Common knowledge refers to facts that are so widely known it is unnecessary to reference them. Common knowledge is general knowledge.
For example, the following points are common knowledge in New Zealand:
Beijing is the capital of China.
Wellington is the capital of New Zealand.
The Treaty of Waitangi was signed in 1840.
The Māori are the indigenous people of New Zealand.
These facts are so widely known that it is unnecessary to provide a source to support them.
Common knowledge may vary from country to country. In Argentina, for example, the signing date of the Treaty of Waitangi is not widely known.
Common knowledge may also vary from discipline to discipline. What is common knowledge in sociology, for example, may not be common knowledge in psychology. Some disciplines (such as in the sciences) incorporate facts into common knowledge faster than others. As you develop familiarity with a discipline you will become more aware of what is common knowledge and what is not.
Distinguishing common knowledge
Common knowledge can be identified by considering two important questions:
- Is the fact widely known?
- Is the fact disputed by anyone?
A widely known fact will appear in several different sources, particularly in general reference sources like encyclopædias or dictionaries. Common knowledge will also be widely known to your audience.
If there is academic disagreement about a fact it should not be treated as common knowledge. Likewise, interpretations of facts can be different between different sources, so the interpretation is not common knowledge.
Referencing common knowledge
Common knowledge does not need to be referenced. Most academic writing, however, does not focus on common knowledge. Instead, different interpretations and applications of facts and concepts are discussed, and these do need to be referenced appropriately.