I live in that solitude which is painful in youth, but delicious in the years of maturity.

Nothing truly valuable can be achieved except by the unselfish cooperation of many individuals.

The really valuable method of thought to arrive at a logically coherent system is intuition.

It is the theory which decides what we can observe

Belief in an external world independent of the perceiving subject is the basis of all natural science.

What good is a reputation not put to good use.

In two weeks the sheeplike masses of any country can be worked up by the newspapers into such a state of excited fury that men are prepared to put on uniforms and kill and be killed, for the sake of the sordid ends of a few interested parties. Compulsory military service seems to me the most disgraceful symptom of that deficiency in personal dignity from which civilized mankind is suffering today.