 The unifying inspiration for causal theories of mental content is that some syntactic item “X” means X because “X”s are caused by  Xs.[5]  Matters cannot be this simple, however, since in general one expects that some causes of “X” are not among the content-specifying causes of “X”s. There are numerous examples illustrating this point, each illustrating a kind of cause that must not typically be among the content-determining causes of “X”: