A clever person solves a problem. A wise person avoids it.

Man can find meaning in life, short and perilous as it is, only through devoting himself to society.

There are no arbitrary constants ... nature is so constituted that it is possible logically to lay down such strongly determined laws that within these laws only rationally determined constants occur (not constants, therefore, whose numerical value could be changed without destroying the theory).

I am ceaselessly occupied with the question of the constitution of radiation … This quantum question is so incredibly important and difficult that everyone should busy himself on it.

It is better to believe than to disbelieve; in doing you bring everything to the realm of possibility.

Science can flourish only in an atmosphere of free speech.

Don't do anything that goes against your conscience, even if your country says so.