 Especially where Kepler deals with the geometrical structure of the cosmos, he always returns to his Platonic and Neoplatonic framework of thought. Thus, the polyhedral hypothesis (see Section 3 below) he postulated for the first time in his MC represents a kind of “formal cause” constituting the foundational structure of the universe. In addition, an “efficient cause,” which realizes this structure in the corporeal world, is also needed. This is, of course, God the Creator, who accomplished His work according to the model of the five regular polyhedra. Kepler reinterprets the traditional statements about the Creation as an image of the Creator giving to the ancient ideas a more systematic and a quantitative character. Even the doctrine of the Trinity could be geometrically represented, taking the center for the Father, the spherical surface for the Son, and the intermediate space, which is mathematically expressed in the regularity of the relationship between the point and the surface, for the Holy Spirit. In Kepler’s model, we have to be able to reduce all appearances to straightness and curvature as providing the foundation for the geometrical structure of the world’s creation. The very first category, through which God produced a fundamental similitude of the created World to Himself, is that of quantity (see MC, chapter 2, KGW pp. 23–26). Furthermore, quantity was also introduced into the human soul for the specific purpose that this fundamental symmetry could be apprehended and known scientifically.