Even stranger things have happened; and perhaps the strangest of all is the marvel that mathematics should be possible to a race akin to the apes.

Poincaré [was] the last man to take practically all mathematics, pure and applied, as his province. ... Few mathematicians have had the breadth of philosophic vision that Poincaré had, and none in his superior in the gift of clear exposition.

Science makes no pretension to eternal truth or absolute truth.

The longer mathematics lives the more abstract - and therefore, possibly also the more practical - it becomes.

Euclid taught me that without assumptions there is no proof. Therefore, in any argument, examine the assumptions.

The only royal road to elementary geometry is ingenuity.

Wherever groups disclosed themselves, or could be introduced, simplicity crystallized out of comparative chaos.