 But language use exhibits several problematic features that must be accommodated: indexicality, context sensitivity, ambiguity, etc. To properly account for these features, the relevant meaning functions must take several variables as arguments. It will not be a simple one-to-one mapping from sentence to meaning, but a more complex mapping of a sentence together with a speaker, a time, a world, and what have you, onto a corresponding meaning. Lewis is aware of this, and includes it as part of what L should be like if it is to be used by P. So long as members of P know this about L, and use it while abiding by the conventions of truthfulness and trust, there should be no serious trouble. (To say that speakers know this is not to say that they can, upon request, explicitly describe how it is that L works, but to say that they have implicit knowledge of L, such that they can successfully use L to communicate with and understand other members of P.) Lewis calls the situation of a language’s being realized in this way a “perfect case of normal language use”. That is, it is at best an idealization in need of refinement. Chomsky and Davidson (below) can be thought of as in different ways suggesting that the conceptualization offered here of language and its realization is fundamentally mistaken and not merely a rough draft.