 Content externalism is typically understood as a claim of dependent possession which is, in turn, grounded in a more basic claim of individuation dependence. The idea of dependent possession is straightforward: whether or not an individual can entertain the content that p (for example, by having a belief, thought, desire or other propositional attitude with this content) depends on the nature of that individual’s environment (and facts about its relation to that environment). It is not possible for an individual to entertain this content unless the environment contains the requisite objects, properties, facts, events etc. of a certain sort (McGinn 1989). Content externalism is the claim that, at least in some cases, though not necessarily all, the possession of a mental state with a given content is environmentally dependent in this sense.