Animals, we have been told, are taught by their organs. Yes, I would add, and so are men, but men have this further advantage that they can also teach their organs in return.

The aim of living is life itself.

It is easier to perceive error than to find truth, for the former lies on the surface and is easily seen, while the latter lies in the depth, where few are willing to search for it.

One cannot always be a hero, but one can always be a man.

Everything factual is, in a sense, theory. The blue of the sky exhibits the basic laws of chromatics. There is no sense in looking for something behind phenomena: they are theory.

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.

Time itself is an element.