In this world, there is no lack of people who are ashamed of saying “I don’t know”, as they are afraid of being deemed as ignorant and ill-informed nuts. We're now in an era of information, and people are constantly filling their brains with various "knowledge"  so as to keep pace with the times. 

Once being asked a question in public, they don't want to say "I don't know" even that they really have liitle idea about it. But for me, I am especially in favor of a sentence said by Confucius, that is, “知之为知之 不知为不知 是知也”, which means “It is wise to hold what you know and admit what you don't know” or “Wisdom lies in admitting what you know as well as what you don't know”.