In Chapter 3, while discussing the ways in which language use was necessarily socially situated, I commented that writings are interventions in a continuing communicative process and are intended to have an effect within that process. In this respect they are rather like conversations, though with three significant differences. The first is that they are, in a sense, only one side of the conversation, and therefore have to imagine (or construct) an ideal addressee; the second is that they are planned but, in their finished state, show little evidence of their planning in the form of crossings out, etc.; and the third is that the texts themselves remain as a kind of residue after they have fulfilled their function, whereas in conversation what has been said (as text) has to all intents and purposes been lost after it has been spoken. These three features have a significant effect on the ways in which we view writings, and are influential in shaping the process of production. But the first two are crucial to our understanding of language variation since identifying appropriate readers and offering them coherent messages necessarily involves differentiating readers and messages and this can only be done by constructing texts in different ways.