It is an interesting question whether Russellian monism is necessarily opposed to physicalism rather than a special case of it (Montero 2015, Brown 2017). In any case, we should note that Russellian monism is designed to conform to the causal (or determinational) closure of the physical realm, as indeed are epiphenomenalism and overdeterminationism. It is striking that nearly all contemporary views of the mind-brain relations are naturalist at least to the extent that they respect this closure thesis. Strongly interactionist views that allow the conscious mind to make an independent difference to the physical world have few defenders nowadays (but see Lowe 2000, 2003; Steward 2015).