And why it’s a bad tool in most contexts.

At the time I’m writing this piece, the COVID-19 pandemic still forces most European countries to impose restrictions on their population, such as more or less drastic confinement at home.

I live in Switzerland, and the federal government decided to not apply drastic confinement measures –unlike neighboring France or Italy– but instead invite people to stay at home and limit travels to absolute necessity. Of course, there are measures in place, such as a huge reduction in public transport, some public places & all non-necessary markets closed. Most companies sent back people at home weeks ago. But for the rest, the government officially relies on its population’s own discipline.

The Swiss Federal Council – Source

Indeed, Swiss people are known to be quite disciplined. Switzerland is often qualified as the “Japan of Europe”, and you can basically lose your wallet on the train it will come back to you with everything left inside or let your car open with no fear.

Un-common sense

But in this long sunny Easter weekend (4 days holidays), the temptation to go outside is high. During its recent message to the population, the Federal Council called for people’s common sense and accountability to avoid domestic travel, limit regroupings in public places, and even avoid certain activities that put you at risk –and could lead you to occupy a scarce bed in the hospital. For weeks, the government repeats the same call for people’s common sense.

But, unsurprisingly, today, the first day of the holidays, a lot of people are outside.


See, common sense IS NOT an equally distributed thing. In other words, common sense is only common for those appealing to it. As the study of group dynamics shows, it appeals to a limited set of shared values and understanding. The more strongly homogenous a group’s individuals are (on certain subjects), the more “common sense” exists. Therefore, common sense is not an absolute thing.

Ethical implications

Calling for people’s common sense is the same as telling them to follow what they feel is right. This moral subjectivism leads to everyone’s right to judge the situation based on their own feeling. If you feel this pandemic is overrated, why would you stay at home? If you feel your need for fresh air is more important than the risks, why stay at home?

Logical fallacy

Appeal to common sense is the assertion that a conclusion or facts are just “common sense” when, in fact, they are not. In its logical form, we can observe:

It's common sense that X is true.

Therefore, X is true.

Even though something is “common sense” this wouldn’t make either true or good. This fallacy is often used to support a proposition without the need to provide strong arguments or actual evidence.


Common sense is a bad tool to use, either in a prescriptive way or as an argument –unless one is able to demonstrate the commonality and likelihood of the proposition. “Common sense” is a form of sophism that can push people either to conformity or individualism.

I observed this situation several times as a designer when, for instance during a meeting, someone asserts something (knowingly) without evidence and tries to convince the majority of their truthness. Designers are subject to such fallacy as well. We often assert the commonality of such and such behavior, mainly because we read or heard it from some authority –this is a faulty generalization.

If “common sense” is your best justification for any conclusion/proposition, ask yourself how do you know such a thing. Ask what would disprove it to be true. Try to build a better argument.

If you’re a designer, remember that no authority is better than you to validate if a certain behavior occurs in your specific context. This is an invitation to systematically test your assumptions and build a case for your observations & decisions.