We speak because we live in society: this might seem a truism, the statement of which scarcely needs any lengthy justification; all those involved in the study of social groups, under whatever aspect, know that the knowledge of language is one of the conditions at the basis of their research and one of the essential means at their disposal for successfully carrying out their task, delving more deeply into the facts, and verifying their results. It would seem that those linguists who do not conceive of language as an interpretation, but rather as the pure subject material of their science, also have to express their agreement with regard to the evidence of the proposition; in fact, if the sociological character of the linguistic fact has never been denied, the attention which has been devoted to it has varied considerably.