At the centre of the metaethical debate that took off from G.E. Moore's Principia Ethica (1903) was his critique of ethical naturalism. While Moore's own arguments against ethical naturalism find little acceptance these days, an alternative ground for thinking that ethical properties and facts could not be natural has gained prominence: No natural account can be given of normativity. This collection contains original essays from both sides of the debate. Representing a wide range of metaethical views, the authors develop diverse accounts of normativity and discuss what it means for a concept to be natural. Contributions are by Norbert Anwander, David Copp, Neil Roughley, Peter Schaber, Thomas Schmidt, Tatjana Tarkian, and Theo van Willigenburg.