The world is the totality of facts, not of things.
When you are young, you think that the world is a place where you can live as you choose. But as you get older, you realize that the world is a place where you have to live as you must.
数学的美在于它能够以最抽象的术语描述宇宙。
【译文】将知识默记在心，学习时，不感到满足，教人时，不感到倦怠，这三方面我做到了哪些呢？