老年人相信每一件事物；中年人猜疑每一件事物；青年人什么都懂。

Mathematics is not a deductive science—that's a cliché. When you try to prove a theorem, you don't just list the hypotheses and then start to reason. What you do is trial and error, experimentation, guesswork.

历史不是关于陌生人的故事，不是来自另一个世界的异类；它是关于如果早出生一点的我们的故事。