"There are known knowns. There are things we know we know. We also know there are known unknowns. That is to say, we know there are some things we do not know. But there are also unknown unknowns, the ones we don't know we don't know."

....from a February 12, 2002 news briefing.

I think we can get an infinite regression out of this:

What about the unknown unknown unknowns? Those are the ones we don't know we don't know we don't know.

nah...!
The very first 'unknown' covers all the subsequent ones, but it is possible to dream that you are dreaming.

"There is bull sh*t, that is, there is sh*t that we know is a bulls. Then there is just plain sh*t, we really don't know where that sh*t comes from, but if I put your face in it, then we'd know something about that sh*t."

-Donald Rumsfeld

...from a memo discussing foreign policy.

I've dreamed I'm awake. But I was only dreaming. Then I really woke up.

I dreamed I was dreaming that I couldn't wake up. It's OK, I was just dead. Phew!