Natural Law, Eighteenth-Century Understanding

The concept of natural law describes universal laws that exist independent of human-created laws. It is a highly contested idea both in philosophy and legal theory. Natural law as it influenced early American thinking on civil liberties was largely the product of the European Enlightenment as it was received and reinterpreted by the founders.

The study of natural law had been dominated by Catholic scholasticism for centuries. Expressed in the thinking of theologians such as Thomas Aquinas, natural law was analyzed in terms of God-given laws, and what that meant for human institutions. The Enlightenment forced the study of natural law towards secular rationality and individualism, with a new attention to political rights, and no Enlightenment philosopher influenced the American colonists more than John Locke.

Locke created a wealth of new natural rights ideas, imagining a ‘‘state of nature’’ that predated government, and describing the natural rights that arose therein. Locke’s theories also envisioned government as a social compact requiring the ‘‘consent of the governed.’’ Locke’s theory of the ‘‘consent of the governed’’ strongly influenced the intellectual forbears of the nascent republic, who oftentimes deployed Lockean natural rights rhetoric when arguing for the dissolution of ties with Britain. The Declaration of Independence provides a good example of this kind of reasoning, such as where it expresses that the British have deprived the colonists of ‘‘the separate and equal station to which the Laws of Nature and of Nature’s God entitle them.’’

Natural Law and the Constitution

There is debate, however, among historians of the early American republic about the extent to which natural law influenced the drafters of the Constitution. As mentioned above, the Declaration of Independence certainly included natural law language, but the Constitution eschewed such rhetoric for much more formal legalistic terms, and natural law is not mentioned in any significance in the ratifying debates. One explanation, proffered by John Hart Ely, is that the functions of the documents were fundamentally different. The Declaration was an announcement of grievances, and an argument that those grievances could only be redressed by resort to revolution. By contrast, the Constitution, drafted after long debate and deliberation, was meant to be the written fundamental law of the new nation. We might conclude that while many of the framers of the early republic valued natural law individually, they thought that humanwritten laws were the only sources of state-enforced obligations.

One important concept for civil liberties that permeates natural law theory is the idea that positive, human-written laws do not exhaust the limits of individual rights against government. This means that there are universal, individual rights that cannot be violated by government. This insight is important to understanding the continuing vitality of natural law theories for protecting civil liberties in the modern United States. Some of these modern theories suppose that if there are preexisting natural rights, then these natural rights form an ‘‘unwritten constitution’’ that underlies the written constitution, but has as much or more force as the document itself.

There is a conflict between this view and the view that whatever natural rights there are, they are adequately protected by a written constitution. This struggle is evident in the debate over the inclusion or exclusion of a bill of rights. Those who would have excluded the Bill of Rights were not foes of individual liberties, but in fact thought those liberties would be best protected without a bill of rights. Alexander Hamilton, in The Federalist 84, gave expression to this very idea when he spoke of the danger of attempting to list all individual rights against government— an effort he thought impossible. Ultimately, those in favor of listing individual rights against government prevailed, and natural law was not significantly invoked by the judiciary in its interpretations of the Bill of Rights.

Natural Rights

However, this debate was not fully resolved by the framers of the Constitution, as evinced by the existence of the Ninth Amendment. That amendment states simply, ‘‘The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.’’ If we think that the fundamental law of the land is stated by the Constitution, then where would these rights ‘‘retained by the people’’ come from? Furthermore, should the vague provisions of the Fourteenth Amendment give rise to broad judicial protection of rights not listed in the Constitution? To some scholars, natural law answers these questions in the affirmative.

Such a theory has been embraced by some modern constitutional scholars, but in the framing period, appeals to natural law found only rare and fleeting traction in the U.S. Supreme Court, and the Ninth Amendment itself has been very rarely invoked. The 1798 case of Calder v. Bull (1798) is famous for juxtaposing the views of Justices Chase and Iredell, who come to opposite conclusions regarding the merits of using natural law as a source of constitutional law, with Chase in favor and Iredell opposed. That Justice Iredell prevailed in that case is testament to the strong tradition of legal positivism on the Supreme Court, which is marked by the belief that only the written Constitution is enforceable.

This view was dominant until the twentieth century (with a few exceptions), when a quasi-natural law conception of the Constitution was revived, principally by late twentieth-century legal academics. The only justification for enforcing the ‘‘unenumerated rights’’ created by the Warren and Burger Courts seemed to be a revival of natural law. Whether this is a valid source of constitutional law continues to be a lively and intense debate both within and outside of the legal academy. Fundamentally, however, this debate is the culmination of long-unsettled questions about whether the fundamental law of the United States is exhausted by the text of the Constitution, or whether the text and history of its drafting invite judges to protect rights not written in the Constitution, and guaranteed by natural law.


References and Further Reading

  • Bailyn, Bernard. The Ideological Origins of the American Revolution. Cambridge, MA: Harvard University Press, 1967.
  • Ely, John Hart. Democracy and Distrust: A Theory of Judicial Review. Cambridge, MA: Harvard University Press, 1980.
  • Rossiter, C., ed. The Federalist Papers. New York: Penguin Putnam, 1961.
  • Wood, Gordon S. The Creation of the American Republic 1776–1787. Chapel Hill: University of North Carolina Press, 1969.

Cases and Statutes Cited

See also Calder v. Bull, 3 U.S. 386 (1798); Constitution of 1787; Declaration of Independence; Locke, John; Ninth Amendment; Roe v. Wade, 410 U.S. 113 (1973); Substantive Due Process; Warren Court


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