I don't know. I don't know is an answer you'd give to a question that seems worthless, something that you don't have an answer to. I don't know is something anyone would say when they're lost. I don't know is something anyone would say to a "how are you" question. But the real question is, what is "I don't know"? What does it actually mean? Do you know the answer? Does anyone know the answer?
Because I don't know, either.