Common sense is so ordinary that we tend to notice it only when it’s missing, but it is absolutely essential to functioning in everyday life. Common sense is how we know what to wear when we go to work, how to behave on the street, and how to maintain harmonious relationships with our friends and coworkers.
For something we refer to so often, however, common sense is surprisingly hard to pin down. Roughly speaking, it is the loosely organized set of facts, observations, experiences, and pieces of wisdom that each of us accumulates over a lifetime in the course of dealing with everyday situations. Beyond that, it tends to resist easy classification.
However, there are two defining features of common sense that seem to differentiate it from other kinds of human knowledge like science or mathematics. The first of these features is that, unlike formal knowledge, common sense is overwhelmingly practical; it is more concerned with providing answers to questions than in worrying about how it came by the answers. In contrast to formal knowledge, common sense does not reflect on the world.
The second feature is that while the power of formal knowledge resides in its ability to organize specific findings into logical categories described by general principles, the power of common sense lies in its ability to deal with every concrete situation on its own terms. For example, it is a matter of common sense that what we wear or do or say in front of our boss will be different from how we behave in front of our friends. Common sense just “knows” what the appropriate thing to do is in any particular situation, without knowing how it knows it.
As remarkable as it is, common sense exhibits some mysterious traits, one of the most striking of which is how much it varies across cultures. Several years ago, a group of economists and anthropologists set out to test how different cultures play a particular kind of game, called an ultimatum game.The game goes something like this: First, pick two people and give one of them $100. That person then has to propose a split of the money between himself and the other player, ranging from offering them the whole amount to nothing at all. The other player then gets to accept the deal or reject it.If the second player accepts the deal, they get what they were offered and both players go on their merry way. But if they reject the offer, neither player gets anything; hence the ultimatum.”
In hundreds of these experiments conducted in industrialized societies, researchers had already demonstrated that most players propose a fifty-fifty split, and offers of less than $30 are typically rejected. Economists find this behavior surprising because it conflicts with their standard notion of economic rationality.Even a single dollar, the reasoning goes, is better than nothing at all, so from a strictly rational perspective, recipients ought to accept any offer above zero.And knowing this, rational “proposers” ought to offer the least they can get away with―namely, one dollar.Of course, a moment’s thought suggests why people play the way they do―namely that it doesn’t seem fair to exploit a situation just because you can.Recipients being offered less than a third, therefore, feel taken advantage of and so opt to walk away from even a substantial sum of money in order to teach miserly proposers a lesson.And anticipating this response, proposers tend to offer what they assume the recipient will consider a fair split.
If your reaction to this insight is that economists need to get out a little more, then you’re not alone.If anything seems like common sense, it’s that people care about fairness as well as money.But when the experimenters replicated the game in fifteen preindustrial societies across five continents, they found that people in different societies have very different ideas about what counts as fair.At one extreme, the Machiguenga tribe of Peru tended to offer only about a quarter of the total amount, and virtually no offers were refused.At the other extreme, the Gnau tribe of Papua New Guinea tended to make offers that were even better than fiftyfifty, but surprisingly these “ hyper fair” offers tended to get rejected just as frequently as unfair offers.
What explains these differences?As it turns out, the Gnau tribe had customs of gift exchange, according to which receiving a gift obligates the receiver to reciprocate at some point in the future.Because there was no equivalent of the ultimatum game in the Gnau society, they simply “mapped” the unfamiliar interaction onto the most similar social exchange they could think of―which happened to be gift exchange―and responded accordingly.Thus what might have seemed like free money to a Western participant looked to a Gnau participant very much like an unwanted obligation.The Machiguenga, by contrast, live in a society in which the only relationship bonds that carry any expectation of loyalty are with immediate family members.When playing the ultimatum game with a stranger, therefore, Machiguenga participants―again mapping the unfamiliar onto the familiar―saw little obligation to make fair offers, and experienced very little of the resentment that would well up in a Western player upon being presented with a split that was patently unequal.To them, even low offers were seen as a good deal.
Once you understand these features of Gnau and Machiguenga cultures, their puzzling behavior starts to seem entirely reasonable―commonsense, even.And that’s exactly what it was.Just as we regard fairness and reciprocity as commonsense principles in our world that should be respected in general, so the people of the preindustrial societies have their own implicit set of understandings about how the world is supposed to work.Those understandings might be different from ours.But once they have been accepted, their commonsense logic works in exactly the same way as ours does.
What these results reveal is that common sense is “common” only to the extent that two people share sufficiently similar social and cultural experiences. Common sense, in other words, depends on what the sociologist Harry Collins calls “collective tacit knowledge,”meaning that it is encoded in the social norms, customs, and practices of the world.According to Collins, this type of knowledge can be learned only by participating in society itself.
One of the most important consequences of the socially embedded nature of common sense is that disagreements over matters of common sense can be extremely difficult to resolve.The American anthropologist Clifford Geertz noted in his study of witchcraft in Java that “when the whole family of a Javanese boy tells me that the reason he has fallen out of a tree and broken his leg is that the spirit of his deceased grandfather pushed him out because some ritual duty has been inadvertently overlooked, it is precisely what they think has occurred, it is all they think has occurred, and they are puzzled only at my puzzlement at their lack of puzzlement.”Disagreements over matters of common sense in other words, are hard to resolve because its unclear to either side on what grounds one can even conduct a reasonable argument.
Whatever it is that people believe to be a matter of common sense, they believe it with absolute certainty.They are puzzled only at the fact that others disagree.
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