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Common Knowledge & Attribution
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What is ‘common knowledge’?
Generally, common knowledge is information that someone finds undocumented in at least five credible sources. For example, writing is difficult,” is considered common knowledge in the field of composition studies because at least five credible sources can back the claim up.
Remember the golden rule: When in doubt, just cite.
If the citation proves unnecessary or unnecessarily repetitive your instructor or supervisor will inform you.
How do es cit ation work ? What is attribution?
Many professional organizations, including the Modern Language Association (MLA) and the American Psychological Association (APA), have lengthy guidelines for citing sources. We have resources to help you use these guidelines (linked on the sidebar to the left, just underneath this page). But many students are so worried about how to cite a particular source that they never learn how the citation system works. This is often why students end up accidentally plagiarizing.
Different citation styles have different rules. You should look at the rules for your own (not just the examples that show you how to cite a book chapter). But generally, here is how citation works:
There are three elements: signal phrase (also called “signposting”), in-text citation (also called “parenthetical citation”) , bibliographic citation.
- A signal phrase is something like “According to Chen Li...”
- An in-text citation will look like (Li, 2020) or (Li 7)
- A bibliographic citation will look like: Li, C. (2020). Best practices to avoid plagiarism. Journal of Basic Writing, 42 (1), pp. 4-12.
The signal phrase and the in-text citation show up in the sentences of your paper. The bibliographic citation shows up in the references/works cited/bibliography at the end of your paper, or possibly footnotes at the bottom of each page. You need all three to effectively attribute ideas and words to their proper sources of origin.
The signal phrase and the in-text citation work together. The signal phrase shows up when you first start talking about a source. It says to the reader “hey! I am drawing on someone else’s idea.” You might use more than one signal phrase if you talk about a source for a few sentences or throughout a paragraph. Then, when you are done talking about that source, the in-text citation ends the sentence. It says to the reader “hey! This is the end of me talking about this source for now. Here is the information you will need to go to the bibliography and find the source I’m talking about.” The bibliographic citation then provides all the information the reader needs to go find the source you looked at. It also tells the reader a number of things before they even do that: the author, how current the source is, its title, and where it was published (like an academic journal, a news site, or a book with lots of chapters).
Here's an example of what all that looks like put together, using APA:
In this example, I opened with a signal phrase that included the author’s name and the year, to tell my reader who I am citing from. Then I summarized Li’s point in the rest of the first sentence. The second sentence includes paraphrase, where I restated her ideas in my own words, and a direct quote in quotation marks, where I used her words exactly. The in-text citation only includes the page number in this case, because I just gave the rest of the citational material a few words earlier. I could have also written (Li, 2020, pg. 7) and that would have been correct. Then I gave all the information about this (made-up) journal article in my references.
Look at some articles in a journal in your field — maybe class readings, or sources for your own research project. Pay attention to how the authors attribute sources. Look for signal phrases, in-text citations, and bibliographic citations, and try to see the patterns in how these authors use them. Each field is different — this is just one example.
See also our resource on quoting, paraphrasing, and summarizing. You can’t cite appropriately if you are not sure exactly how you are using source material.
Citing Your Sources
What you don't need to cite.
- Taking notes
- Using direct quotation
- Paraphrasing or summarizing
- Citation Guides, Manuals, Resources
You do NOT need to cite:
- your own words, ideas and original research
- facts that are found in many sources (ex: Marie Antoinette was guillotined in 1793.)
- things that are easily observed (ex: Many people talk on cellphones while driving.)
- common sayings (ex: Every man has his price.)
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A publication of the harvard college writing program.
Harvard Guide to Using Sources
- The Honor Code
The Exception: Common Knowledge
The only source material that you can use in an essay without attribution is material that is considered common knowledge and is therefore not attributable to one source. Common knowledge is information generally known to an educated reader, such as widely known facts and dates, and, more rarely, ideas or language. Facts, ideas, and language that are distinct and unique products of a particular individual's work do not count as common knowledge and must always be cited. Figuring out whether something is common knowledge can be tricky, and it's always better to cite a source if you're not sure whether the information or idea is common knowledge. If you err on the side of caution, the worst outcome would be that an instructor would tell you that you didn't need to cite; if you don't cite, you could end up with a larger problem.
If you have encountered the information in multiple sources but still think you should cite it, cite the source you used that you think is most reliable, or the one that has shaped your thinking the most.
Categories of Common Knowledge
Widely known facts
Widely known scientific and historical facts—such as the molecular structure of water (H2O), or that Andrew Jackson was the seventh president of the United States—generally count as common knowledge. You can include such facts in your writing without citation and without fear of committing plagiarism. Other facts that count as common knowledge—for instance, that Franz Boas, the distinguished American ethnologist, held the first academic appointment in anthropology in the United States—are widely known to some groups of people (professional anthropologists) but perhaps not to you. Nevertheless, you would not have to cite the fact about Boas, since it is common knowledge in the sense that no particular individual discovered this information (say, through archival research at Columbia University, where Boas taught). On the other hand, as soon as your discussion becomes more specific and puts forth assertions that would be the product of an individual's thought, research, or analysis, you do have to cite. For example, if you read Anthony Abraham Jack's The Privileged Poor and then wrote about the conclusions he drew from his study of economically disadvantaged students at elite colleges, you would need to cite his work.
Ideas or interpretations are usually not considered common knowledge, unless they are very widely held.
Ideas or interpretations generally do not count as common knowledge. If you read in R.A.C. Parker's history of World War II that British Prime Minister Neville Chamberlain did not have to agree to the 1938 Munich Pact with Hitler, and that he could have chosen an alternate path, you would need to acknowledge the source, since this judgment is Parker's theory rather than a widely agreed upon fact. (Historians disagree on the factors that led Chamberlain to agree to sign on to the Munich Pact.) Some interpretations or opinions (rather than facts) have entered the realm of common knowledge and need not be cited. If you were to introduce the claim that culture provides a means by which humans adapt to their environments, you would not need to cite a source for this claim, since it is almost universally held by anthropologists. But, if you were unsure that this was the consensus view among anthropologists, you would be best served simply to cite the source. On the whole, opinions or interpretations do not enter the realm of common knowledge as easily as historical or scientific facts.
Verbatim language drawn from a source is rarely common knowledge, unless the formulation is widely known.
You must always provide a citation for quotations you use in your writing. The only—and rare—exceptions to this rule concern well-known quotations that have entered the realm of common knowledge. For example, if you were writing a paper about President Obama's Inaugural Address, you would need to cite your source for any quotations you used from the speech. However, if in the course of that paper you compared one of President Obama's lines to this very well-known phrase from John F. Kennedy's Inaugural Address, "Ask not what your country can do for you—ask what you can do for your country," you would not need to provide a citation for that one phrase. However, if you were to analyze Kennedy's speech substantively and quote additional lines, then you would need to cite anything you quoted from his speech so that your readers could confirm the original language of the speech. If you are not sure whether a quotation is common knowledge, cite it.
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