"It is remarkable that this generalization of plane geometry to surface geometry is identical with that generalization…"

"If heat were the affecting force, direct indications of its presence could be found which would not make use of geome…"

"Although it is admitted that certain differences cannot be verified by experiment, we should not infer from this fact…"

"The surfaces of three-dimensional space are distinguished from each other not only by their curvature but also by cer…"

"...the stereographic projection of the spherical surface. From the north pole P we draw radial lines to project every…"

"...the order of betweenness does not depend on mutual distances... betweenness is purely a relational order."

"...the relation of betweenness on the torus is undetermined for curves that cannot be contracted to a point [e.g., ci…"

"Euclidean geometry can be easily visualized; this is the argument adduced for the unique position of Euclidean geomet…"

"Visual forms are not perceived differently from colors or brightness. They are sense qualities, and the visual charac…"

"If along the path of truth, success (which was often near-failure unnoticed) is subjected to the same scrutiny and de…"