This paper examines the concept of natural law from its medieval roots through the seventeenth century, tracing the contributions of Thomas Aquinas, Thomas Hobbes, and John Locke. It distinguishes natural law from the laws of nature, explores Aquinas's divine-rational framework, Hobbes's mechanistic view of human nature, and Locke's emphasis on self-preservation and natural rights. The paper then addresses key objections to natural law theory — including critiques based on historical relativism, ontological and epistemological concerns, political utilitarianism, and the absence of scientific verification — while noting the internal distinction between natural law as moral theory and as legal theory, and the concept of the Overlap Thesis.
The paper demonstrates the technique of comparative intellectual history: it places three canonical thinkers in dialogue with one another, identifying both continuities (e.g., self-preservation as a shared concern for Hobbes and Locke) and divergences (e.g., Aquinas's theological grounding versus Hobbes's mechanistic materialism). This approach shows how a single concept evolves across different philosophical contexts.
The paper opens with a conceptual clarification, distinguishing natural law from the laws of nature. It then proceeds chronologically through Aquinas, Hobbes, and Locke before stepping back to analyze the internal structure of natural law theory (moral vs. legal theory; the Overlap Thesis). The final section surveys objections, including those from Leo Strauss, L.A. Rollins, and Marxist historical materialism, before briefly noting the advocates' response. The conclusion is embedded within the objections section rather than standing alone.
What constitutes religion, science, sociology, and so on is hard to define and ambiguous at times. Take, for instance, fundamentalism in religion, the fact that life is still difficult to define in scientific terms, or the complexity of natural law — in Latin, lex naturalis. What each of these three issues has in common is the difficulty they impose on someone trying to get to the bottom of them, because there are so many perspectives from which one could approach them and none is self-sufficient.
In the seventeenth century, two key concepts started to gain power over scholars. These concepts originated in the medieval period but had not stretched far enough to gain universal dominance until then. The first is the laws of nature, something natural philosophy was concerned with, and the second is natural law, a term frequently used in jurisprudence and political theory. To be more specific, consider science: what applies as a law of nature is, for example, Newton's law of gravitation, meaning that gravity is something true and valid anywhere in the world, everywhere in the universe. Thus, a law of nature requires foolproof certainty. If we hold an apple in our hand and then let it go, the apple will fall — it is something we know, and we acknowledge that it is within the apple's "nature" to fall to the ground. Hydrogen atoms combined with oxygen will result in water molecules, which is something "naturally" specific to hydrogen, oxygen, and water. There is nothing ambiguous about these observations, as Murray Rothbard has pointed out (9).
What, then, makes natural law such a controversy? The term is often used to refer to theories of ethics, politics, and civil law, as well as religious morality. But unlike in the case of the laws of nature, there is only a quantum of certainty — sometimes none at all — that can be ascribed to natural law.
Because it was noted that both concepts — the laws of nature and natural law — were somewhat common ever since the Middle Ages, it is fitting to start there when considering the development of natural law. As a starting point, the theory of Thomas Aquinas, a central figure in the natural law tradition, is particularly valuable. What Aquinas did was to base his doctrine on natural law as perceived by him in relation to God and His creation. He encompassed within his doctrine two perspectives: one regarding God as the giver of the natural law, and the other yielding man's participation as the receiver of the natural law. That is to say, God — as the main principle and reason for things — unites people around Him by setting two distinct but subsidiary paths: He helps humanity by offering Divine Grace while also advising people on the law. For Aquinas, the two were a perfect blend, because following the law came not as the result of coercion but rather as the fulfillment of one's very nature.
This double perception of reality — grace and nature — led Aquinas to the conclusion that nature is fulfilled supernaturally. In other words, people are motivated by the enlightenment of the divine plan when enacting the law, and the law is not merely perceived as a set of regulations and restrictions, but as a positive means for people to reach happiness. Thomas Aquinas's view of natural law, based on a rational-divine theory, is actually a continuation of Aristotle's natural law. By intuiting that the principles of nature lay at the foundation of moral authority, the natural law tradition adopted the idea that nature can serve as a role model for humanity.
The natural law moral theory, as perceived by Aquinas, is therefore the gift of consciousness to man through the "enlightenment" placed within us by God. At the same time, through man's expression of the original moral sense, natural law advises people in regard to human conduct so that rational order and the common good are assured. Man's rights and duties thus lead to responsibility and personal dignity. This is how people take part in God's work and participate in the divine: through the intermediary of natural law seeded within humanity by God Himself. In summary, from Aquinas's point of view, natural law was connected to divinity and was part of God's rational plan for humanity; man is thus a participant in the law but possesses the reason and free will to act upon it as he wishes. Aquinas's views were absorbed and further developed by many scholars throughout time, with modernists on natural law having been highly inspired by Thomistic Natural Law, and some of the most modern philosophies having been at least partly influenced by it.
Another central figure regarding the concept of natural law who shared some common ground with Aquinas is Thomas Hobbes, an English philosopher born in the sixteenth century. Hobbes witnessed some of Europe's religious crises at a time when the English Revolution led many people to face a loss of religious identity, especially given an ancient opposition to the influence of the church regarding taxes imposed by the papacy and its involvement in political affairs. There were those who supported the monarchy as something derived from a social context — from the people's will, Hobbes among them — and others who considered that monarchy was of divine origin. Public debates were constantly ongoing about ethical, political, and social issues. It was around this time that Hobbes introduced his work, Leviathan, which encompassed the idea that the world is mechanical and that nature itself follows the same principles that govern the functioning of an organism, such as the body of an animal. It was his opinion that, since God had created nature like a mechanism, He must have done the same in regard to human beings. Similarly, man had created the state, or Commonwealth, to ensure protection.
Built according to the very laws that governed nature, man, as Hobbes saw it, was an assembly of mechanisms functioning according to cause and interaction with others. The body was represented as a machine "driven" solely by the mind, with emotions and feelings resulting only as effects of chemical processes. The idea that everything was therefore rational calculation — with no spontaneity — later inspired Kant in his construction of the moral man. Hobbes believed that people's nature aspired toward the terrestrial and therefore the material, and that because of this, all evil emerged. His vision of natural law thus shifted from morals toward the idea of man's self-preservation.
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