The one sentence summary

People don’t really know why they do what they do, nor how bad their decisions often are.


  • This is the extraordinary story of the friendship and working relationship between Daniel Kahneman and Amos Tversky, the founding fathers of Behavioural Economics. It is impossible to summarise in a conventional way, but it is full of fantastic insights. Pearls of wisdom include:


“I’ve always felt ideas were a dime a dozen. If you had one that didn’t work out, you should not fight too hard to save it, just go find another.”

“When someone says something, don’t ask yourself if it is true. Ask what it might be true of.”

“Because we tend to reward others when they do well and punish them when they do badly, and because there is regression to the mean, it is part of the human condition that we are statistically punished for rewarding others and rewarded for punishing them.”

“You don’t study memory. You study forgetting.”

“I get a sense of movement and discovery whenever I find a flaw in my thinking.”

“The way the creative process works is that first you say something, and later, sometimes years later, you understand what you said.”

“No one ever made a decision because of a number. They need a story.”


“The nice thing about things that are urgent is that if you wait long enough they aren’t urgent anymore.”

“When you are a pessimist and the bad thing happens, you live it twice. Once when you worry about it, and the second time when it happens.”

“Always keep one hand firmly on data.”

“Reality is a cloud of possibility, not a point.”


“Intuitive expectations are governed by a consistent misperception of the world.”

“It’s not just that people don’t know what they don’t know, but that they don’t bother to factor their ignorance into their judgments.”

“Unless you are kicking yourself once a month for throwing something away, you are not throwing enough away.”

“He who sees the past as surprise-free is bound to have a future full of surprises.”

“When people make decisions, they do not seek to maximise utility. They seek to minimise regret.”


“Most advances in science come not from eureka moments, but from ‘hmmm, that’s funny.’ ” Irv Biederman

“Last impressions can be lasting impressions.” Don Redelmeier


  • The title comes from some unfinished work towards the end of their career. The emotion of unrealised possibility is a product of two variables: the desirability and possibility of the alternative. Frustrated people need to undo some feature of their environment, and regretful people need to undo their own actions. Hence The Undoing Project.