 The truth conditions of sentences sometimes vary with the context of use. Thus, whether I am happy is true, depends on who the speaker is; other examples include the referents of here and this. Montague (1968; 1970b) addressed these factors, indicating that they could be treated by introducing additional parameters besides the time and the possible world. Despite occasional critcism (Cresswell 1973, 111; Lewis 1980, 86f.), the treatment of contextual dependence by way of a fixed finite list of parameters has become quite standard in formal semantics.