 Third, these theories assume that it is possible to explain the origin of underived content without appeal to other semantic or contentful notions. So, it is assumed that there is more to the project than simply saying that one’s thoughts mean that Colleen currently has the measles because one’s thoughts are about Colleen currently having the measles. Explicating meaning in terms of aboutness, or aboutness in terms of meaning, or either in terms of some still further semantic notion, does not go as far as is commonly desired by those who develop causal theories of mental content. To note some additional terminology, it is often said that causal theories of mental content attempt to naturalize non-natural, underived meaning. To put the matter less technically, one might say that causal theories of mental content presuppose that it is possible for a purely physical system to bear underived content. Thus, they presuppose that if one were to build a genuinely thinking robot or computer, one would have to design it in such a way that some of its internal components would bear non-natural, underived content in virtue of purely physical conditions. To get a feel for the difference between a naturalized theory and an unnaturalized theory of content, one might note the theory developed by Grice (1948). Grice developed an unnaturalized theory. Speaking of linguistic items, Grice held that ‘Speaker S non-naturally means something by “X”’ is roughly equivalent to ‘S intended the utterance of “X” to produce some effect in an audience by means of the recognition of this intention.’ Grice did not explicate the origin of mental content of speaker’s intentions or audience recognition, hence he did not attempt to naturalize the meaning of linguistic items.