Guardian: The starting up of the hype machine for Donald Rumsfeld’s upcoming memoir has got me thinking about his famous line before the US invasion of Iraq. There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don’t know. But there are also unknown unknowns. There are things we don’t know we don’t know. In Rumsfeld’s case, the former Pentagon chief was basically admitting, albeit in an extremely …