 Traditional neutral monism has been characterized as a form of reductionism or constructionism. The reductionist version of neutral monism takes mental and physical phenomena to be identical with groups of neutral entities. Russell’s constructionist version of the doctrine contents itself with the claim that there are logical constructions of neutral entities that play the roles of physical and mental entities; whether there also are mental and physical entities, as originally conceived, is a question that the constructionist does not address. Neutral monism differs from other versions of reductionism/constructionism by insisting on the neutrality of the basis. And its reductive/constructionist spirit sets it apart from the certain versions of nonreductive theories (about the mental) with which it is occasionally confused or identified. Panpsychism, phenomenalism, emergentism, and the dual aspect theory (sometimes understood as property dualism) are the leading candidates. And recently a number of philosophers have argued that neutral monism—in its traditional form as well as in its new Russellian monist form—is best interpreted as a nonstandard version of physicalism.