Clearly, normativity is natural, in that ethical rules or norms are based in human biological needs and innate psychological dispositions, modulated by culture.  However, in evaluating the rightness of these norms, we can only use as criteria some subset of these very same norms.  If we are ethical naturalists, there isn’t a value-free Archimedean point outside them from which we can determine which moral rules we ought to subscribe to.  Nor is there an independent moral reality outside human nature and culture that tells us what’s right.   In arguing about abortion or autonomy in dying, for instance, naturalists can only appeal to values already held by themselves and those they're trying to convince.  

Committed to science and empiricism as their way of knowing about the world, naturalists find no evidence for a transcendent being that could ground morality.  And if such a being existed, the same demands for justification could be posed to it: why are just these values the right ones, and not others?  The supernatural guarantor or source of ethics has to answer such questions, at the risk of being arbitrary.  And such answers would inevitably have to appeal to some of what we already hold to be true and good, otherwise they wouldn’t gain any purchase on us.  So appeals to external authority simply don’t get us anywhere in validating our ethical intuitions.  To suppose they do is to commit what might be called the supernaturalistic fallacy. 

Importantly, just because a norm bequeathed by human nature or culture happens to be the case at the moment doesn’t mean it necessarily should be the case. In a self-reflective culture such as ours, the force of the moral “should” attached to a norm doesn’t derive from its mere existence – to suppose it does would be to commit the naturalistic fallacy – but only issues from the process of explicit evaluation (although of course some norms are a lot less controversial than others).  In this way, shoulds or oughts, even though ultimately arising from what is, and therefore natural, aren’t a simple reading off of what is, but rather what’s left after the evaluative process.  The “value added” by evaluation of norms is that, if all goes well, we reach a rough reflective equilibrium of agreement about norms within a moral community, whether local, national, or international.  Such equilibrium, which in an open society necessarily admits of disagreement about many moral particulars, is the naturalistic analog and substitute for supernaturally derived moral absolutes.

The fact that the evaluative process itself inevitably makes use of some pre-existing norms, rooted in human nature and culture (for instance, the procedural norm that disagreements should be negotiated, not decided by force), bridges the sharp duality often supposed to exist between is and ought: norms are natural; they are naturally explicable facts about social creatures.  But that there is such an evaluative process, albeit an entirely natural one (since we are entirely natural creatures), insulates norms from, and deprives them of, the all too facile justificatory claim embodied in the naturalistic fallacy: that since something is, it should be. That we should avoid the naturalistic fallacy is itself a norm about justification that we’ve hit upon in resisting Social Darwinism and the various forms of “might makes right.”  So we can both explain moral rules as natural facts, yet still say some are more justified than others.

Human nature can’t of course be a direct guide to morality since we have selfish, nasty tendencies as well as cooperative, altruistic tendencies.  How, if we are naturalists, do we decide which tendencies to encourage, which to discourage, and in what proportion?  By reading the lessons of history, engaging in discourse with our peers, being persuaded and persuading others, and remembering that we’re all persons, with very much the same needs and dispositions.

This last point about our common personhood captures the basic moral presumption that’s characteristic of the current reflective equilibrium in liberal democracies: there are no privileged persons – we are presumptively equal in the eyes of morality and the law.  We are beneficiaries of the immensely precious cultural construction of an expanding definition of who counts as a person with a full complement of human rights; we now count women and minorities but didn’t 200 years ago. This notion of universal rights-bearing personhood also entails a vital procedural constraint on deciding normative questions themselves: they are to be debated, not decided by fiat of some privileged class of persons, since no such class exists.  Compared to earlier systems of deciding and enforcing norms, this constitutes considerable moral progress, even though on a naturalistic understanding of ourselves there are no external benchmarks to measure it. Equality itself is now the benchmark, we agree. 

The norms of equal personhood and persuasive discourse are of course not written in our genes, but they are consistent with our innate moral sense.  We can be taught to think of each individual as an end in herself, whose rights are co-equal with every other person’s, and that therefore they have an equal voice in the conversation about deciding what’s right.  And that teaching is the basis for some fairly successful cooperation and the satisfaction of many human needs and desires, which is why it has a moral claim on us (not that it couldn’t be improved, obviously).  On a naturalistic understanding of ourselves that discounts supernatural foundations for morality, it’s the beneficial consequences of a moral system that ultimately ratify it in the eyes of its subscribers.

There’s no guarantee, of course, that the liberal cultural consensus on equality of rights, including the right to participate in normative discourse, will survive.  Such are the perils of living without external moral guarantors, but these wouldn’t help us anyway.  Since we don’t want to commit either the supernaturalistic or naturalistic fallacy, we seek to justify our ethical intuitions to our peers – provide the oughts – all the while aware that this is a natural phenomenon – an is – taking place within the natural world.  That world supplies the motivational basis for ethics in our evolved human nature, but it can’t supply a further foundation to confirm the direction we should take in deciding moral questions. That’s the situation naturalists must admit we’re in, and it gives us far more responsibility for our norms than if we could simply crib them from commandments.

TWC, March 2006