 One might wonder why, though, there have historically been virtually no revisions of mathematics on empirical grounds. A common example offered is how Riemannian replaced Euclidean geometry in Einstein’s theory of General Relativity. But this mis-interprets the history. Non-Euclidean geometries were purely conceptual developments in the 19th C. by mathematicians such as Gauss, Riemann and Lobechevsky. Einstein simply argued in 1916 that one of these conceptual possibilities seemed to be better supported by physics than was the traditional Euclidean one, and should therefore be taken to be true of actual space(-time). It is only this latter claim that is empirical.