Real experts have no trouble saying: “I don’t know.”
They’ve got a clear sense of how far their expertise extends, and where it ends. They never, ever want to mislead you. Therefore, real experts will be the first to admit when the question you’ve just asked exceeds their personal knowledge. If they’re really good, they’re likely to introduce you to someone who does have a good answer for you. Remember your days in grade school, and the embarrassment a student felt when he or she had to admit to the teacher, ‘I don’t know?’ Real experts have overcome that reluctance.