about 95% of the experiments we do are total failures, and that’s because we’re out there on the leading edge of what’s possible, and most of the time it isn’t quite possible.

And some of the things that we saw in the ’80s, really, they were failures, because patients died. But they allowed us to diagnose the systems’ problems and say, “This is where we need a community health worker system. This is where we need to make sure patients have food support while they’re getting these medicines,” et cetera. So those are examples of tragedies that certainly lead to — not just personal epiphanies — but collective epiphanies, where you say, “You know what? We can do this better if we have the system fixed.”

Unfortunately, in the case of Iraq, I believe we could have done that through an inspection process. I was calling for a few months more to complete our work. We hadn’t seen indications of weapons of mass destruction. We hadn’t seen indications of nuclear weapons. ... Unfortunately, it didn’t work that way. There was faulty intelligence. There were lots of other considerations that made a decision to go to war tempting, to get rid of Saddam Hussein.

So Cambridge rejected me. Quite rightly, although at the time I thought it was a little churlish. So, I had to do it without any university training. ... and I began to realize that there were probably a lot more of these things, and that if you find these things, you get a position in the ladder which you can’t get to unless you have either got an education or something else. So by finding important things, you immediately get into the game, which you’d been excluded from otherwise.

Amos and I shared the wonder of together owning a goose that could lay golden eggs – a joint mind that was better than our separate minds. … Some of the greatest joys of our collaboration-and probably much of its success – came from our ability to elaborate each other's nascent thoughts: if I expressed a half-formed idea, I knew that Amos would be there to understand it, probably more clearly than I did, and that if it had merit he would see it. Like most people, I am somewhat cautious about exposing tentative thoughts to others – I must first make sure that they are not idiotic. In the best years of the collaboration, this caution was completely absent.

Under the stress of the event, we felt, the soldiers' true nature would reveal itself, and we would be able to tell who would be a good leader and who would not. But the trouble was that, in fact, we could not tell. Every month or so we had a "statistics day," during which we would get feedback from the officer-training school, indicating the accuracy of our ratings of candidates' potential. The story was always the same: our ability to predict performance at the school was negligible. But the next day, there would be another batch of candidates to be taken to the obstacle field, where we would face them with the wall and see their true natures revealed. I was so impressed by the complete lack of connection between the statistical information and the compelling experience of insight that I coined a term for it: "the illusion of validity."