Before there was a law under the American Constitution, there was an argument about the law. It was an argument, that is, about the ends of the law, and the framework of a lawful government. This was, of course, the argument over the Constitution, and it seems remarkably to have escaped recognition these days that an argument of this kind is itself a dramatic illustration of “natural law.”...
As John Locke pointed out, the legislature would be the source of the “positive law,” the law that was enacted or posited. But what, he asked, would be the source of the legislature? From what would that spring?...
...The law in England, made familiar by William Blackstone in his Commentaries, began with the notion of a sovereign issuing commands. But the law in America, said Wilson, would begin “with another principle, very different in its nature and operations”: “Laws derived from the pure source of equality and justice must be founded on the consent of those, whose obedience they require. The sovereign, when traced to his source, must be found in the man.”
The appeal then had to be to those first principles “antecedent to all positive law,” an appeal to “nature”—or, as Aristotle would say, to an understanding of that creature who was by nature suited to political life....
In ... Chisholm v. Georgia, James Wilson ... found it necessary to speak about “the principles of general jurisprudence” and to acknowledge the laws of reason and “the philosophy of mind.” And so, before Wilson invoked the authority of any case at law or any commentator on matters jural, he invoked the authority of “Dr. [Thomas] Reid, in his excellent inquiry into the human mind, on the principles of common sense, speaking of the skeptical and illiberal philosophy, which under bold, but false pretensions to liberality, prevailed in many parts of Europe before he wrote.” Wilson began, then, by rejecting skepticism as the fount of all forms of relativism in morality and law.
As a contrast ...in Planned Parenthood v. Casey in 1992 ... Justices Sandra Day O’Connor, Anthony Kennedy, and David Souter wrote a plurality opinion in which they enjoined the country to cease its agitation over this issue. In restating the claim for a right to abortion, the three judges sought to soar to a level poetic, and delivered themselves of this profundity: “at the heart of liberty is the right to define one’s own concept of existence, of meaning, of the universe, and of the mystery of human life.” The founders began by rejecting skepticism and relativism in philosophy and morality; the modern judges—products of the best law schools in the land—affirm the right of a person to make up his own version of the universe.