Don't let your brain interfere with your heart.

Only one who devotes himself to a cause with his whole strength and soul can be a true master. For this reason mastery demands all of a person.

The value of a man should be seen in what he gives and not in what he is able to receive.

What distinguishes the language of science from language as we ordinarily understand the word? ... What science strives for is an utmost acuteness and clarity of concepts as regards their mutual relation and their correspondence to sensory data.

I am enough of an artist to draw freely upon my imagination.

Empathy is patiently and sincerely seeing the world through the other person's eyes. It is not learned in school; it is cultivated over a lifetime.

Berlin is the place to which I am most closely bound by human and scientific ties.