Solitude is painful when one is young, but delightful when one is more mature.

The human spirit must prevail over technology.

This has been done elegantly by Minkowski; but chalk is cheaper than grey matter, and we will do it as it comes.

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

Not until we dare to regard ourselves as a nation, not until we respect ourselves, can we gain the esteem of others, or rather only then will it come of its own accord

[O]nly if every individual strives for truth can humanity attain a happier future; the atavisms in each of us that stand in the way of a friendlier destiny can only thus be rendered ineffective.

Everybody felt his superiority, but nobody felt oppressed by it. Though he had no illusions about people and human affairs, he was full of kindness toward everybody and everything. Never did he give the impression of domineering, always of serving and helping. He was extremely conscientious, without allowing anything to assume undue importance; a subtle humor guarded him, which was reflected in his eyes and in his smile.