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

Science makes no pretension to eternal truth or absolute truth.

Obvious is the most dangerous word in mathematics.

Nevertheless, the consuming hunger of the uncritical mind for what it imagines to be certainty or finality impels it to feast upon shadows in the prevailing famine of substance.

The only royal road to elementary geometry is ingenuity.

Any impatient student of mathematics or science or engineering who is irked by having algebraic symbolism thrust upon him should try to get along without it for a week.

I have always hated machinery, and the only machine I ever understood was a wheelbarrow, and that but imperfectly.