[...] For the child language is very much a part of himself, and the ʻpersonalʼ model is his intuitive awareness of this, and of the way in which his individuality is identified and realized through language. The other side of the coin, in this process, is the child’s growing understanding of his environment, since the environment is, first of all, the ʻnon-selfʼ, that which is separated out in the course of establishing where he himself begins and ends. So, fifthly, the child has HEURISTIC model of language, derived from his knowledge of how language has enabled him to explore his environment. The heuristic model refers to language as a means of investigating reality, a way of learning about things.
- Halliday (1973), a pag.14