 Some philosophers suggest that ‘physicalism’ is distinct from ‘materialism’ for a reason quite unrelated to the one emphasized by Neurath and Carnap. As the name suggests, materialists historically held that everything was matter — where matter was conceived as “an inert, senseless substance, in which extension, figure, and motion do actually subsist” (Berkeley, Principles of Human Knowledge, par. 9). But physics itself has shown that not everything is matter in this sense; for example, forces such as gravity are physical but it is not clear that they are material in the traditional sense (Lange 1865, Dijksterhuis 1961, Yolton 1983). So it is tempting to use ‘physicalism’ to distance oneself from what seems a historically important but no longer scientifically relevant thesis of materialism, and related to this, to emphasize a connection to physics and the physical sciences. However, while physicalism is certainly unusual among metaphysical doctrines in being associated with a commitment both to the sciences and to a particular branch of science, namely physics, it is not clear that this is a good reason for calling it ‘physicalism’ rather than ‘materialism.’ For one thing, many contemporary physicalists do in fact use the word ‘materialism’ to describe their doctrine (e.g. Smart 1963). Moreover, while ‘physicalism’ is no doubt related to ‘physics’ it is also related to ‘physical object’ and this in turn is very closely connected with ‘material object’, and via that, with ‘matter.’ 