道的法则本是无为而自然，似有似无，玄妙难测。
孔子说：“生来就知道的，是上等人；学习后才知道的，是二等人；遇到困难才学习的，是三等人；遇到困难也不学习的，这就是下等人了。”
What is freedom of expression? Without the freedom to offend, it ceases to exist.
心理学不仅要描述意识的事实，还要解释它们。
I don't think that everyone should become a mathematician, but I do believe that many students don't give mathematics a real chance.