My experience working on a Ph.D. in mathematics was that the people who say, "I don't know." without any embarrassment are the smart people. They are the ones who know their stuff. My experiences since graduate have enforced this belief of mine.
Smart people are more aware of the things they don't know. They are not ashamed of saying so. There are exceptions of course but generally I've found this to be true.
Smart people are more aware of the things they don't know. They are not ashamed of saying so. There are exceptions of course but generally I've found this to be true.