The state, therefore, has not existed from all eternity. There have been societies that did without it, that had no notion of the state or state power. At a certain stage of economic development, which was necessarily bound up with the split of society into classes, the state became a necessity.

大自然是最好的老师；它已经做了实验，我们只需要解读它们。

街道因比夜晚更黑暗的东西而黑暗。

一个好计划的最大敌人是梦想一个完美的计划。坚持好的计划。

The key to credible causal inference is not just the method, but how well the method fits the question at hand.

The discovery of gravitational waves was a testament to the power of human ingenuity and perseverance.