Kahneman knows how interesting all of this is. What he doesn’t seem to notice is the natural question that springs into the mind of the lay reader: Who rigs up a wheel of fortune to show how people can be deceived by a number? How does that occur to anyone to do? And why? There’s a quality both impish and joyous to Kahneman’s work, and it is most on display in his collaboration with Amos Tversky. They had a rule of thumb, he explains: they would study no specific example of human idiocy or irrationality unless they first detected it in themselves. “People thought we were studying stupidity,” says Kahneman. “But we were not. We were studying ourselves.” Kahneman has a phrase to describe what they did: “Ironic research.”Kahneman has always insisted that the ideas for which he’s best known, along with his Nobel Prize in Economics, are not his but theirs. Once upon a time he collided almost by accident with another curious person, Amos Tversky, and the collision wound up defining them both.At some point in my conversations with Kahneman I wanted to know more about his other half. My former student Oren Tversky put me in touch with his mother, Barbara, who put me onto the papers left behind by her husband. As I paged through these a pattern presented itself to my mind. Perhaps I was just seeing what my mind expected to see, but it seemed to me that anyone who had become deeply aware that our species often did not make a lot of sense eventually found their way to Kahneman and Tversky.Then one afternoon I came upon a letter dated June 4, 1985, from Bill James. The baseball analyst whose work was then being blithely ignored by professional baseball people had wanted help answering a question that vexed him: Why were baseball professionals forever attempting to explain essentially random and therefore inexplicable events? “Baseball men, living from day to day in the clutch of carefully metered chance occurrences, have developed an entire bestiary of imagined causes to tie together and thus make sense of patterns that are in truth entirely accidental,” James wrote. “They have an entire vocabulary of completely imaginary concepts used to tie together chance groupings. It includes ‘momentum,’ ‘confidence,’ ‘seeing the ball well,’ ‘slumps,’ ‘guts,’ ‘clutch ability,’ being ‘hot’ and ‘cold,’ ‘not being aggressive’ and my all time favorite the ‘intangibles.’ By such concepts, the baseball man gains a feeling of control over a universe that swings him up and down and tosses him from side to side like a yoyo in a high wind.” It wasn’t just baseball he was writing about, James continued. “I think that the randomness of fate applies to all of us as much as baseball men, though it might be exacerbated by the orderliness of their successes and failures.”Bill James was clearly roubled that the human mind settled so easily on false explanations when the truth was readily at hand. He wondered if students of the human mind might help him to explain why.What Daniel Kahneman now swears is the last book he will ever write does exactly this. But in a funny way it is not his book. It’s theirs.