In “The Nature of Judgment” (1899), G. E. Moore defends the strange thesis according to which “[i]t seems necessary… to regard the world as formed of concepts”. Philosophers have offered distinct understandings of this proposal, in particular of what Moorean concepts really are. In this article I discuss and reject three of them: one, according to which Moorean concepts are universals within the framework of a bundle theory of concrete particulars (Nelson, 1962; Baldwin, 1990); a second one, according to which Moorean concepts are particulars within a mereological framework of analysis (Bell, 1999); and a third one, according to which Moorean concepts are a sui generis category, resulting from his alleged rejection of the substance (particu...