Great doubt, great understanding (大疑大悟)

This is perhaps the most popular version of Great doubt in 21st century China

Fuller quote as seen e.g. at: www.hrfjw.com/fjrw/hcrw/ywfs/324750.html

大疑大悟，小疑小悟，不疑不悟

translation;

Great doubt, great underestanding. Small doubt, small understanding. No doubt, no understanding.

k.sina.cn/article_5668613235_151e02c7300100wutq.html attributes it to modern day Chinese "Master Chongci" (崇慈法师).