One of the central claims put forward in the language-based theory of learning proposed by both Vygotsky and Halliday is that the very same conversations that provide the opportunity for the child to learn language also provide the opportunity to learn through language. That is to say, by participating in the conversations that form part of most everyday activities, the child not only appropriates the culture's chief means of interpersonal communication, but also its ways of making sense of experience, as these are encoded in the discourse contributions of the coparticipants in those activities. As Halliday puts it: “language is the essential condition of knowing, the process by which experience becomes knowledge” (1993a, p. 94).

This is a strong claim and one that is clearly relevant to the ongoing educational debate about “educational knowledge” – what should be taught and how. However, what is surprising about this debate is how little attention is given to the nature of the knowledge over which there is so much disagreement. What does it mean to talk about either the “transmission” or the “transformation” of knowledge, and how are these processes achieved in the discourse, both spoken and written, which constitute the major forms of activity in classrooms at all levels from kindergarten to university. In this and the next chapter I want to explore these issues in farther detail.

As I shall argue below, knowledge construction and theory development most frequently occur in the context of a problem of some significance and take the form of a dialogue in which solutions are proposed and responded to with additions and extensions or objections and counterproposals from others.