"The more we learn about life, the more we realize how much we have yet to discover."
以物易物、互通有无的倾向是人类共有的,也是其他动物所没有的。
学习数学的唯一方法就是做数学。
Profit is not the legitimate purpose of business. The legitimate purpose of business is to provide a product or service that people need and do it so well that it's profitable.