数学的本质在于它的自由。
The essence of mathematics lies in its freedom.
A poet is a nightingale, who sits in darkness and sings to cheer its own solitude with sweet sounds.
诗人是一只夜莺，坐在黑暗中用甜美的声音歌唱来鼓舞自己的孤独。
Natural experiments are a powerful tool for understanding causal relationships in the real world.
Start by doing what's necessary; then do what's possible; and suddenly you are doing the impossible.
从做必要的事情开始；然后做可能的事情；突然间你就在做不可能的事情了。
The knowledge of the circumstances of which we must make use never exists in concentrated or integrated form, but solely as the dispersed bits of incomplete and frequently contradictory knowledge which all the separate individuals possess.
今天我们种下的每一粒种子都是对后代的承诺。
我们活着就是为了改变世界，否则还有什么意义？
勤奋战胜贫穷，谨慎避免祸患，小心防止侵害，警惕免遭灾难。点评：《易经》曾言「君子终日乾乾，夕惕若。厉，无咎。」君子不仅整日自强不息、勤奋谨慎，而且到了晚上也心存警惕。如此这般，才能免除灾祸，事业得以顺利发展。