A 'primary source' is any piece of information that is used for constructing history as an artifact of its times. These often include works created by someone who witnessed first-hand or was part of the historical events that are being described, but can also include physical objects like coins, journal entries, letters, or newspaper articles. They can be, however, almost any form of information: advertisements from the 1950s can be primary sources in a work on perceptions of modern technology, for example.

What distinguishes a primary sources from a secondary source is how it is used more than what it actually contains as content. A secondary source is generally a historical description built up from primary sources, but historians often use secondary sources themselves as artifacts of their times (as such, primary sources) when attending to issues of historiography (for example, a book on the history of the computer might note that other books on the history of the computer ignore its military origins, or focus too much on its technical aspects).

A primary source is not, by default, more authorative or accurate than a secondary source. Secondary sources often are subjected to peer review, are well documented, and are often produced through institutions where methodological accuracy is important to the future of the author's career and reputation. A primary source like a journal entry, at best, only reflects one person's take on events, which may or may not be truthful, accurate, or complete. Historians subject both primary and secondary sources to a high level of scrutiny.

As a general rule, however, modern historians prefer to go back to primary sources, if available, as well as seeking new ones. Primary sources, whether accurate or not, offer new input into historical questions and most modern history revolves around heavy use of archives for the purpose of finding useful primary sources. A work on history is not likely to be taken seriously if it only cites secondary sources, as it does not indicate that original research has been done.

See also

• historiography
• secondary source
• tertiary source