De vulgari eloquentia (I, i, 3-4)

(3) Est et inde alia locutio secondaria nobis, quam Romani gramaticam vocaverunt. Hanc quidem secundariam Greci habent et alii, sed non omnes. Ad habitum vero huius pauci perveniunt, quia non nisi per spatium temporis et studii assiduitatem regulamur et doctrinamur in illa. (3) There also exists another kind of language, at one remove from us, which the Romans called gramatica [grammar]. The Greeks and some - but not all - other peoples also have this secondary kind of language. Few, however, achieve complete fluency in it, since knowledge of its rules and theory can only be developed through dedication to a lengthy course of study
(4) Harum quoque duarum nobilior est vulgaris: tum quia prima fuit humano generi usitata; tum quia totus orbis ipsa perfruitur, licet in diversas prolationes et vocabula sit divisa; tum quia naturalis est nobis, cum illa potius artificialis existat. Et de hac nobiliori nostra est intentio pertractare. (4) Of these two kinds of language, the more noble is the vernacular: first, because it was the language originally used by the human race; second, because the whole world employs it, though with different pronunciations and using different words; and third because it is natural to us, while the other is, in contrast, artificial. And this more noble kind of language is what I intend to discuss.