Halliday (2008: 125):
Language has an almost unlimited capacity for construing our experience of reality — not surprising, because that is one of the two major functions, or “metafunctions”, in which it evolved. It sets up a virtual universe of meaning as interface between ourselves and the external world. The other major function was that of enacting our social identities, managing the complex interpersonal and institutional relationships within which human beings, and human cultures, have evolved.