Practical application is found by not looking for it, and one can say that the whole progress of civilization rests on that principle.
Quoted in H Eves Mathematical Circles Squared (Boston 1972).
To parents who despair because their children are unable to master the first problems in arithmetic I can dedicate my examples. For, in arithmetic, until the seventh grade I was last or nearly last.
Quoted in D MacHale, Comic Sections (Dublin 1993)
Logic merely sanctions the conquests of the intuition.
Quoted in M Kline, Mathematical thought from ancient to modern times (New York, 1972).
Can the existence of a mathematical entity be proved without defining it ?