The fame of Abraham Vander-Mylius (Abraham van der Myl, 1563-1637) as a linguist persisted through many generations. The Lingua Belgica of the Dutch theologian, which appeared at Leiden in 1612, had a clarity, freshness, and persuasiveness which were vital factors in establishing its reputation. Even today, the work has value as revealing, both explicitly and implicitly, views on language that were current in the author's time. This article is particularly concerned with the attitude which Mylius displayed toward the historical, diachronic aspects of language. The primary aim is to present as clearly as possible Mylius' own views on this phase of language; only incidentally are we concerned with his sources.