Natural experiments are a powerful tool for understanding causal relationships in the real world.

I don’t regret the things I’ve done, I regret the things I didn’t do when I had the chance.

赏析：强调了孝子和忠臣应该以真诚和正直的态度对待父母和君主，而不是阿谀奉承。

故事的力量在于它可以改变世界。