Those RULES of old discover’d, not devis’d,
Are Nature still, but Nature methodis’d;
Nature, like liberty, is but restrain’d
By the same laws which first herself ordain’d.

– Pope, An Essay on Criticism (writing here of aesthetic laws)

… the Laws of Nature and of Nature’s God  …

— The Declaration of Independence

How does one determine whether a law is just or unjust? A just law is a man made code that squares with the moral law or the law of God. An unjust law is a code that is out of harmony with the moral law. To put it in the terms of St. Thomas Aquinas: An unjust law is a human law that is not rooted in eternal law and natural law. Any law that uplifts human personality is just. Any law that degrades human personality is unjust. All segregation statutes are unjust because segregation distorts the soul and damages the personality. It gives the segregator a false sense of superiority and the segregated a false sense of inferiority.

— Martin Luther King, Jr., Letter from Birmingham Jail

As I begin to teach a course on Martin Luther King–and while thinking about how to teach civics at all levels–I am giving renewed consideration to the idea of natural law. This is a matter for debate (and should be presented as such), but here are some personal thoughts:

A substantial part of any concept of natural law is a set of rights. Rights impose obligations. If I have a right to life, you have an obligation not to kill me. If I have a right to an education, someone has an obligation to pay for my schooling. These obligations fall on both individuals and institutions. For instance, my right to life implies not only that you may not kill me but that some kind of state must protect me.

To honor and protect others’ rights is obligatory. It is a moral and not merely a legal duty.

Governments do not create rights and obligations, because we can and must assess any given government by asking whether it protects the rights that people deserve.

Other animals have rights because people have obligations to treat them ethically. But non-human animals do not have rights in relation to each other. In that sense, rights are human, although they extend to humans’ treatment of other species.

Rights are linked to the organism’s characteristics as a natural species. For instance, we human beings are born helpless, remain interdependent, yet develop unique goals and desires that are rooted in our private mental lives. Our rights would be different if we had no need for each other, or no private lives at all–or if we differed in other fundamental ways from actual homo sapiens.

Rights are connected to happiness, which means–not the balance of pleasure over pain–but some deeper form of flourishing or self-realization. Flourishing for human beings is natural in the same way that a mouse or an apple tree has certain natural ways of flourishing.

At the same time, one of the unusual and fundamental features of human beings is our ability to flourish in many different ways, and so we have a right to choose our own paths or be the authors of our own lives. This right to choose is based on our ability and desire to choose, which is a natural characteristic.

I have suggested that fundamental interests, needs, and goods are rooted in nature. However, it is not a natural principle that anyone has an obligation to protect or provide for the needs of anyone else. An individual rabbit has a profound interest in not being eaten, yet a fox does not have an obligation to refrain from eating rabbits. Nature is red in tooth and claw.

We are obligated to honor everyone else’s rights, which are based in their natural interests, but this obligation is not natural. It comes from somewhere else. If you think it comes from God, that is fine, but the obligation is then divine and supra-natural, not (merely) natural.

Perhaps we have an instinct to universal beneficence that emerges from our everyday sympathy for other people and animals. That instinct could be seen as the natural (not divine) basis for our commitment to universal rights. Mengzi puts it very well:

Humans all have hearts that are not unfeeling toward others. Suppose someone suddenly saw a child about to fall into a well: everyone in such a situation would have a feeling of alarm and compassion—not because one sought to get in good with the child’s parents, not because one wanted fame among their neighbors and friends, and not because one would dislike the sounds of the child’s cries. [F]?rom this we can see that if one is without the heart of compassion, one is not a human. If one is without the heart of deference, one is not a human. The heart of compassion is the sprout of benevolence. The heart of disdain (shame/disgust) is the sprout of righteousness. The heart of deference is the sprout of propriety. The heart of approval and disapproval is the sprout of wisdom.” (2A6; see also 6A6)

Quoted in Owen Flanagan, The Geography of Morals (p. 57). Oxford University Press. Kindle Edition.

However, we have many instincts, including warlike, competitive, and cruel ones. Universal beneficence seems a subtle and rare sprout in the wild garden of our instincts. To select and cultivate that particular sprout may be wise and right, but it is a choice that’s not itself directed by nature.

Nature can be understood as everything that science can explain (and science is any valid explanation of nature). So defined, “nature” offers no basis for obligations. A purely empirical study of nature would suggest that members of any species, including homo sapiens, are unequal in capacity, frequently selfish, and fully determined by physical processes rather than choice. We can broaden our understanding of nature to encompass things like obligations, purposes, and goods–for instance, happiness as the purpose of human beings, and non-domination is a good required for happiness. But then nature is not exhausted by positivist science.

Partly because positivist science does not comprehend things like rights, it is very hard for people to know the ideal list of rights and their correlative obligations. All of our ancestors were wrong about some rights–according to us–which means that we ought to be humble about our own ability to know the ideal list.

The best we can do is to decide, in reasonably fair and reflective forums, which rights and obligations ought to apply to whom. That means that although governments do not create rights, people must identify and determine rights through politics and in institutions such as governments. We should expect their outcomes to vary over time and space, not because rights are mere matters of opinion, but because the only way we can know real rights is to exchange and test our opinions.

In conclusion, I feel comfortable speaking of law that is importantly connected to nature, and especially to the nature of human beings. Understanding it requires reflection on our natural circumstances. But I wouldn’t call it “natural law” if that implies that it is part of, or determined by, nature, because it has sources other than nature itself.

See also: is science republican (with a little r)?; science, law, and microagressions; my self, your self, ourselves; the moral significance of instinct, with special reference to having a dog; is everyone religious?; is all truth scientific truth?; latest thoughts on animal rights and welfare; and Korsgaard on animals and ethics.