Chapter 6 introduces the concepts relevant to speech act theory and discusses difficulties in the study of speech acts, both limitations of the form-to-function approach and obstacles to the function-to-form approach; it then reviews the work-arounds suggested in the literature, including the use of illocutionary-force-indicative devices, of typical syntactic patterns for different speech acts, and of metacommunicative labels. After looking at several studies of performative verbs, the chapter then reviews historical studies of directive, commissive, and expressive speech acts in English. Directives in earlier English would seem to be more direct than we find today, but this can be attributed to the more fixed social structure, not to less politeness. Apologies, curses, greetings, and leave-takings represent expressives that have undergone change in the history of English, in respect to both their formal expression and their functional profile, that is, the very nature of the speech act itself. For example, promises of medieval times, which did not depend upon the sincerity condition of the speaker but were nevertheless “binding,” now rest fundamentally upon this condition.