勇气不是没有恐惧，而是战胜恐惧。

States are inherently aggressive and expansionist because they exist in an anarchic international system where there is no higher authority to keep them in check.

数学的美在于它的简洁性和普遍性。

Sustainability isn't an option; it's a responsibility we owe to future generations.

一个人对自己的态度是过上长寿且相对幸福生活的最重要因素。