I regard class differences as contrary to justice and, in the last resort, based on force.

Pure logical thinking cannot yield us any knowledge of the empirical world. All knowledge of reality starts from experience and ends in it.

Imagination is the highest form of research.

But science can only be created by those who are thoroughly imbued with the aspiration toward truth and understanding. This source of feeling, however, springs from the sphere of religion. To this there also belongs the faith in the possibility that the regulations valid for the world of existence are rational, that is, comprehensible to reason. I cannot conceive of a genuine scientist without that profound faith. The situation may be expressed by an image: science without religion is lame, religion without science is blind.

I cannot accept any concept of God based on the fear of life or the fear of death, or blind faith. I cannot prove to you that there is no personal God, but if I were to speak of him I would be a liar.

Give back to the world at least what you've received.

Work is the only thing that gives substance to life.