老年人相信每一件事物;中年人猜疑每一件事物;青年人什么都懂。
A mathematician's work is never done; there are always new questions to explore and new mysteries to uncover.
La verdadera patria del hombre es su infancia.
解释:向外物游览就要要求外物的完备,向自己内心求取,则能充实完善自身。