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Common Knowledge

How Do I Know if It's Common Knowledge?

"Common knowledge" refers to facts or information so readily available, it cannot be said to have a single author or researcher. Common knowledge exceeds the limits of "what everybody knows," but it isn't writing or research that can be attributed to an original source. For example, William Shakespeare's birthday is considered common knowledge, even though not many people know it by heart. The information could be found commonly, without a single source of publication. Metric conversions, the periodic table, birthplaces of famous people, and significant dates in history are all examples of common knowledge. The Internet has muddied the issue of what is common knowledge even further because so much of what is on the Internet is plagiarized itself! Finding information undocumented on the Web does not mean it is common knowledge.

If you aren't sure whether or not the information you are using is common knowledge-document it. It is always better to be safe than sorry. With time, experience, and education, this distinction will grow more clear.

Here's how Bonnie Tensen, author of Research Strategies for a Digital Age, explains it:

However, determining what should be considered "common knowledge" can be a tricky task. Material is normally considered common knowledge if it's something most people already know or could easily be found in a general reference source. For example, Ronald Reagan's birthday (February 6, 1911), the number of stomachs a cow has (four), the capital of Malaysia (Kuala Lampur), or the Aaron Copland composition that includes a Shaker hymn (Appalachian Spring) are all examples of common knowledge. But what is considered common knowledge can vary according to audience (since it is based on what you assume your reader will already know or be able to access quickly).  Age, profession, and level of education are all variables that can affect your decision to document a fact or not. Most professors would agree that if you can find the information undocumented in several different sources, it is probably common knowledge. (Be careful--the cut-and-paste nature of the Web has resulted in incredible abuse of intellectual property. The judgment of Web authors should not serve as a guide to your own decision regarding what is common knowledge.) Most instructors would encourage you to err on the side of caution. In other words, if you are unsure whether something is common knowledge, it is better to go ahead and document it.

Examples of Common Knowledge:
  • On September 11, 2001, New York City and Washington D.C. suffered terrorist attacks.

  • The courts convicted Lee Harvey Oswald for the assassination of President John F. Kennedy.

  • Rupurt Murdoch owns many media corporations.

  • World War I began in 1914.

  • The speed of light is 3 X 10E8 meters per second.
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