Mathematics is not about numbers, equations, computations, or algorithms: it is about understanding.
你记忆中的一切都不在了,还是忘掉比较好。
司马牛问君子。孔子说:“君子不忧不惧。”问:“不忧不惧,就能叫做君子吗?”孔子说:“问心无愧,何来忧惧?”
The purpose of abstraction is not to be vague, but to create a new semantic level in which one can be absolutely precise.