 One way to introduce the structuralist approach is to see it as a development of the theory conception formulated above. On the theory view, a property is physical just in case it is tied in the right way to a physical theory. One problem that arises for such a view, as we have seen, is what ‘physical theory’ is supposed to mean here. For the structuralist (at least in the context; ‘structuralism’ can mean many different things), a physical theory is one that employs a restricted vocabulary. One particularly frank version of this sort of view is suggested by Russell 1927; on this view, the vocabulary in question is restricted to logical or mathematical vocabulary. Contemporary philosophers adopt a less restricted view according to which the vocabulary is either logical or mathematical or causal or nomological (i.e. pertaining to laws) or some combination of these (see Alter 2016, Chalmers 2020, Goff 2017; for criticism see Stoljar 2020). In effect, proposals like this provide a topic-neutral conception of the physical, and hence a topic-neutral conception of physicalism.