To understand mathematics is to understand the fabric of reality.
工具变量的美妙之处在于它们让我们以新的视角看世界。
The most considerable difference I can see between men and animals is not in reason, but in the extent of the power of using it.
富人的舒适依赖于穷人的大量供应。
He who is not contented with what he has,would not be contented with what he would like to have.