 Phenomenalism has been defended as a doctrine about language, about facts, and about things. Taken in this last sense, it attempts to “reduce material objects to sensa, that is, to explain them as consisting solely of sensa or as being primarily groups or patterns of them” (Hirst 2006: 271). We might substitute the terms “sense-data”, “sensations”, “percepts”, “experiences”, etc. for Hirst’s term “sensa”. The worry is always the same: the basic entities of neutral monism are not neutral but mental. Hence neutral monism is a form of purely mentalistic metaphysics. It is true that traditional neutral monism is stated in terms of sensations (Mach), pure experience (James), and sensations and percepts (Russell). But, as used by the neutral monists, these terms are supposedly purged of their usual mental dimension. In the neutral monist framework, the predicates “mental” and “physical” apply solely to groups of neutral entities. To call a particular element—a sensation, a percept, a bit of pure experience—mental or physical is to speak elliptically: it is to say that this neutral entity is a constituent of a group of elements that, taken as a whole, is mental or physical. Moreover, neutral monism is not limited to those entities that are sensations and perceptions—this is particularly clear in the case of Mach and Russell. The existence of vast majority of neutral entities is inferred from the minute set of elements that are sensations and perceptions. These inferred elements are outside of all minds (see especially section  4.3.3  above). These are the strong anti-phenomenalist claims that neutral monism makes. How successfully the various neutral monists defend these claims is, of course, a difficult further question.