God always takes the simplest way.

Most people go on living their everyday life: half-frightened, half indifferent, they behold the ghostly tragic-comedy that is being performed on the international stage before the eyes and ears of the world.

The only source of knowledge is experience.

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.

People are like bicycles. They can keep their balance only as long as they keep moving.

Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world.

My mind is my laboratory.