Well, Socrates' knowing that he knew nothing was counted a real insight! Uh, and his singular wisdom was proclaimed by a psychedelic-inhaling priestess in a temple, no less.

It didn't work for me though—in epistemology class once I said to the lecturer "I don't know anything!"—not being flippant, at the time I really felt I couldn't be 100% certain of anything—and he said instantly, unimpressed, "Don't you know your name?".. (Which didn't seem quite fair. He didn't "respond to the strongest plausible interpretation". Or maybe he did.)