An inquiry into the problem of the relationship between language and thought as it is involved in general adult linguistic processing. The basic views are that language is a form of action, and that many utterances are constructed in terms of concrete models of reality (sensory-motor representations), which are linked to abstract conceptions through the process of semiotic extension. After a short review of previous work, M. presents his theory at length, and in a third section he adduces data from various perspectives to support it.