As a Christian schoolteacher, I have sometimes encountered a sort of conservatism that wants to refrain from appealing to the Bible in our nation’s legislation. God’s Word should not be allowed to direct and shape our leaders’ deliberations; rather, the process should be informed only by natural law, which is accessible to all men regardless of their faith in God, since all men are endowed with reason. On this basis, it is urged, we can avail ourselves of the wisdom of pagan wise men of the past — of the constitution of the ancient Roman republic, so much admired by the founding fathers (“Publius”, “Brutus”, “the society of the Cincinnati”, etc.), while refraining from the strife into which Christian claims seem to precipitate men.
I don’t think this works, however. I am convinced that there are both positive and negative reasons to resist the project of founding our politics and public discourse on natural law rather than on an express acknowledgment of Jesus’ sovereignty, exercised through the Scripture.
It is important to distinguish between “natural law” in the sense that many modern conservatives want to use it, and natural revelation. Truths about God are indeed manifested in the creation, but as John Calvin puts it in Institutes 1.5,
In vain does Creation exhibit so many bright lamps lighted up to show forth the glory of its Author. Though they beam upon us from every quarter, they are altogether insufficient of themselves to lead us into the right path. Some sparks, undoubtedly, they do throw out; but these are quenched before they can give forth a brighter effulgence. Wherefore, the apostle, in the very place where he says that the worlds are images of invisible things, adds that it is by faith we understand that they were framed by the word of God, (Heb. 11: 3;) thereby intimating that the invisible Godhead is indeed represented by such displays, but that we have no eyes to perceive it until they are enlightened through faith by internal revelation from God. When Paul says that that which may be known of God is manifested by the creation of the world, he does not mean such a manifestation as may be comprehended by the wit of man, (Rom. 1: 19;) on the contrary, he shows that it has no further effect than to render us inexcusable, (Acts 17: 27.)
According to Calvin, natural revelation is so obscured and twisted by the sin of every man that, far from acting as a practical and perspicuous shared foundation for public discourse, it is unable to do anything but render us without excuse.
As Peter Leithart puts it in his article “Natural Law: a Reformed Critique”, the only way natural law could provide us with any substantial norms for our own politics and ethics would be if the human reasoning by which it is received and applied “substantially reflects divine reasoning” — in other words, natural law can only guide us if we can perceive it correctly, and the obvious differences in moral and political reasoning among men make it impossible to believe that we do perceive it correctly.
In practice, it is often comical to watch appeals to nature in action: “Homosexuality in nature? Norway rats commit infanticide. Is that an endorsement for the practice in humans?”
More importantly, the Bible does not teach natural law. Markus Bockmuehl has this to say on the topic:
In the past, scholars frequently considered Romans 2.14-15 to be the key New Testament passage on natural law. Paul seems here at first sight to allow for the possibility of a ‘natural’ law observance by Gentiles. Upon closer examination, however, the passage turns out to have remarkably little to say about [natural law]. At best, it allows for the possibility that some Gentiles might ‘naturally’ (phusei) keep the requirements of the Torah. What is in view is the possibility that some of the Torah’s stipulations (ta tou nomou) might be kept instinctively by Gentiles who do not actually know them. Paul’s concern, in other words, is not some sort of separate ‘natural law’, but rather a ‘natural’ or common-sense knowledge of the one Law of God, subjectively mediated by the individual’s moral consciousness. (Jewish Law in Gentile Churches, p. 129)
But are there positive reasons to reject natural law? I believe there are. The New Testament presents a consistent claim that Jesus’ supremacy is to be proclaimed in every area of human life; there is, in Kuyper’s phrase, “not even an inch” over which Jesus does not cry, “Mine!” Far from preserving politics as a neutral sphere, or handing it over to the domination of Satan, Jesus insists on being acknowledged by the rulers of this world: every knee shall bow, and every tongue confess that He is Lord. When Paul is confronted by Felix, he does not hesitate to reason with him about “righteousness, self-control, and the judgment to come.” Felix “was afraid.” (Acts 24)
Not for nothing is Psalm 2 the most-quoted Psalm in the New Testament: “Now, therefore, be wise O kings; be instructed, you judges of the earth! Serve the Lord with fear, and rejoice with trembling; kiss the Son, lest He be angry, and you perish in the way, when His wrath is kindled but a little. Blessed are all they who put their trust in Him.” Kissing the Son is, at the least, a formal acknowledgment of His authority and supremacy. To say that we may have a polity without acknowledging Him, is to invite His wrath.
This means that we must reject any political deliberation to frame a commonwealth as though its prosperity, success, and righteousness were a mere matter of getting the structure correct, and had nothing to do with Jesus Christ — as though the establishment of a wise and righteous society were simply a matter of using our Reason to attend to the accumulated goodness of the Western Tradition, with no need to trust in the Lord or name Him in our public life.
The Bible, by contrast, speaks consistently as though this were the main thing that matters — because the prosperity, success, and longevity of a nation are really from the Lord, and are not the products of human ingenuity and chance.
Therefore the classical liberal project of establishing a polity on the law of nature is simply doomed. Because it does not confess Christ, it is building on sand, and will come to nought.