以下文字来自某个career talk，摘录在此供大家细细品位，句式简洁，但不乏深意，据说层次水平依次递增，当然一出生就level 4的不在我们的讨论之列，you know what i mean, right? :)
level 1: you know what you know
level 2: you don’t know what you don’t know
level 3: you know what you don’t know
level 4: you don’t know what you know
