Really? Not all your thoughts need to be voiced outside your brain.

Christian(Dec's brother) - Has anyone ever gotten stuck or fallen in a crack in any of these caves?
Tour guide - I'm not sure.  Not that I know of, but I don't know everything.
Declan - You know, you're right.
Tour guide - I am?  Thanks.
Declan - Yeah, you don't know everything.  No one can.

Luckily the tour guide was good natured and laughed with the rest of the group while I looked for a crack that I could fall into.