This Chapter deals with Descartes' struggle to redefine his projects and vocation, given the collapse of the Regulaein 1628. At this point he set out to become something we have not seen him intending to become at any previous moment, the author of a systematic, pro-Copernican and corpuscular-mechanical philosophy of nature, embodied first in Le Monde. We examine the events, episodes and tendencies which, some scholars have said, caused his move to systematic mechanism. In accord with the historiographical principles guiding this study, we eschew explanations by way of ruptures of agenda and identity, as well as explanations which assign sufficient causality to singular events and episodes. Taking a structured approach, we superimpose consideration of particular developments and events upon examination of fundamental intellectual commitments and agendas. This produces a dense description and explanation of what was a "process of inflection" of Descartes' projects, rather than a "crisis and break". The Chapter also includes a detailed reconstruction of the course of writing Le Monde,1629–1633.