Civilization advances by extending the number of important operations which we can perform without thinking about them. Operations of thought are cavalry charges in a battle - they are limited in number, they require fresh horses, and must only be made at decisive moments.

In every age of well-marked transition, there is the pattern of habitual dumb practice and emotion which is passing and there is oncoming a new complex of habit.

The study of mathematics is apt to commence in disappointment.

Problems are only opportunities in disquise.

Each human being is a more complex structure than any social system to which he belongs.

In formal logic, a contradiction is the signal of defeat, but in the evolution of real knowledge it marks the first step in progress toward a victory.

Everything of importance has been said before by somebody who did not discover it.