Common Sense

A phrase first coined (in Greek) by MrAristotle. Your common sense is the quasi sense organ by which you perceive the "common sensibles" - the qualities in the world that transcend any particular sense organ, like shape (which you can sense through both sight and touch) and the essence or kind to which things belong, the causal powers that explain why things are the way they are, etc. I think the phrase is meant to describe the faculty of rational thought in a rather intriguing way.

Later redefined somewhat (misunderstood?) not as the inner sense that responds to what is common to different outer sense organs, but as a lowest-common-denominator collection of beliefs, prejudices, practical know-how, unexamined intuitions, and/or guessing ability thought to be possessed in common by nearly all people. Also used as a synonym for "horse sense", your ability to look at matters straightforwardly and not be confused by sophistry or book-learning.

Today, the term has so many incompatible meanings to so many different people, and is so bound up with so many hidden agendas and conflicting broader views of cognition, that it may be wisest to avoid it altogether. Some who appeal to common sense mean to shield their favorite cultural prejudices from examination and criticism. Some who appeal to common sense are just trying to pull you back into a state where you can acknowledge what you know to be true even though it doesn't fit into some theory you got from book-learning or abstract speculation.

-- BenKovitz


A rather uncommon ability to DoTheRightThing without a lot of forethought. A close connection to deep intuition.

-- MichaelDillon

Or, the very common ability to do the same old wrong thing again without any thought. A close connection to intellectual laziness.

See HeuristicRule.


CommonSense seems to be a collection of fixed NeuroPatterns?, StrangeAttractors and habits. At first, young people don't believe there is only one way of doing things, like education, etc. They are going to revolutionize the profession, etc. After three to five years, they just do the things like they always have been done beaten by the facts...

-- PieterJansegers (speaking out of experience)


My reading of this changed when I discovered common sense is based on experience. It is therefore not really common, and I'd rather it were called Experience Sense.

I found this out first when I went snow camping, and was told a bunch of things as being "simply common sense" which I had no clue about. A year later, they were simply common sense. Like keeping your socks dry. To a winter camper, the consequences of not keeping your socks dry are serious and well-known. To a non-camper, it is surprising that the idea has any consequences at all.

I found out subsequently, and most of all when I had children, that most of what falls under "common sense" can be backed up to experiences that the anticipated category of listeners is supposed to have had. I find myself explaining common sense items to children all the time. My mother used to say, "use your common sense" often. As a child and young adult I used to think she had deep intuition and I didn't. I now see her experiences and thinking ability in operation. -- AlistairCockburn

Where I see this cropping up frequently is where one or more developers hive off and do a piece of work by themselves. Or when new developers come into an established place. The word I hear is "complexity". As in, "the work you've done looks good, but it's too complicated. Isn't there an easier way to do this?"

Well, sure, there was an easier way, but it didn't work. The isolated developers found that out painfully and now it's obvious to them, but to new minds this is a deep mystery. People only ever really learn things the hard way.

So I guess all things start out mysterious and end up obvious. -- PeterMerel

I often find that sequence reversed... -- SteveFreeman

Curious. When do you see that?

(Speaking for myself, not Steve ...) I see both simultaneously, frequently with the same things. There are all kinds of things that used to be obvious to me - BigDesignUpFront is good, for example - that I now know are not obvious at all, and I wonder why people believe them. The reason that's no longer obvious to me is that a great number of things about the importance of coding early have become obvious, and I've learned a large number of CommonSense things that make my code now, with minimal upfront design, better than it ever was before.

Who was it that said "I'm not young enough to know everything"? -- GlennVanderburg I'm almost positive that was Oscar Wilde. It definitely sounds like the type of thing he'd say. If I had the time, I'd find out where he said it

I've seen it in the .sig of Erik Naggum on comp.lang.lisp. I don't know whether he was quoting from somewhere else. (He had "I'm no longer young enough...".) -- GarethMcCaughan

The situation I was thinking of was where you say, "Sure, I can do that", and then you get into it and find those tricky little details that make the world complicated. I'm also reminded of a line attributed to MarkTwain:

"When I was a boy of fourteen, my father was so ignorant I could hardly stand to have the old man around. But when I got to be twenty-one, I was astonished at how much the old man had learned in seven years." -- Steve


See Also: AllPanaceasBecomePoison


SteveCook told me that over time he has come to see so many sides to any issue or question that he is reduced to just asking questions instead of making assertions. I am in nearly the same state (he is either older or learns faster :-) -- AlistairCockburn

Isn't that the way Socrates liked to work, too? :-)

But he always got the answer he wanted.

No, more likely they only recorded the instances in which he got the answer he wanted.


I'm very old, but I learn very slowly. When fresh eyes look at something and say that it is too complex, I'd bet that they are right. Watching KentBeck refactor code has made me more certain of that than ever before. -- RonJeffries


Common sense keeps you circling the earth instead of flying through the stars. Careful, careful. It's only a shortcut. -- ss

If I learned one thing from the physics courses I did at university (a doubtful proposition), it's that "common sense" will utterly mislead you about the workings of the universe more times than not.


The current leadership of the UK Conservative and Unionist Party (somewhat like the US Republicans) touts a very, very frightening idea called the "Common Sense Revolution". It seems to consist in: bigotry, myopia, bourgeois petty-mindedness, isolationism, fear of difference etc. etc. After all, everyone knows that "immigrants are stealing our jobs" and so forth. Every time I hear those words: Common Sense Revolution it fills me with dread.


The closest German equivalent to CommonSense is "Gesunder Menschenverstand", which literally translates to "sound human sense". IMHO, this puts a subtly different spin on the concept: It's not necessarily common, but it's supposed to be "sound". -- FalkBruegmann


And the Hebrew equivalent of CommonSense can be literally translated as "straight thought" --YonatSharon

And here is a nice quan about it:

 Joshu asked Nansen in desperation: "What is the Way?"
 Nansen answered: "Common sense is the Way."
 Still tormented, Joshu asked: "How do you get on to it?"
 Nansen: "The more you try, the more you push it away."
 Joshu: "If you do not try, how do you know you are on the Way?"
 Nansen: "The Way has nothing to do with knowledge,
 but it is not not-knowing.
 Knowledge is an illusion; ignorance is blank.
 It is like vast space.
 Where there is no room for right and wrong."
 Upon this Joshu was suddenly enlightened.

The Mumonkan (koan 19)

(Or should this be in UncommonNonsense??)


"Common" also has the meanings of: mediocre, inferior, unrefined, coarse. With obvious application to "common sense".


Let's not forget Thomas Paine's "Common Sense" of 1776 which begins: "PERHAPS the sentiments contained in the following pages, are not yet sufficiently fashionable to procure them general favor; a long habit of not thinking a thing wrong, gives it a superficial appearance of being right, and raises at first a formidable outcry in defence of custom. But tumult soon subsides. Time makes more converts than reason." From http://www.americanfoundations.com/AFDoc.asp?doc=CommonSense


You could also consider CommonSense to be an extension of RolandBarthes' notion of ideology: A way to defuse all dissent by arguing that things are naturally and indisputably so. I know that when I'm listening to a politician and e says "After all, we all believe that ..." I get very suspicious of whatever comes next.

... CommonSense often isn't so common, after all.

... or perhaps it's sadly all too common, and simply wrong.


CommonSense in Human Relationships and Organizations is well explained and elaborated in HumanRelationsInOrganizations. An expensive book, well worth the price in the insights it gives the reader into the makeup and interrelationships which exist in any human endeavor.



[The following transferred from AnUnacceptableWayOfFailing. 2002/04/15]

''Project failures which result from: There are two distinct discussions here that I have attempted to unweave -- AlanChristiansen

Contention 1: The appearance that something could have been done better by the application of CommonSense is always much easier in hindsight.

Counter Contention 1: It is always easy in hindsight to find the 'apparently obvious, common sense' approach. It is not as easy during the midst of a project. That is why smart people do apparently stupid things. They were not stupid when observed from then only stupid when observed from now.

Contention 2: The acquisition of common sense can be a ConsciousLearningProcess?. Common sense can be learnt from people books. One can be careful, one can avoid being too optimistic etc. One can use known good problem solving heuristics.

Counter Contention 2: One can avoid being too pessimistic and optimistic, one can use known good heuristics such "Solve the difficult bits first" and one can go outside the square when obvious (in hindsight) common sense tells you too. Oops this definition is getting a touch vague ... Common sense requires the application of a large body of knowledge and wisdom to a problem. You can seek the knowledge, wisdom is a bit harder. I seek the wisdom to be able to apply my knowledge with balance judgement and due care (not excessive paralysing care) but I don't know how to start to tell you how you should seek wisdom.


Unfortunately, common sense usually results from failing. It is always easy in hindsight to find the 'obvious, common sense' approach. It is not as easy during the midst of a project. That is why smart people do stupid things.

I doubt that is true, in practice. InTheory one can do many things but when saddled with the reality of the species that is available for employment then the most common way that common sense is learnt is through the school of hard knocks. An observer of Humanity.

While that appears to be the most common way that common sense is learnt I have actually seen two people born with an uncommon amount of common sense. This is not terribly surprising since they also have been measured to posses uncommon amounts of ordinary (academic) sense. Same observer of Humanity

Common sense is often wrong. Perhaps what you mean is a lack of good people? That will always make a project fail.

The most unfortunate thing about common sense is that it is uncommonly uncommon. -- WhiteHat


I think the common sense (dominant) part of this topic is really trying to describe a well-developed sense of risk, which is the thing that's "uncommonly uncommon". It's hard to complete a single learning without at least one failure. It's hard not to fail at least a little on anything the least bit interesting. The question is not whether or not to fail, whether or not to learn. The question is how much can you afford to bite off and risk losing in one chunk? I guess if there's a "common sense" part of risk awareness, it's that SizeOfCommitment? is the main variable. -- WaldenMathews


I think the term CommonSense is pejorative. It is almost never used except in the negative: So-and-so should have used a little common sense when they did X. It is almost always used to criticize someone for doing something that they could have done better. When it is used in praise, it implies that the anyone could have duplicated what the doer did. (Excellent observation! (Soundly seconded))


To exercise CommonSense, one must put the brain in gear. Too often, people react with responses that are far out of line with the sensible reaction to a stimuli. Witness the growing number of "road rage" incidents which are triggered by what to many drivers are minor annoyances. Perhaps this is because driving has become more than transportation, having status, emotional and psychological components which are triggered by sensory rather than mental inputs. As an example, what did you think, versus what did you feel the last time some one displayed aggressive and unsafe driving. What was the common sense versus the actual actions you took in response? Be honest! Was your brain in control?


CommonSense Knowledge is also a term used in ArtificialIntelligence to describe concepts and rules that humans take for granted but which machines need to be given in order to operate appropriately in an environment. For instance:

  Water is wet, flows down, and will cause objects it contacts to become wet.
  If A is in B and B is in C, then A is in C
  If A is under B and B is under C, then A is under C
  A is attached to B and B moves, A moves with it.
  The sky is dark at night and blue during the day if it is not cloudy
  Action1 occurs during Event1 and Action2 occurs during Event2 and Event2
    is after Event1 implies Action1 is before Action2
  ....etc

Special Logics such as TemporalLogic and formalisms like NaivePhysics (QualitativePhysics?) are used to organize such statements. There is a project called OpenMind? http://commonsense.media.mit.edu/cgi-bin/search.cgi that is a web based portal (similar to wiki) that lets anyone enter common statements. At this point (early 2004) it does not allow querying of the data by the public, just input. CycMergedOntology also uses CommonSense reasoning. We should give pause to deleting wiki pages even if they seem OffTopic as any valid knowledge in a public structured forum such as wiki could be used for a CommonSense database later on. In my opinion, wiki has a lot less noise and threading than a newsgroup and each topic more compact. It has more context than OpenMind? (though they could complement each other).

A good book on the subject is ISBN 0893912131 "Formal Theories of the CommonSense World"


I'm finding that people are talking about completely different things here. Anyone care to prove me wrong? Because I'm having trouble making sense of it. Then again, Common Sense has always been a mysterious thing to me. I just know that, from the way I've heard people use it, it's not that common. -- JasonEspinosa


CommonSense is a property of minds that makes it possible for them to see the BloodyObvious (which see).


See also CommonBloodySense, CommonSenseIsnt, BloodyObvious, CommonSenseIsAnIllusion


Common sense is, according to Albert Einstein, "the set of prejudices aquired by age 18."


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