分隔生与死的界限至多是模糊不清的。谁能说一个在哪里结束，另一个在哪里开始？
The boundaries which divide Life from Death are at best shadowy and vague. Who shall say where the one ends, and where the other begins?
You cannot make yourself feel something you do not feel, but you can make yourself do right in spite of your feelings.
We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time.
学习数学的唯一方法就是做数学。