Introduction: Physicalism – the claim that everything is physical – has been the dominant position in philosophy of mind since at least the middle of the twentieth century. Nonetheless, physicalism has long been accused of being unable to account satisfactorily for the qualitative or subjective aspect of experience, for example, the reddishness of one ‘ s visual experience of a ripe tomato or the painfulness of one ‘ s tactile experience of a sharp object. Many have charged that it is dif? cult to see how these aspects of experience could be accounted for in solely physical terms. Focusing speci? cally on the experi- ence that a bat has when using its sonar, Thomas Nagel formulated this charge in a particularly powerful way. His argument is designed to show that subjective facts about experience, which are essential to it, cannot be captured in the objective language of physicalism. Although most philoso- phers assume that the argument, if successful, would show that physicalism is false, Nagel himself is careful to claim only that we currently lack the conceptual resources to see how physicalism could be true.