This introduction provides a highly readable critical overview of the main arguments and themes in twentieth-century and contemporary metaethics. It traces the development of contemporary debates in metaethics from their beginnings in the work of G. E. Moore up to the most recent arguments between naturalism and non-naturalism, cognitivism and non-cognitivism. A highly readable critical overview of the main arguments and themes in twentieth century and contemporary metaethics. Asks: Are there moral facts? Is there such a thing as moral truth? Is moral knowledge possible? Traces the development of contemporary debates in metaethics from their beginnings in the work of G. E. Moore up to the most recent debates between naturalism and non-naturalism, cognitivism and noncognitivism. Provides for the first time a critical survey of famous figures in twentieth century metaethics such as Moore, Ayer and Mackie together with in-depth discussions of contemporary philosophers such as Blackburn, Gibbard, Wright, Harman, Railton, Sturgeon, McDowell and Wiggins.