解释：人有知识，犹如树木有枝叶，树木有了枝叶，能带给人阴凉，人有了知识，就可以为人民做更多的事。

The individual's biography is shaped by the historical and social context in which it is embedded.

I must study politics and war that my sons may have liberty to study mathematics and philosophy.

Let’s face it, a nice creamy chocolate cake does a lot for a lot of people; it does for me.　　

世界上最好和最美丽的东西是看不见甚至摸不着的——它们必须用心去感受。