The most important thing in learning is doubt. A small doubt will lead to small progress, and a big doubt will lead to great progress. Doubt is the foundation of enlightenment.

Translation:

The key to learning is to be good at thinking and have doubts. If you have small questions and confusions (and think about them), you will make small progress; if you have big questions If you have questions and confusions (and think about them), you will make great progress. Doubt is the basis for awakening and understanding.