Online Papers - Brian Weatherson

David Lewis 88
7.5 Ethics
Lewis is obviously not as well known for his work in ethics as for his work in other
areas of philosophy. It was something of a surprise when one of the volumes of his
collected papers was called Papers in Ethics and Social Philosophy (2000). On the other
hand, the existence of this volume indicates that there is a large body of work that
Lewis put together in moral philosophy, very broadly construed. The best guide to
this work is chapter 8 of Nolan (2005), and I’ll follow Nolan very closely here.
As Nolan suggests, the least inaccurate summary of Lewis’s ethical positions is
that he was a virtue ethicist. Indeed, a focus on virtue, as opposed to consequences,
plays a role in his defence of modal realism, as we saw in section 6.4. Nolan also
notes that this position is somewhat surprising. Most philosophers who accept views
related to Lewis’s about psychology and decision-making (in particular, who accept
a Humean story about beliefs and desires being the basis for motivation, and who
accept some or other version of expected utility maximisation as the basis for rational
decision) have broadly consequentialist positions. But not Lewis.
Lewis was also a value pluralist (1984a; 1989b; 1993a). Indeed, this was part of
his objection to consequentialism. He rejected the idea that there was one summary
judgment we could make about the moral value of a person. In “Reply to McMichael”
(1978a) he complains about the utilitarian assumption that “any sort or amount of
evil can be neutralized, as if it had never been, by enough countervailing good —and
that the balancing evil and good may be entirely unrelated” (1978a, 85).
In meta-ethics, Lewis defended a variety of subjectivism (1989b). Like many subjectivists,
Lewis held that something is valuable for us iff we would value it under
ideal circumstances. And he held, following Frankfurt (1971), that valuing something
is simply desiring to desire it. What is distinctive about Lewis’s position is his
view about what ideal circumstances are. He thinks they are circumstances of “full
imaginative acquaintance”. This has some interesting consequences. In particular, it
allows Lewis to say that different goods have different conditions of full imaginative
acquaintance. It might, he suggests, be impossible to properly imagine instantiating
several different values at once. And that in turn lets him argue that his value
pluralism is consistent with this kind of subjectivism, in a way that it might not be
consistent with other varieties of subjectivism.
Lewis also wrote several more papers in applied ethics. In two interesting papers
on tolerance (1989a; 1989c), he suggests that one reason for being tolerant, and
especially of being tolerant of speech we disapprove of, comes from game-theoretic
considerations. In particular, he thinks our motivation for tolerance comes from
forming a ‘tacit treaty’ with those with differing views. If we agree not to press our
numerical superiority to repress them when we are in the majority, they will do the
same. So tolerating opposing views may be an optimal strategy for anyone who isn’t
sure that they will be in the majority indefinitely. In these works it is easy to see
the legacies of Lewis’s early work on philosophical lessons to be drawn from game
theory, and especially from the work of Thomas Schelling.