Common knowledge refers to widely known, generally accepted, and easily verifiable information by a broad audience. The shared knowledge is considered common sense or widely disseminated within a particular field or society. 

This type of information is typically not attributed to a specific source because it is considered common knowledge within the given context. In academic writing, one of the fundamental principles is to provide proper attribution and citation for any ideas, facts, or information that is not considered common knowledge. 

Examples of common knowledge

Here are some examples of common knowledge:

Basic facts

Widely known historical events, scientific facts, and general information that is readily available in multiple sources, such as:

  • The Earth revolves around the Sun.
  • The American Civil War took place from 1861 to 1865.
  • Water freezes at 0 degrees Celsius (32 degrees Fahrenheit).

Common sayings and proverbs

Popular phrases, idioms, and proverbs that are widely known and used in a particular culture or language, such as:

  • The early bird catches the worm.
  • A picture is worth a thousand words.
  • When in Rome, do as the Romans do.

Well-known quotations

Famous quotes from historical figures, literary works, or popular culture that are widely recognized and referenced, such as:

  • “To be, or not to be, that is the question.” (William Shakespeare)
  • “I have a dream…” (Martin Luther King Jr.)
  • “May the Force be with you.” (Star Wars)

General knowledge within a specific field

Basic concepts, theories, or methodologies that are widely accepted and taught within a particular discipline or area of study, such as:

  • The periodic table in chemistry.
  • The theory of supply and demand in economics.
  • The rules of grammar in linguistics.

Do I need a citation?

While the examples above provide a general idea of what constitutes common knowledge, determining whether a particular piece of information requires a citation can be challenging. To help writers navigate this decision, here are some guiding questions to consider:

Who is my reader, and what can I assume they know?

The determination of common knowledge depends heavily on the intended audience. Information that may be considered common knowledge for experts in a specific field might not be common knowledge for a general audience. 

When writing for a specialized audience, writers can assume a certain background knowledge and familiarity with the subject matter. However, when writing for a broader audience, writers should err on caution and provide citations for information that may not be widely known.

Could my reader dispute this statement?

If a reader could reasonably dispute a statement or claim, it is advisable to provide a citation. Common knowledge is generally accepted as factual and indisputable within a given context. If there is room for debate or disagreement, citing the source to support the claim is better.

Can my reader easily verify this statement across multiple sources?

Common knowledge is typically information easily verified across multiple reputable sources. If a statement or fact is obscure or difficult to confirm, it is recommended to cite the original source. This allows readers to verify the information and lends credibility to the writer’s work.

Common knowledge test

Here’s a common knowledge test to help determine whether a piece of information qualifies as common knowledge or requires citation:

  1. Is the information widely known and accepted within the given context or discipline?
    • If yes, it may be common knowledge.
    • If no, a citation is likely needed.
  2. Can the information be found in multiple reputable sources, such as textbooks, encyclopedias, or authoritative websites?
    • If yes, it may be common knowledge.
    • If no, a citation is likely needed.
  3. Is the information considered general knowledge or common sense within the target audience?
    • If yes, it may be common knowledge.
    • If no, a citation is likely needed.
  4. Is the information stable and unlikely to change over time?
    • If yes, it may be common knowledge.
    • If no, a citation is likely needed.
  5. Can the writer provide reliable sources to support the claim if the information is disputed or challenged?
    • If yes, a citation is needed to support the claim.
    • If no, the information should not be presented as fact.
  6. Is the information a well-known quotation, proverb, or saying?
    • If yes, it may be common knowledge.
    • If no, a citation is likely needed.
  7. Is the information a basic fact or concept widely taught and accepted within the field?
    • If yes, it may be common knowledge.
    • If no, a citation is likely needed.

To determine if a piece of information qualifies as common knowledge, apply this test. If the answer to most or all of these questions is “yes,” then the information can likely be considered common knowledge and may not require a citation. However, if the answer to any of these questions is “no,” provide a citation to support the information and maintain academic integrity.