How can a certain line, or a certain surface, form an impassable barrier to space, or have any mobility different in kind from that of all other lines or surfaces? The notion cannot, in philosophy, be permitted for a moment, since it destroys that most fundamental of all the axioms, the homogeneity of space.

An Essay on the Foundations of Geometry, Chapter I, Section 45 (p. 49), Dover Publications, Inc. 1956