It is better to have no books at all than to believe in them all.

——Mencius

A scholar must first doubt.

——Cheng Yi (Northern Song Dynasty philosopher and educator)

Those who do not doubt when they are doubtful have never learned; learning requires doubt.

——Zhang Zai (Philosopher of the Northern Song Dynasty)

Those who have no doubts in reading must have doubts, and those who have doubts must have no doubts. Only here can they make progress.

——Zhu Xi

Senior scholars say that learning requires doubt. Small doubts lead to small progress, and great doubts lead to great progress. Doubts are the opportunity for enlightenment. A moment of enlightenment, a moment of progress.

——Chen Xianzhang (Ming Dynasty, thinker and calligrapher)