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By Root 1071 0

“What we need now is a return to common sense!” It’s an appealing notion, and drew loud applause at the time, but I couldn’t help wondering what it was that he meant by it. After all, two years earlier at the 2007 Davos meeting, much the same mix of businesspeople, politicians, and economists were congratulating one another on having generated astonishing levels of wealth and unprecedented stability of the financial sector. Did anyone suspect that they had somehow taken leave of their common sense? And if not, then how exactly would it help to return to it? If anything, in fact, what the history of financial crises, both before and after the advent of high-technology trading, ought to teach us is that—like truth in war—it is common sense, not computer models, that is the first casualty of a financial mania.24 And much the same is true of failures in politics, business, and marketing. Bad things happen not because we forget to use our common sense, but rather because the incredible effectiveness of common sense in solving the problems of everyday life causes us to put more faith in it than it can bear.

TOO MUCH INTUITION

But if common sense is so bad at dealing with complex social phenomena like political conflicts, healthcare economics, or marketing campaigns, why are its shortcomings not more obvious to us? After all, when it comes to the physical world, we also have plenty of intuition that we use to solve everyday problems—think of all the intuitive physics that is required to chase down and catch a fly baseball. But unlike in the social world, we have learned over time that our “commonsense physics” is easily tripped up. For example, common sense tells us that heavy objects fall under the force of gravity. But consider the following: A man stands on a perfectly flat plain holding a bullet in his left hand and a pistol, loaded with an identical bullet, in his right. Holding both pistol and bullet at the same height, he simultaneously fires the gun and drops the bullet. Which bullet will hit the ground first? Elementary high school physics will tell you that in fact the two bullets will hit the ground at exactly the same time. But even knowing this, it is hard not to think that the bullet from the gun is somehow kept up for longer by its velocity.

The physical world is filled with examples like this that defy commonsense reasoning. Why does water spiral down the toilet in opposite directions in the northern and southern hemispheres? Why do you see more shooting stars after midnight? And when floating ice melts in a glass, does the water level go up or down? Even if you really do understand the physics behind some of these questions, it is still easy to get them wrong, and they’re nothing compared to the really strange phenomena of quantum mechanics and relativity. But as frustrating as it can be for physics students, the consistency with which our commonsense physics fails us has one great advantage for human civilization: It forces us to do science. In science, we accept that if we want to learn how the world works, we need to test our theories with careful observations and experiments, and then trust the data no matter what our intuition says. And as laborious as it can be, the scientific method is responsible for essentially all the gains in understanding the natural world that humanity has made over the past few centuries.

But when it comes to the human world, where our unaided intuition is so much better than it is in physics, we rarely feel the need to use the scientific method. Why is it, for example, that most social groups are so homogeneous in terms of race, education level, and even gender? Why do some things become popular and not others? How much does the media influence society? Is more choice better or worse? Do taxes stimulate the economy? Social scientists are endlessly perplexed by these questions, yet many people feel as though they could come up with perfectly satisfactory explanations themselves. We all have friends, most of us work, and we generally buy things, vote, and watch TV. We are constantly