"I believe what I said yesterday. I don't know what I said, but I know what I think... and I assume it's what I said."
"We do know of certain knowledge that he (Osama Bin Laden) is either in Afghanistan, or in some other country, or dead."
"I would not say that the future is necessarily less predictable than the past - I think the past was not predictable when it started."and of course...
"Reports that say that something hasn't happened are always interesting to me, because as we know, 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."