At times, the dialogue between my friend Hadley Arkes and the constitutional originalists he most admires—eminent jurists such as Robert Bork and Antonin Scalia—seems less like a difference of opinion than a case of ships passing in the night. What it needs is for someone to drop an anchor. This is what Professor Arkes undertakes to do in Constitutional Illusions and Anchoring Truths, the latest of his several books, and one that brings to bear his full arsenal of erudition, piercing insight, razor wit, and good cheer.

Arkes is the Edward Ney Professor of American Institutions and Jurisprudence at Amherst College. His passion is that first of first things, the natural law. In a manner of speaking—a very fundamental manner—this makes Arkes a constitutional originalist because, as he powerfully demonstrates, the American Framers were steeped in natural law. Never did they lose sight of the fact that, to paraphrase Chief Justice John Marshall’s often invoked (and often abused) maxim, it was a Constitution they were sculpting.

The injunctions crafted by the Framers were not to be exacting regulations prescribing minimum wages, maximum labor hours, or a robust system of wealth transfers flying under the beguiling flag of “entitlements.” They were, instead, the foundation for the continued flourishing of a pre-existing free society. Their purpose was to secure liberty—without defining the manifold aspects of liberty—against the insatiable appetite of government to encroach. Arkes quotes Hamilton in Federalist 31: “In disquisitions of every kind, there are certain primary truths, or first principles, upon which all subsequent reasonings must depend.” The Constitution was designed to capture these first principles, containing “an internal evidence which, antecedent to all reflection or combination, command the assent of the mind.”

If the Constitution was to endure, only anchoring truths, the truths of natural law, would fill the bill. Importantly, these were not (as is often supposed) truths about the laws of nature that govern all things and beings—what, Arkes quips, may be called “the Kern and Hammerstein theory of natural law: ‘fish gotta swim/birds gotta fly.’” Natural law was not to be confused with “regularities in nature, or with generalizations about the behavior of humans over time, drawn from the checkered history of our species”—a history in which, for example, infanticide and genocide crop up with disturbing regularity. To the contrary, natural law presumes things that are higher and lower in human nature. Human reason, with the singular power to discern right and wrong, strives to elevate what Lincoln appealed to as “the better angels of our nature.” A system founded on natural law promotes justice even if it is not so haughty as to believe it can identify, or posit, each instantiation of justice past, present and future—or even that it should posit easily knowable instances of justice. The Framers, Arkes explains, were leery of positive law. Owing, again, to their preoccupation with human nature and its imperfections, some of them feared that written law would undermine reverence for a society’s unwritten principles, customs, and traditions—effacing, in a free society, any liberties not reduced to writing.

The constitutional convention thus featured fierce debates on whether there should be a Bill of Rights at all. This, Arkes reminds us, was precisely because individual liberty was presumed. It was antecedent to the Constitution, yet the exercise of engraving select freedoms into the document would, over time, be mistaken to imply that they flowed from the document rather than from the first principles that informed the document. This would degrade the pedigree of countless freedoms left unwritten—a misimpression the Ninth Amendment was meant to correct, however ineffectually. James Wilson and Oliver Ellsworth even opposed the proposal (nevertheless adopted) that the Constitution bar ex post facto laws. So universally understood was the principle that one could not be retrospectively penalized by a law enacted after one had acted, they feared educated people would conclude that those who perceived the need to write it down must have constituted a government “ignorant of the first principles of Legislation.”

For Arkes, the faithful interpretation of our Constitution consequently cries out for resort to natural law. The Constitution is more thematic than detailed. It is in the interstices that real-life problems arise, and the answers to these problems lie in first principles. Moreover, where the Constitution does issue specific commands, it paints in broad strokes: “due process,” “equal protection,” “cruel and unusual punishments,” “unreasonable searches and seizures,” and so on. To construe these terms in contemporary situations, sometimes involving technologies unforeseen at the time of the Constitution’s adoption, it is essential to draw on the natural law principles that animated the Framers.

Arkes makes this point effectively in several particulars. Most notable is the aforementioned prohibition on ex post facto laws. The principle seems clear enough . . . or is it? Sure, a man may not be convicted for an act that had not been outlawed when he committed it. But newly legislated civil laws often have harsh collateral consequences. Were Congress to repeal, say, the tax deduction for mortgage interest, it would dramatically increase the cost of home ownership and deplete a home’s value as a salable asset. The courts, however, have narrowed the ex post facto proscription to criminal laws even though, as Arkes shows, penalties in the civil context can be every bit as punishing and every bit as violative of the underlying principle.

Such examples convincingly prove that first principles should guide our public debate over legislation, over the kind of society we should be and the degree to which individual liberty should be subordinated to the public good—indeed, over what the “public good” actually is. It is here, however, that the argument between Arkes and the originalists skids off the rails.

Arkes maintains that because our Constitution is rooted in natural law, so too must be the profession of judging. He pointedly rejects what he takes to be the originalist counter-claim that judges must be legal positivists. Originalist judges insist that their interpretive task is limited to a formal determination of whether the Constitution empowers a legislature to enact the statute in question; theirs is not to question whether, as a matter of policy, the substance of the act accords with natural law or is otherwise sensible. For Arkes, this is a capricious distinction. As he sees it, judges are “doing natural law” whether they admit it or not, for the Constitution frequently provides not so much an answer to modern problems as a path to their solution. The first principles are the path.

The most provocative chapter in this engaging book is Arkes’s attempt to rehabilitate Lochner v. New York (1905), which struck down labor law limitations on the hours bakery employees could work. The case is reviled on the left for its veneration of economic liberty. (It was eventually overrun by the New Deal.) But it is equally castigated by originalists—taken to be the political right—because the “liberty to contract” it purported to find in the Fourteenth Amendment is a sheer judicial invention.

And here is the rub. Originalism is not a philosophy of the right or the left. It is a philosophy of sovereignty. The first principle of the free society vouchsafed by the Constitution is that the people are sovereign. Pace Professor Arkes, the originalists are not saying that no one should do natural law, or even that judges should never resort to it. They are saying that natural law is the preserve of the democratic process—the people through their elected representatives. Judges must wrestle with first principles when called on to construe the original understanding of specific constitutional provisions. But to manufacture such theories as Lochner’s “substantive due process” in order to impose the judicial perception of first principles usurps the capacity of free people to govern themselves.

The line between judicial interpretation and imposition is murky. Wherever it is drawn, reverence for our first principles—in both the political and judicial spheres—is imperative if we are to preserve the society the Framers sought to perpetuate. In that endeavor, Hadley Arkes remains a beacon in the dark night.