I first started getting bothered by the notion of "common sense" many years ago enough so that almost exactly five years ago back in May of 2015 I started the draft for this article. While recent events have changed the world, I think "common sense" was just as suspect a concept back then as now.

I'm not commenting on some sort of inexorable decline of "common sense" in the populace. Complaining about how the world is getting less cognitively sophisticated is a super old tradition that I'm not wishing to take part in. In fact to quite the contrary I think due to the vast amount of knowledge out there these days people are able to think more clearly on average when compared with past eras if they wish to do so. Most people who voice concerns about "common sense" in that manner I find are just using it as a proxy to say that their decision making is superior to someone else. I find this particular variety of usage utterly perplexing, the argument that there's this notion of "common sense" but yet somehow most people don't have it. In fact I've even had someone say to me recently "hardly anyone has any common sense these days", in a twist of great irony when I pointed out the contradictory nature of this statement I was lumped in with that category who lack "common sense".

While it would be tempting to say that I have "common sense", I really think this is a trap and would be intellectually lazy in the extreme. Instead what I'm saying is that in the way the phrase is often used common sense doesn't exist in a universal way.

If you've like me had doubts about the phrase, I think this is likely because it's actually a fundamentally unsound concept. And like anything that challenges a short soundbite or commonly held position it will take a bit of explaining to outline what I'm getting at.

In response to a rapidly evolving pandemic situation with massive impacts on health, economics, politics and just general culture, we have seen a lot of changes lately. All this from a disease that didn't even exist half a year ago. But nonetheless people are saying that we should have a fully formed "common sense" to deal with this situation. Having a fully formed consensus as to how to deal with a complex health and logistics crisis only months from it starting is clearly absurd, but I think the temptation to gloss over the details is an integral part of many appeals to "common sense".

A great example was today someone claiming that "we need a multinational inquiry into the coronavirus pandemic that covers all the different political systems and countries involved and looks at how they handled their health systems. This is obvious. This is just common sense." We have a situation that:

• Was caused by a pandemic from a virus that didn't exist even a year ago.
• Has seen vastly different approaches taken to it by different countries due to differences in cultures, economic and legal system, geography and other factors.
• Had different health care systems and different health care policies impact it differently in different locations.
• Has had vastly different effects on local economies that have in turn big impacts on the balance of global economics, global economic policy, military policy, foreign policy and diplomacy.
• Had a massive ongoing response from health workers including research and development effort by a huge number of leading experts that has had huge changes. (The example of ventilators being initially used before being found to be a massively bad approach by frontline doctors being a good example.)

How to get to the bottom of all this doesn't sound "obvious" to me, even if we did reach some understanding of what's going on different people will have vastly different ideas as to what is best to do in response. It would be great if people were more sensible in their responses to this pandemic and the health policy decisions that are being made. The notion that there is commonality here is suspect at best, but highlights a vastly bigger problem. You'll find that most situations in life have a surprising amount of depth of detail to them, and that most appeals to "common sense" gloss over those details and frequently even beg people to gloss over those details. For something complex to be able to be felt to be understood broadly much of the details have to be omitted. The situations that don't have any depth to them might actually be the rare ones. In practice when "common sense" is being invoked not as part of a pejorative (which happens a lot) I've found that it is the act of glossing over details that leads to many of the problems when "common sense" is appealed to. (October 2020 edit: ironically as people are coming to understand the pandemic situation better and the depth of the issues are becoming more obvious to many the usage of the phrase "common sense" is being used less often now. I think this is the usual progression for any complex subject that becomes the subject of widespread discussion where many participants do not yet realize how much they don't know they don't know. When more people start to understand what they know and the boundaries of their knowledge they tend to start to question what other people know. If you are to actually educate anyone on a topic you have to be aware of any asymmetries of knowledge such that you can debase and question those topics. This questioning tends to quickly dispel any false sense of commonality of knowledge.)

Ask people to define common sense, see what people say. Bonus points if you ask for a rigorous definition. See if this definition can stand on its own.

This doesn't have to be a thought experiment, and might be better not as one, asking people to define this is very interesting. Did people agree with your definition of common sense?

Common sense as a pejorative

Before we get into looking at the concept I think it's important to note that there's a few different ways the phrase is used. I find a very large percentage of the time that "Common sense" has been invoked lately is as part of a pejorative or some other sort of criticism of someone elses approach to something. I think this idea of using common sense as a shorthand for "I don't like how someone approaches this, you should find my way of going about it obviously better" is better expressed in other ways if you actually want the other person to change their approach.

There's a not so great thing that can happen with people who frequently use "common sense" as a pejorative, it's that they stop thinking clearly about how other people think.

Cross cultural work

Some time in 2014 while I was working in Canada I decided to make a conscious effort to not use this phrase and marked it down as a note for creating this blog post. I had a moment of enlightenment during a conversation about a topic with a strong cultural component. Somewhere in the middle of this discussion I realized that the "common sense" we were referring to was really only "common" within the cultural context of the respective countries we were born in. ¹ "Common sense" is sometimes invoked as a dog-whistle term or as a shibboleth where the whole idea is actually to signal in-group status by showing how you have the "common" sense of that group as opposed to the "common" sense of another group. This might be one of the most damaging forms of "common sense", not to mention a brutally self contradictory one that requires substantial mental gymnastics and contortions to use if you have any aspirations to erudition. But this experience was just a regular misunderstanding due to an assumed common ground that didn't actually exist. Upon realizing that this phrase was artificially limiting my understanding of other cultures, I made a goal to completely eliminate my usage of this phrase in all my conversations.²

At first I just thought "common sense" was a phrase that inhibited cross cultural work. But after a year of not deliberately not using the phrase and being mindful of the times other people were using it, and how they were using it, gave me a few other insights. Specifically I found the usage of phrase (and other similar phrases) would frequently inhibit gaining a greater understanding of situations.

In the last few years I've spent a while bunch of time working in different countries. One of the most interesting things about working in different places is the difference in cultures you see at work.

To be effective in cross cultural work you have to recognize that there's a distinct lack of commonality in certain situations. To really thrive in cross cultural work you need to understand the cultural backdrop behind why people act they way they do and how the different groups have different cultures and histories.

The people who assume that other people think the same way as they do tend to struggle the most with cross cultural issues.

There's a book I particularly enjoyed reading called "The culture map" my Erin Meyer that talks about how there's a lot of differences between work cultures in different parts of the world. One of the central themes of the book is that people tend to overestimate personal differences while underestimating cultural ones. I think part of the reason why this happens is because if we have most of our interactions within the same cultural context we don't have to think about that context so much. The same can't be said of interpersonal differences, the differences between people just can't be ignored without a lot of downsides. When you ignore cultural differences things go badly but it's far less obvious what's causing it.

I remember someone in the States telling me that it's "common sense" that you must "Praise publicly, criticize privately" when talking about managerial matters. Turns out that other cultures don't go about this the same way and this can lead to all sorts of problems when you get overlap from people of different places.

One great way to get things wrong is to assume that there's a common understanding with regards to cultural history but talk and act like there is. I had the great fortune of having an excellent politics teacher, one thing he did was write a translation of a political analysis of the events of the dismissal of the Whitlam government into German. At the time I remember thinking this would have been tough, only much later when I was living and working as an ex-pat did I realize what a difficult task this would have been.

Let's say for the sake of argument someone could have said that John Kerr's actions were "common sense" given the situation, but how would you explain this to someone from Germany who hasn't had exposure to the Australian political system? Do you start by explaining the structure of the government in Australia? Do you start by explaining the role of convention in the Australian system? Or the role of the particular people involved in this constitutional crisis? How would you explain why it mattered if Kerr acted without talking to the Queen? Why is this still controversial now? Or would something completely different that I don't even realize is not in common with the German system need to be explained first?

Complex projects

On a professional level I've run into the phrase more than a few times recently. Usually in what appears to be absurd circumstances to any outside observer.

One place where we would be vastly better off not using this phrase at all is when we are dealing with projects with high levels of complexity and specialization. When you bring in external specialists you are using bringing them in because of differences in experiences and skills between them and your group. If you are bringing in specialists because they have different skills and experiences to the people on your team, then you will, by design, have a situation where common experiences do not exist for everyone in the areas that matter to you.

In logistics I'd heard about how a particular client "just didn't have common sense" with regards to a roll out of a completely new specialized system. I know this is the pejorative case I mentioned earlier, but saying "they don't have common sense" just isn't good stakeholder management. If you want someone to change what they are doing you are greatly helped by figuring out why they are going about things the way they, just calling them stupid is likely going to shutting down any conversation about change.

The more insidious situations are ones where there's no shared base of understanding. For example in a complex software development environment I've heard people refer to test driven development as "common sense" and also not using it to be "common sense". Opinions on what constituted "common sense" were anything but commonly held across the teams. Asking an expert to adjudicate on what is permissable as "common sense" is just madness, but a madness that happens more than I'd like.

Discussions of methodology that don't come with a blanket assumption of a shared understanding of the problem domain are likely to yield much better results. So talking about these decisions is helped enormously by taking an approach that encourages thinking about the informational-asymmetry that exists rather than denying it. Professionals should be making decisions of consequence based on their experiences and professional knowledge, and those experiences are going to be different. People even talk about how companies do better with a diversity of experiences and some companies explicitly go out of their way to get people with different perspectives as a result.

Assuming a common understanding is actually dangerous in some situations.

Specialized projects have decision making that hinges on the things that make those projects specialized. This complexity is often irreducible and the decision making process must accommodate this reality. If you try to decrease the complexity of your definitions due to a pressure to meet some complexity that can be understood by some "common" understanding you may miss the core of what is going on.

Using the term "common sense" gets people thinking they have a shared understanding when they might not. The problem is that people might not actually check if their understanding is shared because phrases such as this strongly tend to shut down discussion, not encourage it.

A closing thought

While I'm saying that I think the phrase "common sense" tends to be of dubious value this post is not a call to action to police speech. I think discussions of these concepts are far more valuable than any outcomes from censorship of the term.

Part of the reason I think censoring the term would be so bad is because this phrase is used so differently in so many circumstances and pejorative uses probably aren't the most common usage. One thing that's very noticeable is that for something that is supposed to be common to people is that it is surprisingly hard to find any rigorous definition of what people mean when they use this phrase. And I think this is no surprise, to explain the notion of what's commonly held to be sensible would first involve explaining the current cultural situation, its history and context, essentially explaining the zeitgeist. Any rigorous definition of common sense I've come to from thinking about this has had an extremely high Kolmogorov complexity. Kolmogorov complexity is the idea that you can get a sense of how complex something is by measuring the length of the shortest possible representation of that idea. A good description of the zeitgeist necessarily involves a huge number of references to other works just to explain the context and history driving the main themes not to mention the uncountable number of little aspects of what makes the current environment what it is. In other words to define what is meant by common sense without just making a whole bunch of assumptions I have been unable to find any way to do it that hasn't involved a lot of words.