All theory, dear friend, is gray, but the golden tree of life springs ever green.

Energy is the basis of everything. Every Jew, no matter how insignificant, is engaged in some decisive and immediate pursuit of a goal... It is the most perpetual people of the earth.

I examine my own being, and find there a world, but a world rather of imagination and dim desires, than of distinctness and living power. Then everything swims before my senses, and I smile and dream while pursuing my way through the world.

We can redeem anyone who strives unceasingly.

Art is long, life short, judgment difficult, opportunity transient. To act is easy, to think is hard; to act according to our thought is troublesome. Every beginning is cheerful: the threshold is the place of expectation.

I call architecture frozen music.

The close and thoughtful observer more and more learns to recognize his limitations. He realizes that with the steady growth of knowledge more and more new problems keep on emerging.