Justifying Reasons, Motivating Reasons, and Agent Relativism in Ethics

According to agent relativism, each person's moral requirements are relative to her desires or interests. That is, whether a person morally ought to depends on what interests or desires she has. Some philosophers charge that the main argument for agent relativism trades on an ambiguity –specifically, an ambiguity in ``reason,' ``reasonfor action,' or a kindred term. This charge has been common, and widely thought to damage the case for agent relativism, since its appearance, in 1958, in a now classic paper by William Frankena. In what follows I examine the charge in detail, showing that insofar as it aims to discredit the argument for agent relativism, it fails in its purpose.