Stoics Conceptualize Natural Law

By positing a universal moral law independent of cultures and religions, the Stoics established the foundations of modern conceptions of human rights and law based on human reason.

Summary of Event

The formulation of the Stoic concept of natural law was the logical culmination of trends in cosmological thought and political development in the Greek world after the time of Hesiod (fl. c. 700 b.c.e.). Implicit in Hesiod’s Theogony (c. 700 b.c.e.; English translation, 1728) is an understanding of the world order as political in nature and of physical nature as obedient to the orderly processes of thought in the human mind. Early Ionian philosophy, especially that of Anaximander (610-546/545 b.c.e.), had given explicit formulation to these implications of Hesiod’s poem in the concepts of a cosmic justice governing all natural phenomena; the logos of Heraclitus of Ephesus (c. 540-c. 480 b.c.e.) expressed an active rational principle permeating all nature and directing its phenomena. Zeno of Citium

Although these cosmological ideas were themselves derived from the political framework of the polis (city-state), there seems to have been no reapplication of them to the political and moral relationships of persons within different political and ethnic communities of the world until the mid-fifth century b.c.e. At that time, the Sophists called attention to the relativity of current moral and political standards, or nomos, in different communities and then pointed to a common human nature, or physis, with laws of its own that might well conflict with laws of human communities.

As the institutions of the Greek polis were losing their power to command the loyalties of individuals, the Athenian Socrates (c. 470-399 b.c.e.) postulated an objective and rational standard of moral human behavior based on the nature of the individual man as a rational and social being. Plato (c. 427-347 b.c.e.) further developed this conception of a rational human nature and a rational moral law in the Politeia (388-369 b.c.e.; Republic, 1701) and the Nomoi (360-347 b.c.e.; Laws, 1804). Philosophy of the fourth century b.c.e. failed to realize the universalist implications of these ideas, probably because the polis remained the only obviously self-validating type of human community; but the conquests of Alexander demolished such claims for the polis and created in fact a universal human cultural community throughout the civilized areas of the eastern Mediterranean world. Koine Greek became a common language of international commerce and culture, and through this medium the cultural heritages of Greeks and “barbarians” cross-fertilized each other.

The earliest explicit recognition of the community of humankind seems to have been more a negative statement of the individual’s rejection of ties to the local community than a positive affirmation of human brotherhood. The Cynic Diogenes (c. 412/403-c. 324/321 b.c.e.) is said to have been the first to call himself a “citizen of the world” by way of denying any personal obligation to the polis. Far from being a political idealist, Diogenes held that all humans and beasts are related inasmuch as humans are beasts. All culture is artificial; a person keenly aware of what nature requires will find contentment without heeding the conventions of the community in which the person happens to reside.

The Stoic school of philosophy was established by Zeno of Citium about 300 b.c.e. and received its name from Zeno’s practice of teaching from the porch (stoa) at the Athenian market. It was more fully developed and disseminated by Zeno’s successors, Cleanthes and Chrysippus. Stoicism was the dominant philosophy of educated persons in the Hellenic world for five hundred years until it was replaced by Christian thought, which incorporated many of its tenets, especially that of natural law. Stoicism has three main periods referred to as Old Stoicism, Middle Stoicism, and Roman Stoicism. It is the first and last periods which are important to the conception of natural law.

The basis for natural law theory developed in Old Stoicism and was given its practical application in the form of Roman law and governance during the period of Roman Stoicism. Stoicism developed out of Cynicism and evolved more systematically the Cynic school’s conception of “the life according to nature.” While the Cynics, however, had set a low estimate on a person’s rational capacity, the Stoic conception of persons and their place in nature laid a supreme value on this rational capacity. Taking the cosmology of Heraclitus as a physical foundation for his system, Zeno postulated a cosmic monism of a pantheistic nature in which logos, or “active reason,” pervades all nature and determines all events and also provides a moral law. God is present in all nature, yet God, or logos, has consciousness only in the souls of persons and in the totality of the universe. Since God and persons as conscious participants in the events of nature and of history are thus distinguished from plants, animals, and inorganic nature, God and all persons are bound together in a natural community of all rational beings.

The Stoic ethic comprises two complementary levels of the rational life according to nature. One is the inner level of assent by the logos within to the pattern of events determined by the universal logos, a recognition of the necessity and rationality of all that does in fact occur, contentment with fate, or in Stoic diction apatheia, imperturbability. Yet on the external level of practical moral response to critical choices confronting the individual, reason guides choice to fulfillment of duty. Duty is that portion of the responsibility for fulfilling the rational operation of nature and history that confronts the individual moral agent. Duty is not limited by geographic, ethnic, political, or even social boundaries. It is laid on the individual not by the state or ancestral mores but by the rational principle that governs the universe, and therefore it extends to all human beings who, since they are endowed with reason, are members of the world community, the cosmopolis.

Seneca the Younger.

(Library of Congress)

Although the early Stoic concepts of cosmopolis and natural law defining the duties of all rational beings are stated in positive form, in the period of the Old Stoa these ideals are essentially nonpolitical; they do not lead to any positive vision of the political unity of humankind. Citizenship is not a person’s highest obligation, and while it is asserted that the laws of a state ought to reflect the natural laws and ought to be disobeyed if they contradict them, Stoic idealism in the early period could not envision a universal state over which a single code of law reigned supreme. With the emergence of the Roman Empire, however, Roman rulers were confronted with the very practical problem of finding a universal law and morality that was to govern persons of diverse cultural and religious backgrounds. It was during this period that Roman philosophers, especially Cicero, Seneca the Younger, Epictetus, and Marcus Aurelius, more fully developed the practical aspects of natural law theory to provide a foundation for political, civil law based on universal moral principles. These universal principles were understood to be accessible to all persons by virtue of their participation in universal reason (the logos).


Stoicism was so influential that Seneca served as the tutor of the emperor Nero, and Marcus Aurelius was himself emperor of Rome. The concepts of cosmopolis and natural law were thus ultimately influential in the formulation of the Roman imperial ius gentium (universal applied law). Stoic moral thought, especially the concept of natural law, was also very influential in the systematic formulation of the moral philosophy of the Christian Church, and it received formal development in the work of the medieval theologian Saint Thomas Aquinas (1224 or 1225-1274 c.e.). The entire conception of natural law became a basis for modern theories of the equality of all persons since all participate in universal reason. It also provides the primary source for modern conceptions of human rights and international law.

Further Reading

  • Inwood, Brad, ed. The Cambridge Companion to the Stoics. New York: Cambridge University Press, 2003. A collection of fifteen essays on all aspects of Stoic philosophy. A valuable introduction.
  • Long, A. A. Hellenistic Philosophy: Stoics, Epicureans, Sceptics. 2d ed. Berkeley: University of California Press, 1986. Locates Stoicism in the context of Hellenistic philosophy and the cross influences of the various traditions.
  • Schofield, Malcolm. The Stoic Idea of the City. Reprint. Chicago: University of Chicago Press, 1999. A discussion of the Stoic ideas of political order.
  • Verbeke, Gerard. The Presence of Stoicism in Medieval Thought. Washington, D.C.: Catholic University of America Press, 1983. A discussion of Stoicism’s influence on Christian thought and its role in shaping Western conceptions of ethics and natural law.
  • Weinreb, Lloyd. Natural Law and Justice. Cambridge, Mass.: Harvard University Press, 1987. A general discussion of natural law.

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