Once a definition of congruence is given, the choice of geometry is no longer in our hands; rather, the geometry is now an empirical fact. - Hans Reichenbach

This fact... proves that space measurements are reducible to time measurements. Time is therefore logically prior to space.

...the mathematician uses an indirect definition of congruence, making use of the fact that the axiom of parallels together with an additional condition can replace the definition of congruence.

...the differential element of non-Euclidean spaces is Euclidean. This fact, however, is analogous to the relations between a straight line and a curve, and cannot lead to an epistemological priority of Euclidean geometry, in contrast to the views of certain authors.