1 Indispensability Arguments in Metaethics: Even Better than in Mathematics? David Enoch In the debate over Mathematical Platonism, indispensability arguments have been a focus of attention for decades. We have reason to believe in whatever entities our best scientific theories quantify over, the thought seems to be. And they quantify not just over concrete, physical objects, but over abstract, mathematical ones too. So we have reason to believe that they too exist. Such arguments have been controversial from the start, of course, and their details too remain controversial. But all nominalists, as far as I know, at least agree that if nominalism is to be defended, something must be said by way of a response to the indispensability argument (however exactly it is understood). In metaethics, though, things have been different. Indeed, the metaethical thoughts most closely related to the indispensability arguments in science and mathematics seemed to have pulled in the opposite direction – because normative or moral facts and properties did not seem to play an indispensable role in any scientific theory, or, for that matter, in any other respectable explanation, we did not have reason to believe they existed. Rather than supporting realism (in some version, presumably the metaethical analogue of Mathematical Platonism), thoughts about indispensability seemed to challenge it 1 . Some – most – realists have responded by insisting that normative facts do play an appropriate explanatory role. Whether this is so – and what it takes for a role to be appropriate, and what follows if it is – remains a live, controversial topic, as can be seen from some of the contributions in this volume 2 . In previous work 3 , though, I pursued a different line: I have been 1 Harman (1977, Chap 1). 2 For some examples, see Sayre-McCord (1988; 1992); Shafer-Landau (2003, 98-115); Sturgeon (1984; 1986; 1991; 1992; 1998).