In order to examine the influences that brought Descartes to develop the theory of perception presented in the former chapter, we should return to his earliest work that has survived and contains a theory of perception, the Rules for the Direction of the Mind (Regulae ad Directionem Ingenii). Descartes worked on the Rules, perhaps intermittently, while in Paris in the mid-sixteen-twenties, and stopped his work when he moved to the Netherlands in late 1628, leaving the book unfinished. The book, written in Latin, was first published in a Dutch translation in 1684, and later in its original Latin in 1701. A copy of the original, containing several variants on the 1701 edition, was bought by Leibniz in Amsterdam in 1670 and is still extant. The original manuscript was, however, lost.¹