A friend of mine asked me yesterday, "What gives a society the right to coerce [some] of its members?" He didn't ask this question rhetorically, he believes that sometimes society really does have the right to coerce its members, so he wants to know where these rights come from, and how we know what they are.
My friend has stated earlier that he's a moral objectivist and perhaps a realist: morals, values, ethical principles really do exist, independently of our opinions about them, and we can (somehow) know they are true. I, however, have a different view. I have written at some length on meta-ethical subjective relativism, where I hold that our moral beliefs are fundamentally related to our subjective natures.
From my subjective relativistic view, I see our use of language to discuss rights is confused and sometimes fundamentally in error, especially when we draw conclusions from linguistic habits. We talk about "rights" as if they were objects "out there" in the world, in the same sense that rocks and trees, or physical laws, are "out there." But they're not. Instead, "rights" refer to two different, but related, kinds of subjective facts. First, rights refer to explicit, socially constructed legal or customary standards of behavior. The First Amendment and its associated jurisprudence, for example, establish the legal right, and the limitations of that right, of free speech. But legal rights don't exist in a vacuum; we create the legal right to recognize certain facts about the minds of people, i.e. subjective facts. First, people want free speech, at least for themselves individually. Second, we have found from experience that when we legally protect speech, our society operates more smoothly, peaceably, and responsively.
Meta-ethical subjective relativism is a fundamentally pragmatic philosophy. It's not about what we should do whether we like it or not; it's about our preferences, what we actually do like. Of course, our preferences are not infinitely labile; we are products of our biological and cultural evolutionary history, and this history constrains our actual preferences, our available preferences, and how preferences change over time.
Similarly, the natural world constrains our preferences, both individually and socially. Given how things are today, some changes in one individuals' preferences cannot easily propagate to others, and eventually disappear. Other changes in preferences result in social collapse in cultural "group selection" events, such as revolutions, conquests, military defeats, again causing those preferences to disappear from people's minds, or become so marginal that they do not much influence our overall society and culture.
So what "gives" society the right to coerce some of its members? That should be obviously not a well-formed question. Rights are not objects that can be given or received. Instead, people assert rights, and, if the right becomes sufficiently popular, begins to enforce it. People create rights, such as the right to not be murdered, because they want to live in safety. People create the government's right to tax themselves and their neighbors because they want public goods such as roads, bridges, schools, police, etc., and they want to manage the allocation of resources by taxation, because they believe that's the most effective and efficient way to obtain those public goods. Indeed we can say that a society, as opposed to some random collection of people, is defined by the rights its members hold in common.
Rights are social constructs, they are aggregate statistical features of the minds of people in a society. In any society, but especially in large societies such as most modern nations, none of these social constructs are assented to by everyone. Societies, therefore, create "meta-rights": what rights must an individual affirm to remain a member of society. These meta-rights range from the absolute (enthusiastically affirm every right in word or deed or die) to the pluralistic (some rights demand conformance in behavior or suffer punishment or death, but verbal dissent does not remove one from the society), with many gradations in that range.
Since rights are social constructs, any individual can challenge a right merely on his or her own preference. If you would prefer we manage our society without taxation, you may, in a pluralistic society such as our own, speak out and say so with neither permission nor legal consequence, on no authority but your own. The rub is, of course, that to change a right, which is a social construction, you must not only dissent from it, but convince enough other people to dissent from the right that it becomes socially "unconstructed." Thus, we socially constructed, for example, that alcohol was bad, and unconstructed the right to consume alcohol, and constructed the right for the government to punish people who bought, sold, transported or consume alcohol. Thirteen years later, we decided that was a bad idea, and reconstructed the individuals' right and unconstructed the government's right.
But what if "the people" socially construct an "unjust" right? Suppose, for example, they decided that freedom of speech was no longer either a shared preference nor a valid legal principle? Wouldn't they be mistaken, in the same sense that, for example, people who do not admit the scientific validity of evolution are just mistaken? Isn't it true in some sense that freedom of speech is a "natural" right?
Under an objectivist view, a natural right is a right that is true even if everyone were to believe it false, in again exactly the same way that evolution was true even when everyone believed it false, and in the same sense that some profound new theory of physics we may discover in a hundred years is true today even though today no one believes it. But this view is epistemically problematic. How could we know such a natural right? We cannot know it by scientific means. We know that a scientific law is actually true by never observing an exception, but of course we observe people contravening even those rights that we do hold, much less those we do not hold (because no one believes them). It seems that the only way to hold this kind of natural right as true is by divine or mystical revelation.
In the subjectivist view, a "natural" right is one that most people actually hold, due in some sense to the more-or-less fundamental biological or cultural evolution of our minds, or a right that is more consistent than its opposite with other rights that most people actually hold. A right that almost no one holds is not presently a natural right, but if human nature changes (and we are changing, biologically and culturally; change is inevitable), it might become a natural right.
We talk about the difference between natural and legal rights simply because historically, many governments have functioned with only minimal popular legitimacy. These governments regularly operated in ways that shocked the consciences of its own populace. The government didn't abridge an objectively true right, it abridged the subjective sensibilities of its own people.
I think this subjective view of rights accords more closely with history. Our changing views of rights, governments, ethics, are, unlike science, not a matter of conforming more and more closely with objective truth but a matter of reflecting how our culturally- and socially-constructed minds decide what kind of society we actually prefer, and how those preferences change over time.