Primary Source - Classifying Sources

Classifying Sources

Many sources can be considered either primary and secondary, depending on the context in which they are examined. Moreover, the distinction between primary and secondary sources is subjective and contextual, so that precise definitions are difficult to make. Investigative journalism, for example, is a primary source of information. A book review, when it contains the opinion of the reviewer about the book rather than a summary of the book, becomes a primary source.

If a historical text discusses old documents to derive a new historical conclusion, it is considered to be a primary source for the new conclusion. Examples in which a source can be both primary and secondary include an obituary or a survey of several volumes of a journal counting the frequency of articles on a certain topic.

Whether a source is regarded as primary or secondary in a given context may change, depending upon the present state of knowledge within the field. For example, if a document refers to the contents of a previous but undiscovered letter, that document may be considered "primary", since it is the closest known thing to an original source; but if the letter is later found, it may then be considered "secondary"

In some instances, the reason for identifying a text as the "primary source" may devolve from the fact that no copy of the original source material exists, or that it is the oldest extant source for the information cited. Alternatively, when a printed version of a document is made from an electronic version, the electronic version may be termed the primary document.

Whether a source is primary also depends on its age. For example, encyclopedias are generally considered tertiary sources, but Pliny's Naturalis Historia, originally published in the 1st century, is a primary source for information about the Roman era.