The universe would look to a two-dimensional creature who spend its life moving on the service of what turned out to be a globe， it could travel for millions of years and would always return to its starting point， it would never be conscious of what was above it or beneath it.

"Randomized experiments are the gold standard for causal inference, but they are not always feasible."

【解释】在狭窄的路上行走，留一点余地让别人走；遇到美味可口的食物，留出三分让给别人吃，这是立身处世最快乐的方法。

当一种编程语言的程序需要关注无关的细节时，它就是低级的。