We return, now, from this necessary digression, to follow onward our leading inquiry, "Why we speak as we do?" And we have to push the question a step further than in the last lecture, asking this time, not simply how we ourselves came into possession of the signs of which our mother-tongue is made up, but also how those from whom we learned them came into possession of them before us; how the tradition from whose hands we implicitly accepted them got them in the form in which it passed them on to us; why our words, in short, are what they are, and not otherwise. We have seen that every part and particle of every existing language is a historical product, the final result of a series of changes, working themselves out in time, under the pressure of circumstances, and by the guidance of motives, which are not beyond the reach of our discovery. This fact prescribes the mode in which language is to be fruitfully studied. If we would understand anything which has become what it is, a knowledge of its present constitution is not enough: we must follow it backward from stage to stage, tracing out the phases it has assumed, and the causes which have determined the transition of one into the other. Merely to classify, arrange, and set forth in order the phenomena of a spoken tongue, its significant material, usages and modes of expression, is grammar and lexicography, not linguistic science. The former state and prescribe only; the latter seeks to explain. And when the explanation is historical, the search for it must be of the same character. To construct, then, by historical processes, with the aid of all the historical evidences within his reach, the history of development of language, back to its very beginning, is the main task of the linguistic student; it is the means by which he arrives at a true comprehension of language, in its own nature and in its relations to the human mind and to human history.
Furthermore, it is hardly necessary to point out that the history of language reposes on that of words. Language is made up of signs for thought, which, though in one sense parts of a whole, are in another and more essential sense isolated and independent entities. Each is produced for its
