过去从未死去，它甚至不是过去。

The right of a nation to kill a tyrant in case of necessity can never be doubted until the right of a tyrant to kill a nation has been proved.

Learning consists in the modification of certain mediating processes which operate between the stimulus and the response.

I'm not afraid of dying, I'm afraid of not trying.

城市是一个活生生的有机体，不断演变并适应其居民的需求。