About some things, I'm a happy nominalist. Whether you consider a sapphire to be a species of ruby or a separate type of thing is, as far as I'm concerned, a matter of indifference and a matter of convention. Whether something is a hill or a mountain is also a matter of convention, as all of us know who have watched a rather boring movie with a rather long name starring Hugh Grant.
But there is one kind of nominalism that must be decisively rejected, and that is nominalism about human beings. Here are some quotes from a classic bit of nominalist nonsense about human beings:
Under this conception, the possession of dignity by humans signifies that they have an inherent moral worth. In other words, because human beings possess dignity we cannot do what we like to them, but instead have direct moral obligations towards them. Indeed, this understanding of dignity is also usually considered to serve as the grounding for human rights....If all human beings possess dignity–this extraordinary moral worth–we need some explanation of what it is about the species Homo sapiens that makes them so deserving. When we start looking at particular characteristics that might ground dignity – language-use, moral action, sociality, sentience, self-consciousness, and so on – we soon see that none of these qualities are in fact possessed by each and every human. We are therefore left wondering why all human beings actually do possess dignity....Obviously, given controversies over abortion, stem cell research, genetic interventions, animal experimentation, euthanasia and so on, bioethics does need to engage in debates over which entities possess moral worth and why. But these are best conducted by using the notion of ‘moral status’ and arguing over the characteristics that warrant possession of it. Simply stipulating that all and only human beings possess this inherent moral worth because they have dignity is arbitrary and unhelpful.
Yeah, gosh. If some individuals of a species lack a particular property, then obviously that property has nothing to do with the nature of the species, and we're just "left wondering" what could possibly bind the members of the species together or why we should treat some species differently from others. It's a poser, all right.
But of course, it isn't a poser. It's a no-brainer. If I say that man is a rational animal, of course that doesn't mean that I think every single human individual is a rational animal. It means that it's of the nature of man as a species to be rational. A human being who hasn't yet developed rationality or who has lost consciousness due to illness, age, or injury is still a member of the species whose nature it is to be rational animals when fully developed and not suffering privation. This is hard? It's no harder than knowing that a three-legged dog is still a dog. But it's too hard for some contemporary bioethicisists, including the ethicist Alasdair Cochrane, from whose article "Undignified Bioethics" the above quotations come.
Wesley J. Smith, who provides the quotations from Cochrane (only the abstract being available on-line), gets it. Here's Smith:
Those individuals who happen to lack those attributes have either not developed them yet (embryos, fetuses, infants), or have illnesses or disabilities that impede their expression. But those attributes are unique to the human species, they are uniquely part of our natures. That some have not developed, or have lost, them, is irrelevant...[Emphasis in original]
Smith then makes what might seem like a slight argumentative mis-step by bringing practical considerations into the essentialist debate. That is to say, he says that what he calls human exceptionalism must especially be upheld because of the consequences of rejecting it, in particular the return to "the pernicious thinking of eugenics and social Darwinism." One might say that the consequences of rejecting it are irrelevant to whether it is true. But I wouldn't accuse Smith of a mis-step. He understands that this is about the nature of man qua man, and he re-emphasizes this when he mentions "he uniqueness of human beings as the known universe’s only moral species." I think the point about the consequences of rejecting human exceptionalism can be thought of in terms of being given a chance to think again when we find our ideology leading us somewhere horrible. As I pointed out here, there needs to be such a thing as an ethical reductio for ideology. And I think that is Smith's point about consequences.
Meanwhile, color me essentialist when it comes to human beings. Nominalism about mankind is one kind of nominalism you must refuse