Common knowledge is information that is generally known by most people, and everyone knows that everyone else knows it.
This can include:
- Well-known facts
- Widely-accepted ideas
- Social norms, and
- Cultural concepts
But beware: common knowledge varies from society to society.
What’s common knowledge to you may not be common knowledge to someone on the other side of the world or even a different subculture in your city.
For example, it’s common knowledge among Christians that Judas betrayed Jesus. They were taught this lesson throughout their childhood.
But ask your Hindu friend down the street, and it may not be so commonly known to them!
As a result, “common knowledge” is a subjective and context-dependent term!
Definitions of Common Knowledge
One key feature of common knowledge is that it has to be known by a vast majority of people. But furthermore, people need to know that other people know that knowledge.
Here’s how one scholar says it:
“An event is common knowledge among a group of agents if each one knows it, if each one knows that the others know it, if each one knows that each one knows that the others know it, and so on.” (Geanakoplos, 1992).
This is an important detail if we take a case where ten people are in a room and they all know a fact, but they don’t realize that the people around them also know it! In this case, the thing is widely known, but not acknowledged to be common knowledge, because people don’t realize other people know it!
Common Knowledge Examples
Examples of Common Knowledge Gained Through Education
- The Earth is round.
- There are 365 days in the year.
- Water freezes at 32 degrees Fahrenheit.
- The French word for thankyou is “Merci”
- The capital of the United States is Washington, D.C.
- Humans have five senses – sight, smell, hearing, taste and touch.
- The colors of a rainbow are red, orange, yellow, green blue, indigo and violet (ROYGBIV).
- Oxygen is essential for human life.
- Gravity keeps us grounded on Earth.
- Objects in motion tend to stay in motion unless acted upon by an outside force.
Examples of Common Knowledge Gained through Experience
- If you touch something that’s hot, you will be burned.
- If someone finds out you lied to them, they will be offended.
- If you don’t wear sunblock, you will be sunburned.
- If you look at the sun, your eyes will hurt.
- Don’t touch wild animals.
- Books make you smarter.
Examples of Common Knowledge Gained through Social Norms
- It is polite to say “thank you”.
- Children aren’t allowed to drive.
- You need to respect the police.
- It’s polite to make eye contact with people.
- It’s polite to turn up to an appointment on time.
- If the teacher is talking, you need to be quiet and listen.
- Don’t talk in the library.
- Wait in line for your turn.
- It’s rude to tell people your income.
- Dresses are designed for women.
Sayings and quotes about Common Knowledge
- You catch more flies with honey (You’ll get your way more if you’re nice!)
- Let sleeping dogs lie (Don’t stir up trouble!)
- Don’t kick the hornet’s nest (Don’t stir up trouble!)
- If you don’t have anything nice to say, don’t say anything at all.
- The early bird gets the worm (Wake up early to have a good day)
Common Knowledge vs Common Sense
Common sense and common knowledge are terms that overlap, so examples will be similar.
Generally, common sense refers to things that are easy to deduce through logic.
For example, “don’t touch the hot plate” is common sense, but it’s also common knowledge.
Of course, we rightly assume that if something’s common sense then it’s also common knowledge.
But sometimes, people who lack street smarts might do things that aren’t common sense. One embarrassing example from my life was in science class, where we were given a science experiment involving acid. I touched the acid and said “wow, that tickles.” My friends looked at me like I was a fool.
The teacher thought this piece of common sense was such common knowledge that she didn’t bother telling the class not to touch the acid.
Here, we can return to the definition of common knowledge: everyone must know something, and everyone must know that everyone knows it.
By contrast, with common sense, you can know common sense because it makes sense and you would usually assume that others know it intuitively – unless they’re foolish, like me.
Migrants and Common Knowledge
Immigrants often find it very difficult to fit into a society because they’re often unaware of a culture’s common knowledge. This leads to culture shock.
For example, a migrant to my city of Vancouver might not realize that it’s common knowledge that you need to get a tap-on tap-off card to use public transit.
The migrant might get on a bus and try to give the bus driver cash. The bus driver will look at them like they’re ignorant.
They’re not ignorant, of course. They just lack common knowledge because they haven’t been in the society long enough and don’t have the social capital required to learn the things that are common knowledge in the society.
Common Knowledge and Cultural Capital
Common knowledge can be seen as a type of cultural capital. This is a term that refers to how well you know and fit-in within a cultural group.
In the example above of the migrant on the bus, they lack cultural capital in the form of common knowledge.
Turning to scholars like Pierre Bourdieu, we learn that cultural capital can be developed through time in the culture, education within the culture (see: cultural capital and education), interaction with peer groups (social capital), and even by paying to learn about it (economic capital).
Common knowledge refers to information that is known by a group of people, and all people know that other people know it.
But as we’ve seen, common knowledge isn’t quite so common! If you move to another culture, you may find that you lack the common knowledge that all the people around you have!
Similarly, if you go back five years, new facts and even modern sayings and songs are not commonly known at all. So, what is considered “common knowledge” is always changing depending on the social and cultural context.
Dr. Chris Drew is the founder of the Helpful Professor. He holds a PhD in education and has published over 20 articles in scholarly journals. He is the former editor of the Journal of Learning Development in Higher Education.