Common sense is extremely uncommon. It does not refer to any specific amount of information but relates to practicality and foreseeing predictable consequences at least as well as a person of average knowledge within a certain milieu. In artifical intelligence, it has some relation to the frame problem.

Two words, used to represent the socially stimulated phenomenon of experiencing and judging one's surroundings in a way that is structured like the experience and judgements of the dominant group in these surroundings. The contents and borders of this phenomenon are identified by formulating and pointing out the approaches or ways of thinking that do not belong to this 'common sense.'

Evolution optimized our brains with certain cortex-hardwired faculties that quicken learning and ease decision making. While no one has yet claimed to have definitively isolated them all, Steven Pinker used his encyclopedic knowledge of the state of the sciences of psychology and neuroscience to put a stake in the ground in his 2002 book The Blank Slate. Here are the eleven core faculties that he identifies.

  1. Simple Physics: (We intuitively know that...) Objects persist in space and time. When they fall, bounce, and bend, they follow consistent laws of motions and force.
  2. Simple Biology: All living things possess an invisible essence that gives them their power, drives their growth, and is inherited by their progeny. A dead thing no longer possesses this invisible essence.
  3. Simple Engineering: Certain objects made by other people can be used to ease work. Recognizing the functions of these objects and the intentions of the designer is easy.
  4. Simple Psychology: Other people are similar to you in that they possess thoughts and motives which drive their actions. (Called the theory of mind.)
  5. Spatial sense: We know where we are in relation to other things. We know where to move for greater protection from or access to something.
  6. Number sense: Small numbers of objects are easy to quantify. Larger groups of objects are easy to compare.
  7. Simple Probability: We can predict the likelihood of certain events based on intuition and past experience.
  8. Simple Economics: We have an innate sense of fairness in the exchange of goods and favors.
  9. Mental database & logic: We can generalize knowledge, apply knowledge, and create new hypotheses with operators such as AND, OR, NOT, ALL, SOME, NECESSARY, POSSIBLE, and CAUSE.
  10. Language: We easily adopt spoken language that enables us to share our mental database and logic. This includes a memorized vocabulary, rulesets for combining these words into sentences, and memorized exceptions.
  11. Simple Morality: Certain people, objects and land are worth our protection and respect. (Called our moral circle.) People, objects, and land outside of this group may be subjugated.

He also identified two other faculties worth mentioning, but they are probably better categorized as emotions as they are driven more by the amygdale rather than the cortex. Still you can imagine someone saying, "Ain't you got the common sense to...?"

  • Fear: We can quickly and fairly accurately assess danger.
  • Disgust: We can intuitively assess contamination in people and objects.

This collection of faculties is, if anything, what can be called common sense. (It even fits Sir W. Hamilton's definition, "The complement of those cognitions or convictions which we receive from nature, which all men possess in common, and by which they test the truth of knowledge and the morality of actions.") No one has to teach kids not to run into trees, or that one kitten is fewer than two, or follow peoples' gazes to see what interests them. It's ingrained. Common.

It will probably be a while before neuroscience or psychology can authoritatively confirm or refute Pinker's list. But presuming he's close, so what?

I work in the field of Human-Computer Interaction, so it's quite useful for me, when I'm building interfaces between processors and brains, to understand what people are naturally good at, what faculties they may bring to bear to a given task, and what instincts guide their guesses when things go wrong.

But even people outside of my field can benefit from this awareness, because these instincts can hinder life in the modern world. How can this be? If evolution built them (and they sound pretty good to me) aren't they reliable? Well, not entirely. These common senses are very functional in the Pleistocene nomad's world of illiteracy, woolly mammoths, and a carrying-capacity limit to possessions, but we don't live in that world. (The gene may be selfish, but it's damned slow.) The world we live in has new, unintuitive areas of knowledge we must grapple with and edge cases where these instincts are wrong.

Unintuitive Knowledge

We can bring some of common sense to bear for the first problem of vital but unintuitive knowledge. That's what we're doing when we teach children to read and write using their natural mastery of language. It's why your mathematics teacher kept telling you to draw out word problems, to get you to shift from tough abstract reasoning to the easier task of working with spatial relationships. We hijack our simple engineering sense to understand the details of complex biology, as we comprehend each organ as a widget with a function. Generalizing this, when you're faced with a tough problem in an unfamiliar field, change your approach to the problem through one of your common senses, and you'll probably be more effective. Similarly, when you're teaching a complex subject, build on your student's common senses, and you'll probably have more luck.

Edge Cases

More critically IMHO, as science pushes our understanding of the universe and our selves, we are confronted with new complexities and edge cases where these instincts are actually dysfunctional, or wrong. Sometimes this is a matter of scale, as when particle physics confounds our Newtonianish instincts. But often this occurs where a sense is over-applied. For instance, the concept of a soul derives from our biological sense and our theory of mind. It worked pretty well for telling whether someone or something was either dead or alive. But modern science is presenting us with questions for which the concept of the soul does harm. For instance, this concept led ideologues in the Roman Catholic Church to outlaw condoms, even at the expense of overpopulation, unplanned parenthood, and devastating sexually transmitted diseases. Recognizing such dysfunctional sense will become even more important as the world plunges further ahead into the unfamiliar world of biotech.

Similarly, our common sense for simple engineering causes lots of cognitive dissonance for people struggling to reconcile evolution with their intuition that design implies a designer, and so we get Scopes Monkey Trials and Mississippi textbook warning labels.

None of this means we should abandon common sense (if we could). It is generally a useful thing. What it does mean is that we should recognize our common sense for its origins and limitations, and keep a skeptical head about it. Common doesn't necessarily mean good.

"Common sense" has been discussed throughout human history by philosophers, scientists, mystics, and other people with large brains, yet it remains a curious and elusive subject because it is so uncommon.

The term is an English adaptation from an ancient Semitic language, but for simplicity's sake we'll call it Yiddish. "Common" is derived from the roots Kham and Ahn, which literally mean "Oy vey, come on you dimwitted klutz." Its earliest usage can be found in the Torah, when Moses and the Israelites were about to be recaptured by the Egyptians at the shore of the Red Sea:

Moses: O Lord Almighty, thou has led us this far in thy infinite wisdom and generous application of miracles, and we are most grateful.

God: Well then, why do you call upon me, if you believe I have done well for you? For I know you people too well to think that you would call upon me just to say "thanks," and therefore I ask that you tell me just what is bothering you now.

Moses: It is just so, my Lord, that the armies of the Pharaoh are closing in upon us, and we have found our escape blocked by a rather large and deep body of water (the Red Sea, no less), and not one of us is dumb enough to believe we can swim across.

God: Kham Ahn, Moses. I've got it all planned out; just jump into the water.

As the above passage indicates, using common sense generally yields great benefits. Unfortunately, laboratory tests have proven that jumping into the Red Sea rarely does the test subject any good, which suggests that common sense, even coming from God, tends to become outdated and new forms of common sense must be developed as needed.

This is made difficult, however, by the fact that common sense cannot be observed directly. Indeed, no one has actually seen common sense, but we infer that it exists because we can see when someone obviously isn't using it. As such, developing formal rules of common sense is extraordinarily difficult, and involves waiting for somebody to do something really stupid, and then one can try to determine what the commonly sensible thing to do might have been.

For example, suppose some fool lights his pants on fire with a match. He gets severely burned, and now has half of a pair of pants. Based on this, we can determine that if this person had used common sense, he would have taken his pants off first, soaked them with lighter fluid, and then set them on fire. This would have prevented the burning and gotten rid of the pants more efficiently.

Hopefully, the reader now has a better grasp of common sense and how to find it. Good luck!

Common Sense is the name of a pamphlet written by Thomas Paine, meant to justify the concept of American independence. It was published in 1776, when the question of whether the nascent American Revolution would be fought to force Britain's parliament to be more equitable with the colonies, or whether it was a true war of independence. Paine argued that America should fight for total independence.

As a student of American History, I have heard this book referenced for years, but had never read it. It is especially regrettable that I hadn't read it since, as mentioned, it was originally a pamphlet, and in a modern format it is still under 100 pages and can be read quickly.

One of the things that I found while reading "Common Sense" was that, like much of the writing of that era, it has been retroactively turned into an icon. Just as the actual Constitution of the United States of America deals more with the structure of government than statements of principles, "Common Sense" deals more with the immediate crisis of American politics at the time than it does with intricacies of political philosophy. Of course, that is to be expected, because even from the title, we know that the book is "Common Sense", a book meant to be about immediate concrete problems and the solutions to them.

Which is not to say that this is still not an important book to read. Also, it was not the only book that Paine produced, and I believe some of his other works were more philosophical in character. But this was Paine's best seller, and the work that was most important as a piece of propaganda that effected popular opinion at the dawn of the American Revolution. It is important to read to understand the sentiments, rather than the just the ideas, of the American patriots.

It is also, like so much related to the American Revolution, a book that is easy to misquote and misconstrue out of context. For example, the closing words of the work are:

mingling religion with politics, may be disavowed and reprobated by every inhabitant of AMERICA.
Which makes a good soundbite to suggest that Paine was against religion in politics. Of course, the argument is somewhat weakened in that in the same work, Paine also includes a quite lengthy argument from scripture against the concept of monarchy. In other words, Paine, like many of the founding fathers, was much less systematic and consistent than some might think. Which is one of the reasons why this work should be read in its whole, and not just alluded to--- to avoid taking a single line and misconstruing the philosophical background it came from.

Com"mon sense" (?).

See Common sense, under Sense.


© Webster 1913.

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