I have been thinking about common sense for years. I would lump it in with other forms of practical wisdom that function at a middle level of abstraction, along with proverbs, anectodal reasoning, and nuanced judgement. They are an adjunct to philosophical reasoning, which can be too complex and time-consuming to use in dealing with everyday situations in real time. In later essays, I will examine the psychological and epistemological aspects of these forms of knowing with a particular eye toward oral versus literate thinking. But let's begin with plain common sense.
I recently took part in a discussion of common sense in the r/philosophy subreddit. It was a great discussion. Almost all the commenters had serious reservations about common sense. I think I was the only one who was at least mildly in favor of it. Their objections to it can be boiled down to three points:
The concept has no definition.
It is culturally relative and is therefore not objective or universal.
It can be used as a bludgeon to attack people who disagree with you, without you giving principled reasons for your position, i.e. “If you disagree with me, it’s because you lack common sense.”
I acknowledge these objections, and they do instill a degree of wariness in me, but I think they can be overcome.
Ayn Rand said something interesting about common sense in her essay "Don't Let It Go"
Americans are the most reality-oriented people on earth. Their outstanding characteristic is the childhood form of reasoning: common sense. It is their only protection. But common sense is not enough where theoretical knowledge is required: it can make simple, concrete-bound connections—it cannot integrate complex issues, or deal with wide abstractions, or forecast the future.
Rand's student Leonard Peikoff had this to add in his lecture series on the philosophy of Objectivism: "That which today is called ‘common sense’ is the remnant of an Aristotelian influence."
I don't think either of these claims is quite right. Common sense can deal with more than concretes, because it can deal with middle-level abstractions, such as qualities of character, and it can to some extent forecast the future. And people who are not influenced by Aristotle seem capable of it. I've read about leaders of indigenous tribes who have something that could rightly be called common sense. Still, I think Rand’s and Peikoff’s ideas are a good jumping-off point.
I am not sure I can give a formal definition with a clear genus and a single differentia, but I think I can identify some crucial components of common sense, that may together function as a definition.
First, for a person to have common sense they must have a store of "common knowledge" about how the world works. They would have to know, for example, to look both ways before crossing the street and that people can't live on candy.
Second, they must have a reality orientation, at least while they are exercising their common sense. They might have a compartmentalized area of otherworldly faith or dogma, but when they deal with non-philosophical issues, they usually live in the real world. I've seen serious mystics who almost seemed to have split personalities, where one was the mystic and the other had common sense in buckets.
Peikoff would attribute the reality-orientation to the remnants of an Aristotelian influence, but I think that the universal human ability to stay close to perceptual reality along with the demands of living in the real world may account for good practical judgement. You don’t need a formal philosophy to know that you must work to keep your kids from starving.
Third, they must exercise what I call "critical thinking lite" skills. They must be able to do basic analysis and integration using simple, middle-level principles, including proverbial wisdom. An example of a proverb might be "You can't cheat an honest man," and the common sense application might be a matter-of-fact identification of the fact that the person being cheated engages is wishful thinking i.e. self-deception, i.e. dishonesty with himself. I wouldn’t call that concrete, and it doesn’t require Aristotle to understand it.
Speaking of proverbs, someone on Reddit pointed out that proverbs can be mutually contradictory, e.g. "Look before you leap," and "He who hesitates is lost." I don't think that this is an issue because proverbs aren't the stuff of philosophy, which has to be systematic and coherent. They are rules of thumb that help the user formulate their thoughts in different contexts. If common sense is a form of judgment, then rules of thumb are its heuristics. (For more about heuristics as well as cognitive biases, see this.)
Part of critical thinking lite is staying calm, reasonably non-reactive, and not letting emotions interfere with one's judgement. There's often an element of shrewdness to the use of common sense. This is what I have read about in the leaders of non-Western indigenous people.
Can we put these components together to make something like a formal definition? Let's try.
Common sense is an exercise of practical wisdom based on having a store of knowledge about how the world works, engaging reality, and using informal critical thinking skills on a middle level of abstraction.
To return to the three objections:
We do now have a workable definition.
The phenomenon is not culturally relative because we are restricting it to dealing with reality and not culturally relative beliefs such as religious dogmas. I realize we're in danger of the No True Scotsman fallacy here, but I think we can separate the pre-theoretical connection to reality of the common sense person from the often detached-from-reality quality of many philosophical/religious beliefs.
The charge that claiming a truth to be common sense is a way to bludgeon people who disagree is more difficult to answer, but I would note that claims that one is being logical, rational, or even kind can be used as bludgeons against people who disagree as well. If you’re worried that you might be bludgeoned, demand reasons, and if you worry that you might unwittingly bludgeon someone use, well, common sense introspection.
I can understand that some readers might still find the concept of common sense too nebulous for objective use. It might be helpful to work through an example of someone who, I think most people would agree, has little common sense. Let's call him JP.
JP did two years at a good college before dropping out. He clearly thought hustle would get him ahead in the world, so he sold nutritional products door-to-door, among other things. He kicked around for a while and ended up doing a year at another college. He didn't finish.
Soon he picked up enough skills to make an OK living at a job that was white-collar but beneath his talents. He still had side-projects. He tried to invent variations on products that were already so well-established that he never would have overcome the inertia that they had in the market, but the challenges fascinated him, even though he should have known the work would lead nowhere.
Although he had slept with a few women in his life, he mostly liked men—younger, browner men. (JP is white.) He couldn't find anybody suitable here in the States (this is before Grindr, so it might have been difficult to search). So, he did some research and lined up 24 men in their early 20s in Southeast Asia as prospects. He established a business partnership (not with one of the 24) and moved there.
Well, of course he got defrauded and lost most of his savings. He ended up living in squalor with one of his boyfriends, while doing online office work for fifty cents an hour. Next, he got run over in traffic, resulting in brain damage, which he treated by himself with the help of Dr. Internet.
I think you get the idea. JP just had no clue about how to navigate the world. And he couldn't understand why he annoyed some people or why they made fun of him. He just thought that people were being unfair to him for mysterious reasons.
I'll tell one more story to make my point. We lived together for a time after he dropped out of college. Once I did something nice for him—I don't remember what—and he became quite concerned that he needed to something equally nice for me, basically right away. His idea of kindness was strictly quid pro quo. I had to explain that friends don't keep score (although I suppose one has to have some sense of balance in order not to be taken advantage of).
I've lost track of him, but the last I heard about him was so awful that I do not want to repeat it. I don't think he has given up though, and he is back in the US where he can be better taken care of.
So, there's my example of a lack of common sense. He did hold a vaguely Objectivist worldview when he was in college the first time, which helped him a little, and he didn't have a mean bone in his body, but he almost completely lacked the store of common knowledge that people need to thrive and his critical thinking skills were extremely rationalistic, although he had practical skills such as fixing cars.
It's tempting to opine that JP was on the spectrum. Maybe. But he could hold normal conversations beyond his areas of interest. He made eye contact. He didn't have meltdowns, etc. I think his family was kind of strange, too, so maybe there is some sort of nature/nurture problem there. Perhaps he was neuroatypical in some other way, I don't know. He just seemed to lack common sense. And I think that someone from any other culture who thought and acted the way he did would be said not to have it as well.
I believe JP was a good example because you cannot attribute his problems to low intelligence or bad intentions. His lack of common sense, if that really is what was going on with him, seems just to be a character flaw. He could be person out of either a Shakespearean tragedy or comedy, depending on how you want to look at him. I for one don't want to laugh at such a fundamentally decent human being although many people who knew him did.
To conclude, common sense is a fairly effective way for a non-theoretical person to deal with the world. In fact, since most of philosophy is false and deleterious, common sense might be a better way to operate than theory much of the time. At the very least, a person with common sense can be a breath of fresh air, given their down-to-earth way of living.
I wrote in the comment section of another one of your essays that the subject matter had been on my mind—the same is true for this essay too! I was thinking the other day about two different "worlds" I've experienced. I've experienced the worlds of people who, like the essay explains, have common sense. And I've experienced the worlds of people who look at themselves as if they're philosophical gods (all-knowing; therefore I'm not worth their time or a proper conversation). I've come to the conclusion of, give me common sense people over the "philosophically" gifted any day (of course, this does not apply to every situation. For instance, I greatly enjoy our discussions). One thing I notice about people like you mention, who are smart, capable, and can participate in those middle levels of abstraction, they often come off much smarter to me than these philosophically intellectual types because they are actually so much more grounded in reality. I'll give you an example. Some time ago, I attended a meeting of "philosophical" minds. They were okay. But I quickly realized they lacked any kind of understood decorum because they not only had an inflated sense of self, but like you said, I also felt maybe they were "neurodivergent" (at least I think I'm using that term correctly). We met at a restaurant, a sports bar style place, and the music was just a touch loud. The bar was full. While we were there to chat, the rest of the establishment was enjoying the music. We were having a bit of trouble hearing each other. When the waitress came to take our order, one of the people at our table told her to turn the music down. I immediately, and calmly, told him that's overstepping a bit. He understood and told her not to worry about it. I'm not saying people should never ask staff to turn down music, but given all the context, that we weren't the only ones there, and there was a venue full of people enjoying the music, to me, it should have been evident that one should not ask for it to be turned down. Then, on the topic of government "welfare" programs, when I went into the rampant abuse within the system (obviously that's not the case with everyone, but members of my family have great working knowledge of the abuses within these programs due to their jobs), the table couldn't believe that people could be dishonest like that, and use government funding in ways the funding wasn't intended to be used. Then, on the topic of women (I was the only woman there), they were talking about women's biology using completely unfounded claims they thought were true simply because it fit their narrative of what "women" are. I tried to offer evidence-based context as to why they were wrong in their thinking. They literally laughed it off. THEN, later on, a rumor was spread around the group that I had a drinking problem... I ordered ONE scotch and water over the course of a period of several hours. Every time I attempted to make a point grounded in reality and based on evidence, I was brushed off. It was a terrible experience, and unfortunately, one that's not an isolated incident. These people literally thought their brains were God's gift to the universe. Major Superman syndrome. I came to the conclusion that, each instance that rubbed me the wrong way stemmed from them not being rooted in reality, and having this significantly inflated sense of self. On the other hand, I have many friends who I would say have "common sense." I greatly enjoy my conversations with them. Mostly, because they understand reality. And they understand NUANCE. That's a huge one. So many philosophical types are rationalists, especially when they claim they aren't. I notice running themes of these people who I'd say have common sense. Though they probably couldn't define "epistemology," they do have a grasp on reality, they do understand how the world ACTUALLY works because they live in it, they don't simply wax poetic about it. And the biggest thing that they posses that I admire is that we spend more time asking questions to each other and bouncing ideas off each other than talking at each other because we each think we're smarter than the other. It goes back to that first point I made, they understand courtesy. They have empathy. They are genuinely curious because they're smart enough to admit that they don't have everything all figured out. I so enjoyed your essay because you went through the process of not only defining common sense, but mapping out its concepts. In a culture in which I believe common sense is quickly draining, and most are chasing pseudo-intellectualism, your work you've done so far on the subject is super important.