The test of a first-rate intelligence is the ability to hold two opposed ideas in the mind at the same time, and still retain the ability to function.
测量一切可测之物，并把不可测的变为可测。
History is not the past. It is the present. We carry our history with us. We are our history.
A teacher must have a healthy body, the skills of a farmer, the mind of a scientist, the interest in art, and the spirit of social reform.
Never underestimate the importance of "useless" fundamental research.
