True leadership is about serving others, not yourself.

Freedom is not merely the opportunity to do as one pleases; neither is it merely the opportunity to choose between set alternatives. Freedom is, first of all, the chance to formulate the available choices, to argue over them - and then, the opportunity to choose.

The world is made of words, and those words are so powerful that they can create worlds.

The spread of liberal democracy around the world is not inevitable, but it is the most likely outcome given the alternatives.

Sustainability isn't an option; it's our responsibility to future generations.

宇宙是一个庞大而复杂的系统，理解它需要理论洞察力和观测证据。