 Within physics the idealist currents lying behind the world geometries of Weyl and Eddington were largely ignored, whereas within philosophy, with the notable exception of Émile Meyerson’s La Déduction Relativiste (1925). Meyerson, who had no doubt concerning the basic realist impetus of science, carefully distinguished Einstein’s “rational deduction of the physical world” from the speculative geometrical unifications of gravitation and electromagnetism of Weyl and Eddington. These theories, as affirmations of a complete panmathematicism, or rather of a pangeometrism (1925: §§ 157–58), were compared to the rationalist deductions of Hegel’s Logic. That general relativity succeeded in partly realizing Descartes’ program of reducing the physical to the spatial through geometric deduction, is due to the fact that Einstein “followed in the footsteps” of Descartes, not Hegel (1925: §133). But pan-geometrism is also capable of overreaching itself and this is the transgression committed by both Weyl and Eddington. Weyl in particular is singled out for criticism for seemingly to have reverted to Hegel’s monistic idealism, and so to be subject to its fatal flaw. In regarding nature as completely intelligible, Weyl had abolished the thing-in-itself and so promoted the identity of self and non-self, the great error of the Naturphilosophien.