translation.en: We tend to infer the normal function of something by what doesn't happen when we take it away, by the opposite of what we see when we take it away.
translation.zh: 通过把某种因素剔除然后观察什么没有发生， 我们推断出这个被移除的因素的正常功能是什么。 也就是与我们看到正在发生的截然相反。