 There are two more recent developments in semantic theory that can been used to identify and defend a concept of narrow content. One of these is two-dimensional semantics and its application to the contents of propositional attitudes (Lewis 1981, Jackson 2007, and Chalmers 2012). Chalmers, for example, argues that a generalized 2D semantic framework can be used to isolate an a priori aspect of meaning that will be shared by you and your twin. You and your twin, on this view, always have a priori access to the truth-conditions of your own thoughts or sentences. If correct, this entails that there is a type or component of content that is not vulnerable to twin earth manipulation and so might qualify as narrow.