  In 1628 Descartes left Paris. At this time he seems to have been working on the Regulae ad Directionem Ingenii (Rules for the Direction of the Mind), a work that he would abandon, some speculating around the time of the move from Paris. It is worth noting that relatively recently a copy of the Rules was discovered in a library at Cambridge University. Scholars are unsure how it got there. Currently, based on what it includes, it is thought that this manuscript represents the work as it stood when Descartes had abandoned it in 1628. The later Amsterdam printing (1701) and a copy that Leibniz acquired from Clerselier (c. 1670) make certain advancements over what is found in the Cambridge manuscript. So, it appears that Descartes picked up the work again. Some have speculated that this may have happened after a visit in 1635 from John Dury (1596–1680) and Samuel Hartlib (1600–1662), where Hartlib reports that Dury had returned to England with copies of some of Descartes’ works (Fallon, pp. 9f); the speculation being that the recently discovered manuscript is related to something brought back by Dury. The meeting took place in The Hague. Dury and Hartlib were friends of the Cambridge philosopher Henry More (1614–1687), with whom Descartes had corresponded, and of others in More’s circle, including John Milton (1608–1674). Perhaps the copy was made during the visit and brought back to Cambridge. (In any event, this is a new and interesting development in Descartes scholarship.) In 1630 Descartes moved to Amsterdam. There he worked on drafts of the Dioptrique (the Optics) and the Meteors (the Meteorology), which were very likely intended to be a part of a larger work, Le Monde (The World). In 1632 he moved again, this time to Deventer, to apparently teach Henry Reneri (1593–1639) his physics. It is also during his stay in Deventer that Descartes probably worked on a final draft of the Traite de l’homme (Treatise on Man), which in connection to the Optics and the Meteorology was probably originally intended to be a part of The World.