‘Moral Twin Earth’ thought experiments constitute a central semantic challenge to naturalistic normative realism. This paper first outlines a general framework for understanding the challenge, according to which (i) central

normative terms are semantically stable in ways that contrast with many other paradigmatic descriptive terms, and (ii) realists should expect to have a unified meta-semantic theory that explains the difference in stability between the normative and descriptive terms in question. The most attractive way of meeting this challenge, we argue, appeals to the idea of reference magnetism. According to this influential idea, some properties are reference magnets, which (roughly) means that they are comparatively easy to refer to. We argue that (together with other plausible assumptions) reference magnetism can provide an attractive explanation of both the general phenomenon of varying semantic stability, and the distinctive semantic stability of normative terms. We illustrate this by showing that reference magnetism can smoothly vindicate plausible judgments about Moral Twin Earth cases. We conclude by offering an alternative gloss on our account, for those wary of the metaphysical

commitments we propose. The alternative account adapts our proposal to provide a debunking explanation of the apparent semantic stability of normative terms.