Method, Groundwork, Foundation

At the outset of the Discourse, Descartes likens the development of a Method to the laying of a foundation of a building.  But, his metaphor betrays him.  For, as Kant recognizes, a foundation does not merely support a structure that is built upon it, it also rests upon some ground.  Thus, without adequate groundwork, the stability of the structure is threatened.  So, the Discourse is, more accurately, his groundwork, and the Meditations is his structure, from the foundation up.  Now, Descartes is in fact mindful, contrary to the subsequent glossing of him as a 'foundationalist' might suggest, that there exists a ground in need of work--the emergence of new Science that threatens traditional Theology.  So, the challenge for him is to develop a Method that is adequate to the task of working this ground.  But it is unclear if it is so adequate.  For, the Method consists in determining the believability of a proposition, whereas the problem is not one proposition or another, but the systemization of two sets of propositions.  Indeed, his apparent solution is to the problem of systemization, the cardinal element of which is not even established via his Method--the heart of his proposed solution is a systemizing proposition, 'God would not deceive me regarding Mathematics, i. e. thereby reconciling Theology and Science.  Furthermore, that proposition is not one that is ascertained via his Method, and, hence, is groundless--he takes it on faith.  Accordingly, the structure thereafter is, in terms of Descartes' own metaphor, a castle built on air, even if to that point the construction has been methodically sound.