自然实验是理解现实世界中因果关系的强大工具。
Natural experiments are a powerful tool for understanding causal relationships in the real world.
应对不自由世界的唯一方法是变得如此绝对自由，以至于你的存在本身就是一种反抗。
The power of love is stronger than the power of force.
we can go back to the cave if you like.
Ninety-nine percent of the troubles that threaten our civilization come from too optimistic, therefore we should have a system where the accounting is a way more conservative.
Nothing can stop the man with the right mental attitude from achieving his goal; nothing on earth can help the man with the wrong mental attitude.