In the period from 1870 to 1914 there was a shift within moral philosophy towards meta-ethical concerns. Metaethics and its guiding idea that the first task in moral philosophy is an enquiry into the semantics of moral discourse and into its ontological foundations, though by no means an invention of twentieth-century philosophy, has become its most characteristic feature.

The history of twentieth-century ethics starts in Cambridge, where in 1903 G. E. Moore published Principia Ethica. It rarely happens, as it did with Principia Ethica, that one book accounts for so many of the later developments in a field. It was Moore’s declared intention to break sharply with the philosophical tradition. According to him, even the most prominent figures in the history of moral philosophy, for example, Aristotle, Kant, and Mill, have misunderstood the foundations of ethics. Too late to be of any influence on Principia Ethica, Moore thinks he has discovered a soul-mate. In the Preface to the first edition of Principia Ethica Moore writes: ‘When this book had been completed, I found, in Brentano’s Origins of the Knowledge of Right and Wrong opinions far more resembling my own, than those of any other ethical writer with whom I am acquainted’ (Moore 1903 [1993a: 36]).