G. E. Moore's Principia Ethica, which was first published in 1903, has had an extraordinary influence on twentieth-century moral philosophy. One of its ideas - the naturalistic fallacy - provoked Stephenson, Ayer, and the other expressivists, who provoked the growth of metaethics into a vast and elaborate field of professional philosophical concern.
This review isn't about that field: I want instead to make some ideological or sociological remarks on Moore's project and legacy.
As I read it, Principia Ethica is an attempt to found an autonomous form of moral philosophy, immune to being absorbed by the sciences, especially biology (which in the late nineteenth and early twentieth centuries was bullish post-Darwin) and psychology (post-William James). This explains several odd features of the text and its reception: the extraordinary vitriol it directs against Herbert Spencer and John Stuart Mill - neither of whom could have cared less whether what they were doing counted as philosophy in Moore's idiosyncratic sense. Its firm assertion of distinctive, non-empirical methods for philosophy: intuition, self-evidence, and the method of absolute isolation. In person, as John Maynard Keynes records in his fascinating memoir 'My Early Beliefs', Moore's methods were expressed as pantomimes of extreme disbelief that anyone could possibly disagree with him. Finally, the cultish character of Moore's school at Cambridge, also described by Keynes.
Moore won: in the twentieth century, philosophy became professionalised in university philosophy departments, jealous of their distinctive subject-matter. Philosophers' research was funded on models borrowed from the sciences, along with that word, 'research': I work in philosophy by reading, thinking about, talking about, and writing it, but I'm not sure I do research. Philosophy's superstars were the magicians of the abstract and technical - like metaethics - and their work appeared in obscure, overpriced professional journals; popularisers and amateurs were looked on with suspicion, however many books they sold. (There's a fair amount of exaggeration in this picture, I admit.)
Was this a good thing? Obviously I owe my living to it, so I'm not disinterested (I'm no superstar, but I've published in several of those overpriced journals). But with that caveat, I'm in two minds: on one hand, I think philosophy should be public and accessible. It's a shame that some of the smartest people in the field never talk outside it, not least because there's obvious public interest in the questions philosophers work on, and if the smart people don't publish for that public, they'll look elsewhere (to weak sauce like Alain de Botton, for example). On the other hand, the realistic alternative to professional philosophy right now is probably not a utopia of high-level public discourse; it's the replacement of philosophy with self-help (The Secret, for example), leavened with the occasional philosopher kept on staff by a wealthy patron: think of Thomas Hobbes's faintly embarrassing dedication of Leviathan to Francis Godolphin.