You don't have to be perfect to be a good baker.

To kill an error is as good a service as, and sometimes even better than, the establishing of a new truth or fact.  

知识最大的敌人不是无知，而是知识的幻觉。

译文：学习、询问、思考、辨析、实践，都是做学问的方法，没有只学习而不实践的。