Geocentrism, Heliocentrism, Dualism

The Theological urgency for Descartes are the consequences of replacing Geocentrism with Heliocentrism.  Entailed in the replacement is the displacement of his deity in the former by the latter.  In Geocentrism, that deity inhabits the celestial realm that surrounds the Earth, and that, hence, is physically contiguous with it.  Accordingly, in Heliocentrism, that deity has no astronomical location, and no potential causal connection with the Earth.  Immaterial-Material Dualism solves that problem, by relocating his deity in the latter realm, with the power of crossing the divide.  Hence, to anchor that Theological revision with an I Exist that is the true premise of the traditional proofs of the existence of that deity, Descartes needs to instantiate the Dualism within the I Exist.  Thus, a primary Theological goal of his thought experiment is to separate Thinking from the Corporeal realm, and to attribute to the I Exist that it is essentially a Thinking being.  So, his Dualism, and the Epistemological implications of that, are extrinsic to Descartes' project of otherwise methodically incorporating Heliocentrism into his system.