 For a thorough discussion of the anti-Kantian implications of “On the Origin and Significance of the Axioms of Geometry,” see DiSalle 1993, 516ff. DiSalle discusses Helmholtz’s famous debate with the Kantian J. P. N. Land, as does David Hyder (Hyder 2006, Land 1877). DiSalle also mentions that in 1972, Jürgen Ehlers, Felix Pirani, and Alfred Schild “derived the metric of general-relativistic spacetime from assumptions about falling bodies and light rays” (DiSalle 1993, 520n). Ehlers, Pirani, and Schild note that their method “has some similarity to Helmholtz’s derivation of the metrics of spaces of constant curvature” (Ehlers et al. 1972, 65). 