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.

When entering on new ground we must not be afraid to express even risky ideas so as to stimulate research in all directions. As Priestley put it, we must not remain inactive through false modesty based on fear of being mistaken.

The first requirement in using statistics is that the facts treated shall be reduced to comparable units.

Science increases our power in proportion as it lowers our pride.

First causes are outside the realm of science.

A great discovery is a fact whose appearance in science gives rise to shining ideas, whose light dispels many obscurities and shows us new paths.

But while I accept specialization in the practice, I reject it utterly in the theory of science.