 Russell’s destiny as an ethical thinker was dominated by one book—G.E. Moore’s Principia Ethica (1903). Before 1903, Russell devoted some of the energy that he could spare from German Social Democracy, the foundations of mathematics and the philosophy of Leibniz to working out a meta-ethic of his own. After 1903, he became an enthusiastic but critical convert to the doctrines of Principia Ethica (though there is some evidence that the conversion process may have begun as early as 1897). Moore is famous for the claim, which he professes to prove by means of what has come to be known as the Open Question Argument, that there is a “non-natural” property of goodness, not identical with or reducible to any other property or assemblage of properties, and that what we ought to do is to maximize the good and minimize the bad. Russell subscribed to this thesis—with certain important reservations—until 1913. Thereafter he continued to believe that if judgments about good and bad are to be objectively true, non-natural properties of goodness and badness are required to make them true. It is just that he ceased to believe that there are any such properties. Does this mean that judgments about good and evil are all false? Not necessarily (though Russell did subscribe to that view for a brief period during 1922). An alternative theory is that moral judgments are neither true nor false, since their role is not to state facts or to describe the way the world is, but to express emotions, desires or even commands. This (despite some waverings) was Russell’s dominant view for the rest of his life, though it took him twenty-two years to develop a well worked-out version of the theory. He tended to call it subjectivism or “the subjectivity of moral values” though it is nowadays known as non-cognitivism, expressivism or emotivism. He came to think that, despite their indicative appearance, moral judgments—at least judgments about what is good or bad in itself—are really in the optative mood. (A sentence is in the optative mood if it expresses a wish or a desire.) What “X is good” means is “Would that everyone desired X!”. It therefore expresses, but does not describe, the speaker’s state of mind, specifically his or her desires, and as such can be neither truth nor false, anymore than “Oh to be in England now that April’s here!”. If I say “Oh to be in England now that April’s here!”, you can infer that I desire to be in England now that April’s here (since absent an intention to mislead, it is not the sort of thing I would say unless I desired to be in England and thought that April was here). But I am not stating that I desire to be in England, since I am not stating anything at all (except perhaps that April is here). (See RoE: 131–144/Religion and Science: ch. 9.) Although this was Russell’s dominant view from 1913 until his death, he did not care for it very much.