真相往往比虚构更不可思议。

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

War is an ugly thing， but not the ugliest of things； the decayed and degraded state of moral and patriotic feeling which thinks that nothing is worth war is much worse.

无论你正在经历什么，隧道的尽头总有一束光。