More weighty is the claim that to make human nature the basis for ethics is to accept something unacceptably constricting: the imposition of a single form of life and preferred set of dispositions on everyone. Nagel is right that we have reason to reject this picture; from the viewpoint of my own deliberations I know that an ethical theory cannot be right that would impose a single way of life on me and everyone else just on the grounds that we are human.

However, what is this ‘singleness’ of the ethical way of life grounded in human nature? Nagel and many other modern critics clearly think that it is something which constrains the range of specific activities in a single life and implies that individuals, however diverse, should aim at the same specific goal. If this were the case, criticism would be easy; but it is not how we find the actual ancient appeal to nature functioning. We have already seen that reflecting on our final end does not prescribe one range of specific human activities against another. The importance of reflecting on my life as a whole lies in the opportunity for clarifying and rethinking my priorities and the ordering of my values. To be told that one way of doing this, as opposed to another, is natural, in accordance with human nature, is to be told two things. One is that there are constraints which my reflection must respect and priorities which are not up to me to settle. If it is true, for example, that human nature is so constituted as always to seek only pleasure, then this rules out certain theories as to how I should live—the Stoic and Aristotelian, for a start. It also directs me as to where to discover mistakes in my life. If it is true that I cannot help seeking pleasure in all I do, and if I do not seem to be very successful in this, then I must be making mistakes as to what pleasure is and how to achieve it; and searching for these mistakes, and rectifying them, is bound to revise my way of life.

But the appeal to nature is also an appeal to an ideal, an ethical ideal, articulated by ethical theory, in terms of whic hI can locate, criticize and modify those elements in my ethical beliefs which rely merely on convention. For beliefs which I have acquired in an uncritical way from my social environment cannot be relied on to take me in the righ tdirection; indeed (depending on how revisionary the theory in question is) they can be taken to be faulty and misleading. Appealing to nature gives me an ethical ideal in terms of which to reject those of my beliefs which turn out to conflict with it, and better to understand those beliefs which are in fact in conformity with it. For what is natural about me is objectively so, whereas many of my beliefs may rest on nothing better than convention. But we plainly do not, just from a conception of human nature (as aiming for pleasure, say) conclude that we should all do the same specific things in life.

Ancient theories, then, do not use the appeal to nature to establish a single specific way of life, or to encourage people to ignore their individual differences.

From The Morality of Happiness, by Julia Annas. I’m not a fan of how she uses the word “values” here, but in context she makes it clear it’s not the same thing as subjective valuation, which is what we typically associate with the word today.

See Daniel Russell on why the nature-as-ideal is necessary in ethics, and how it works in practice.

This post also provides further exploration of naturalism of this sort.