George Edward Moore is among this century's most influential philosophers. Perhaps best known for his "defense of common sense," he also made important contributions to metaphysics and theory of knowledge. But it is in ethics, and especially owing to the positions he develops in his Principia Ethica, first published in 1903, that his ideas have had their most enduring influence.A forerunner to this famous work, The Elements of Ethics is a series of ten unpublished lectures that were presented by Moore, then in his mid-twenties. The Elements shows that Principia Ethica did not spring fully-formed from Moore's pen but evolved slowly over time. In these lectures, Moore begins with the same question he asks in Principia Ethica: What is Good? Importantly, his answer is the same one he offers in Principia and many of its supporting arguments also appear, though sometimes in embryonic form. Moreover, in these lectures we also find sustained critiques of those who commit the "naturalistic fallacy," and of John Stuart Mill's commission of it in particular.In The Elements, however, Moore's position regarding ethics in relation to conduct differs in important respects from the one presented in Principia, and the former work contains important discussions, ranging from Christian ethics and the possibility of free will, not found in the latter.

This study of G. E. Moore’s work in moral philosophy draws upon a close examination of the early essays that preceded the writing of Principia Ethica in order to ground the author’s view that Moore’s famous "naturalistic fallacy argument" of Principia has been widely misunderstood. At the time of his death in 1986, Robert Peter Sylvester was in the process of preparing this book for publication. That process has been brought to completion by Ray Perkins, Jr., and R. W. Sleeper. Sylvester’s reappraisal of the moral philosophy of G. E. Moore argues that criticism of the work of this major twentieth-century British philosopher has been based on misinterpretation of his unified position. He treats Moore’s ideas about "What is Good?", "What things are Good?" and "What ought we to do?" as forming a coherent system. 

To bring this work up to date since the author’s death, the editors have provided a bibliographic essay following each chapter in which recent scholarship is discussed.