One-Person Moral Twin Earth Cases

This paper presents two cases demonstrating that theories allowing the environment to partially determine the content of moral concepts (such as the causal theory of reference) that provide incorrect truth-conditions for moral terms. While typical Moral Twin Earth cases seek to establish that these theories fail to account for moral disagreement, neither case here essentially involves interpersonal disagreement. Both involve a single person retaining moral beliefs despite recognizing actual or potential mismatches with the purportedly content-determining facts. This lets opponents of such theories grant objections that standard Moral Twin Earth cases fail to demonstrate disagreement, and argue more straightforwardly that they generate implausible truth-conditions for moral claims.