Well-observed facts, though brought to light by passing theories, will never die; they are the material on which alone the house of science will at last be built.

Mediocre men often have the most acquired knowledge. It is in the darker. It is in the darker regions of science that great men are recognized; they are marked by ideas which light up phenomena hitherto obscure and carry science forward.

Hatred is the most clear- sighted, next to genius.

Men who believe too firmly in their theories, do not believe enough in the theories of others. So ... these despisers of their fellows ... make experiments only to destroy a theory, instead of to seek the truth.

We must keep our freedom of mind, ... and must believe that in nature what is absurd, according to our theories, is not always impossible.

The investigator should have a robust faith - and yet not believe.

Put off your imagination, as you put off your overcoat, when you enter the laboratory. Put it on again, as you put on your overcoat, when you leave.