The highest possible stage in moral culture is when we recognize that we ought to control our thoughts.  
 道德修养的最高境界,是认识到我们必须控制自己的思想。
Every tree planted today is a promise to tomorrow.
Give the pupils something to do, not something to learn; and the doing is of such a nature as to demand thinking; learning naturally results.
这只是海森堡测不准原理的简单应用而已。
如果一个聪明人干了一件蠢事,那就不会是一件小小的蠢事。