After the publication of Moore’s Principia Ethica, naturalism in Britain was given up for dead. The first attempts to revive it were made in the late 1950s by Philippa Foot and Elizabeth Anscombe (1919–2001). In response to Hare’s intimation that anything could be a moral principle so long as it satisfied the formal requirement of universalizability in his sense, Foot and Anscombe urged that it was absurd to think that anything so universalizable could be a moral principle; the counterexample they offered was the principle that one should clap one’s hands three times an hour. (This principle is universalizable in Hare’s sense, because it is possible to hold that all actions relevantly similar to it are right.) They argued that perhaps a moral principle must also have a particular kind of content—that is, it must somehow deal with human well-being, or flourishing. Hare replied that, if “moral” principles are limited to those that maximize well-being, then, for anyone not interested in maximizing well-being, moral principles will have no prescriptive force.
This debate raised the issue of what reasons a person could have for following a moral principle. Anscombe sought an answer to this question in an Aristotelian theory of human flourishing. Such a theory, she thought, would provide an account of what any person must do in order to flourish and so lead to a morality that each person would have a reason to follow (assuming that he had a desire to flourish). It was left to other philosophers to develop such a theory. One attempt, Natural Law and Natural Rights (1980), by the legal philosopher John Finnis, was a modern explication of the concept of natural law in terms of a theory of supposedly natural human goods. Although the book was acclaimed by Roman Catholic moral theologians and philosophers, natural law ethics continued to have few followers outside these circles. This school may have been hindered by contemporary psychological theories of human nature, which suggested that violent behaviour, including the killing of other members of the species, is natural in human beings, especially males. Such views tended to cast doubt on attempts to derive moral values from observations of human nature.
As if to make this very point, another form of naturalism arose from a very different set of ideas with the publication of Sociobiology: The New Synthesis (1975), by Edward O. Wilson, followed subsequently by the same author’s On Human Nature (1978) and Consilience: The Unity of Knowledge (1999). Wilson, a biologist rather than a philosopher, claimed that new developments in the application of evolutionary theory to social behaviour would allow ethics to be “removed from the hands of philosophers” and “biologicized.” He suggested that biology justifies specific moral values, including the survival of the human gene pool, and—because humans are mammals rather than social insects—universal human rights.
As the previous discussion of the origins of ethics suggests, the theory of evolution may indeed reveal something interesting about the origins and nature of the systems of morality used by human societies. Wilson, however, was plainly guilty of breaching Hume’s dictum against deriving an “ought” from an “is” when he tried to draw ethical conclusions from scientific premises. Given the premise that human beings wish their species to survive as long as possible, evolutionary theory may indicate some general courses of action that humankind as a whole should pursue or avoid; but even this premise cannot be regarded as unquestionable. For the sake of ensuring a better life, it may be reasonable to run a slight risk that the species does not survive indefinitely; it is not even impossible to imagine circumstances in which life becomes so grim that extinction should seem a reasonable choice. Whatever these choices may turn out to be, they cannot be dictated by science alone. It is even less plausible to suppose that the theory of evolution can settle more specific ethical questions. At most, it can indicate what costs humankind might incur by pursuing whatever values it may have.
Very different and philosophically far more sophisticated forms of naturalism were later proposed by several philosophers, including Richard B. Brandt, Michael Smith, and Peter Railton. They held that moral terms are best understood as referring to the desires or preferences that a person would have under certain idealized conditions. Among these conditions are that the person be calm and reflective, that he have complete knowledge of all the relevant facts, and that he vividly appreciate the consequences of his actions for himself and for others. In A Theory of the Good and the Right (1979), Brandt went so far as to include in his idealized conditions a requirement that the person be motivated only by “rational desires”—that is, by the desires that he would have after undergoing cognitive psychotherapy (which enables people to understand their desires and to rid themselves of those they do not wish to keep).
Do these forms of naturalism lead to an objectivist view of moral judgments? Consider first Brandt’s position. He asked: What rules would a rational person, under idealized conditions, desire to be included in an ideal moral code that all rational people could support? A moral judgment is true, according to Brandt, if it accords with such a code and false if it does not. Yet, it seems possible that different people would desire different rules, even under the idealized conditions Brandt imagined. If this is correct, then Brandt’s position is not objectivist, because the standard it recommends for determining the truth or falsity of moral judgments would be different for different people.
In The Moral Problem (1994) and subsequent essays, Smith argued that, among the desires that would be retained under idealized conditions, those that deserve the label “moral” must express the values of equal concern and respect for others. Railton, in Facts, Values and Norms: Essays Toward a Morality of Consequence (2003), added that such desires must also express the value of impartiality. The practical effect of these requirements was to make the naturalists’ ideal moral code very similar to the principles that would be legitimized by Hare’s test of universalizability. Again, however, it is unclear whether the idealized conditions under which the code is formulated would be strong enough to lead everyone, no matter what desires he starts from, to endorse the same moral judgments. The issue of whether the naturalists’ view is ultimately objectivist or subjectivist depends precisely on the answer to this question.
Another way in which moral realism was defended was by claiming that moral judgments can indeed be true or false, but not in the same sense in which ordinary statements of fact are true or false. Thus, it was argued, even if there are no objective facts about the world to which moral judgments correspond, one may choose to call “true” those judgments that reflect an appropriate “sensibility” to the relevant circumstances. Accordingly, the philosophers who adopted this approach, notably David Wiggins and John McDowell, were sometimes referred to as “sensibility theorists.” But it remained unclear what exactly makes a particular sensibility appropriate, and how one would defend such a claim against anyone who judged differently. In the opinion of its critics, sensibility theory made it possible to call moral judgments true or false only at the cost of removing objectivity from the notion of truth—and that, they insisted, was too high a price to pay. Kantian constructivism: a middle ground?