自由不是恩赐，而是必须争取的权利。

教育是对人力资本的投资，会以更高生产率的形式获得回报。

We must be long-termists and not be tempted by short-term interests.

The great secret that all old people share is that you really haven't changed in seventy or eighty years. Your body changes, but you don't change at all. And that, of course, causes great confusion.

要解决问题，你必须愿意以不同的方式思考。

我唯一能依靠的就是我自己的不确定性。

Coal is not just a commodity, it's a commitment to America's future.