"The past is a country we can never return to, but whose borders we are always crossing."

数学是给不同事物起相同名字的艺术。

The key ingredients of happiness could not be material or aesthetic, but must always stubbornly psychological.

每当我们提出问题的解决方案时，我们都应该尽力推翻我们的解决方案，而不是捍卫它。