The properties of one of the structures of politeness in the romance languages, the deference system connected with the use of conditional tenses, are analyzed in this paper. Although only Spanish examples are given, the conclusions also apply to French, Italian and Roumanian. The first part of the paper analyzes politeness in relation to its applicability to different illocutionary acts together with the types of sentences that may express them; the second part relates the conclusions of the first part to linguistic theory. Politeness is possible only in those speech acts in which greater control is assigned to the hearer than the speaker, and where the hearer must do something. Therefore, assertions, commands or acts of granting permission cannot be uttered in the polite form, whereas making suggestions or giving advice can be. Sentences with performative verbs or intonation contours and conditional markers fit easily into a linguistic formal theory of semantics. The case of conveyed illocutionary forces is more problematic. This form of politeness is contextual or pragmatic. This separation into two areas, however, seems artificial, since the rules that have been considered seem to function in a similar way and under similar conditions whether "semantic" or "pragmatic." (CFM)