When we make ethical claims, we invoke a kind of objective authority. A familiar worry about our ethical practices is that this invocation of authority involves a mistake. This worry was perhaps best captured by John Mackie, who argued that the fabric of the world contains nothing so queer as objective authority and thus that all our ethical claims are false. Kantians such as Christine Korsgaard and David Velleman offer accounts of the objectivity of ethics that do without the controversial realist assumptions which gives rise to Mackie’s skepticism. They contend that our ethical claims correctly invoke objective authority not by corresponding to some normative pocket of the fabric of reality, but rather by expressing commitments that are i...