Natural experiments are a powerful tool for understanding causal relationships in the real world.
I have made a ceaseless effort not to ridicule， not to bewail， not to scorn human actions， but to understand them.
To think is to confine yourself to a single thought that one day stands still like a star in the world's sky.
最有力的艺术往往是最模糊的。
The greatest killer of happiness is comparison. If you must compare， compare yourself to you yesterday