loving their wives as Christ loved the Church and gave himself up for her. A turning point comes with Paul’s astonishing declaration that this is a “mystery” and that it is somehow “about” Christ and the Church.

Suddenly we see that his figures are more than analogies. He is saying that a natural reality and a supernatural reality not only happen to correspond but were made for this correspondence”that, in the depth of God’s creative plan, the marriage of the spouses invokes the Marriage of the Lamb and in some measure makes it present.

Paul calls this wonder a mysterion, something hidden and now revealed, but the Greek term is much more potent than its English cognate. It is the same word that the Greek Fathers used from the fourth century onward for the sacraments; the Douay-Rheims even translates it “sacrament.” It would be extravagant to read all the later developments of sacramental theology back into the text, but it is not extravagant to say that the grace Paul has in mind is the same kind we now call sacramental. He is claiming nothing less than this: Because of Christ, the natural event of marriage is not just a sign of a spiritual event but a participation in it”an event of such potency that a man and a woman are made really and permanently one, receiving the grace to be bound with the same love with which Christ and the Church are bound. Transmundane meaning and power are supernaturally transfused into vessels of flesh.

The possibility of such supernatural grace tells us something about natural reality. Though grace exceeds nature, it never violates it; nature could receive nothing from grace if it had not been fashioned ahead of time to receive it. This is certainly true of matrimony, for sacramental marriage builds on the covenantal and donational properties of natural marriage. Apart from the form of the covenant, the sacrament would be unintelligible; apart from the grace of the sacrament, the donation might seem almost impossible. Now among the laws of the intellect, one of the foremost is this: What we hardly fulfill, we can hardly discern. We can see the covenant better if we know the sacrament, too.

Supernatural grace, in other words, leaves a trace in nature. For an analogy, consider a dock. Merely by looking at a particular ship, we can see more clearly why the dock that holds it was designed in the way that it was. Afterward we can examine it to see if our inferences are borne out.

Nature is like that”the dock of grace, the place where the sacraments come to berth. And just the way the ship has left its signature on the design of the dock, so, if we know something about the sacrament, we can infer something about the natural institution that the sacrament ennobles. By knowing something about its grace, we can more easily perceive the shape of the pre-sacramental reality that is ordained to receive it. Afterward, natural reason can inquire to see if these inferences are true. And so, in an odd and indirect way, it turns out that the sacraments are a proper subject for natural law.

In the case of marriage, the sacramental illumination”the light on nature cast by divine revelation of the sacraments”clears up many things that would otherwise be obscure. There is a taste of longing for God even in natural marriage; somehow it participates in the sensus divinitatis. In almost all times and nations people have dimly perceived something of transcendent importance about it, and the ancient tendency to make idols of the potencies behind it is strong.

Strong, too, is our modern tendency to suppress the obscure longing for transcendence, which ends up treating marriage as less than it is. Nowhere outside of the truth of the sacrament can the supernatural end of natural marriage be understood. Nature is ordained the receptacle of grace: neither divine, nor simply profane, but a chalice.


Under the influence of the Enlightenment, natural-law thinkers scrubbed, little by little, whatever influence remained from the centuries of faith”whatever benefit they might have gained from the help of revelation. And, as a result, they lost the idea of nature, then the idea of law, and, finally, the idea of thinking. In the end, they found that they had scoured away the ground on which they were standing.

These five kinds of light that revelation shines on nature”the light of precept, of affirmation, of narrative, of promise, and of sacrament”suggest that philosophers should not be afraid of revelation. Although much of revelation concerns supernatural realities that the natural force of reason cannot confirm on its own, revelation also sheds light on natural realities”light that allows the intellect to see creation as it really is. Seeing, the intellect may show these realities to others.

This is what justifies our hope: That they really are there to be seen.

J. Budziszewski is professor of government and philosophy at the University of Texas at Austin and author of The Line Through the Heart: Natural Law as Fact, Theory, and Sign of Contradiction, forthcoming from ISI Press.