Everyone agrees on two things: that a majority of people are stupid, and that they are not one of them. We can as such deduce that a common factor shared among all stupid people is a sincere belief that they are not stupid. I can say I’m smart, but that’s exactly what a stupid person would say. Therefore the only way to prove objectively that I am smart is to believe I am stupid, which is the one thing a stupid person would never do. Unfortunately reaching this conclusion makes me feel smart, which reintroduces the possibility that I may be stupid. I realize now that my only choice it to believe that I may or may not be stupid, and I don’t feel any way about that.
Solved, next question.