 Lewis’s solution to this puzzle relies on his theory of natural properties, described below in Section 4.6. He argues that some grammars (in the above sense of grammar) are more natural than others. By default, we speak a language with a natural grammar. Since L has a natural grammar, and L* doesn’t, other things being equal, we should be interpreted as speaking L rather than L*. Even if other things are not quite equal, i.e. we don’t naturally trust speakers of very long sentences, if there is a convention of truthfulness and trust in L in the vast majority of verbal interactions, and there is no other language with a natural grammar in which there is a convention of truthfulness and truth, then the theory will hold, correctly, that we do speak L.