Yes, Prime Minister (The Grand Design)

Jim: It's a bluff, I probably wouldn't use it (the nuclear missile).
Sir Humphrey: Yes but they don't know that you probably wouldn't.
Jim: They probably do.
Sir Humphrey: Yes, they probably know you probably wouldn't but they can't be certain.
Jim: They probably, certainly know that I probably wouldn't.
Sir Humphrey: Yes, but even though they're probably certain you know you probably wouldn't they don't certainly know that although you probably wouldn't, there is no probability that you certainly would.
Jim: What?

- The Grand Design