10.1 The Greek contributions to Natural Law Theory

We can trace the origins of this theory back to ancient Greece. Aristotle‘s influence on natural law ethics theory was profound and far-reaching. Although he didn’t explicitly formulate a theory of natural law as we understand it today, his ideas laid crucial groundwork for later thinkers. Aristotle introduced the concept of telos (end or purpose) in nature. He argued that everything in nature has an inherent purpose or function. Just as human artifacts are made for a purpose (e.g.: a knife is made to cut things; a clock is made to tell time) so too natural things have a purpose. For example, the purpose of a nut is to grow into a tree, the purpose of rain is to fall to the earth, the purpose of a heart is to pump blood through the body.

This teleological view became a cornerstone of natural law theory, suggesting that moral goodness involves fulfilling one’s natural purpose. Aristotle’s emphasis on virtue as central to ethics influenced natural law thinkers. He proposed that living a good life meant cultivating virtues that are in accordance with human nature. This idea of aligning behavior with nature became central to natural law ethics.

When it comes to us, Aristotle held that the purpose or telos of human life is eudaimonia (flourishing or well-being). In his Nichomachean Ethics he states: “For just as for a flute-player, a sculptor, or any artist, and, in general, for all things that have a function or activity, the good and the ‘well’ is thought to reside in the function, so would it seem to be for man, if he has a function.” (Book I, 1097b25-28) Moreover, the proper activity and highest functioning of human beings is their use of reason. “The function of man is an activity of soul which follows or implies reason.” (Book I, 1098a7-8) It is when we are using our reason to pursue a life of virtue that we are truly engaged in eudaimonia.

Now we state the function of man to be a certain kind of life, and this to be an activity or actions of the soul implying a rational principle, and the function of a good man to be the good and noble performance of these, and if any action is well performed when it is performed in accordance with the appropriate excellence: if this is the case, human good turns out to be activity of soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete. (Book I, 1098a13-18)

We shall return to Aristotle’s moral theory in our next chapter. For now, it is important to realize that his notion of a proper telos in nature and in human nature sets the foundation for Natural Law Ethics.

This foundation was advanced by a group of Greek and Roman philosophers known as the Stoics. Building upon and expanding earlier Greek philosophical ideas, the Stoics introduced the concept of a universal, Logos (divine reason) that permeates and governs the cosmos. They argued that this rational principle is the source of natural law, accessible to all rational beings. Stoics advanced the idea of a universal human community based on shared reason. This concept of world citizenship (cosmopolitanism) implied that natural law applies equally to all humans, regardless of their particular society or culture. While Aristotle emphasized human reason, the Stoics went further, arguing that our capacity for reason directly connects us to the divine Logos and natural law. As the Roman philosopher Cicero, influenced by Stoicism, wrote in De Legibus:

True law is right reason in agreement with nature; it is of universal application, unchanging and everlasting… And there will not be different laws at Rome and at Athens, or different laws now and in the future, but one eternal and unchangeable law will be valid for all nations and all times.

Because they held this inner law to be universal, the Stoics made significant contributions to the philosophical foundations that later developed into the theory of natural rights. While they didn’t explicitly formulate a theory of natural rights as we understand it today, their ideas laid crucial groundwork.

Natural Law Theory: Crash Course Philosophy #34 (9:39)

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