 At the second stage (sentence-level linguistic meaning), Lewis  (1969;  1975) had developed an analysis on which a Language is used by a population just in case certain conventions prevail in that population, for example a convention not to utter a sentence unless one believes the proposition to which it is mapped by that Language; semantic indeterminacy arises when the conventions are less than fully specific. Claims about conventions were in turn analysed in terms of patterns of credences and preferences among the members of the population. At the third stage (subsentential meaning), Lewis  (1975)  proposed that an interpretation function (or “grammar”) is admissible for a population just in case it is a “best” interpretation whose restriction to sentences is a Language the population uses. This paper suggests that the relevant notion of “bestness” may be lacking in clarity and objectivity, and that there will typically be many different best grammars, with the result that semantic indeterminacy at the subsentential level is pervasive. After embracing naturalness in Lewis  1983,  Lewis would presumably have cashed out the “bestness” relevant for the third stage in naturalness-theoretic terms, and consequently been less pessimistic about this part of the program, although he never spells this out explicitly. Lewis (1992)  also modifies his account of the second stage, appealing to naturalness to address a worry raised by Hawthorne  (1990).  The worry was that the original theory would assign incorrect interpretations to certain sentences where—e.g. because they are too long—hearing someone assert them would not tend to increase hearers’ confidence in the proposition that is in fact the correct interpretation. The fix gives some admissibility-constituting weight to eligibility (naturalness), to allow for extrapolation from the core cases covered by the convention-constituting pattern of credences and preferences.[52]