Secondary sources

In scholarship, a secondary source is a document or recording that relates or discusses information originally presented elsewhere. A secondary source contrasts with a primary source, which is an original source of the information being discussed. Secondary sources involve generalization, analysis, synthesis, interpretation, or evaluation of the original information. Primary and secondary are relative terms, and some sources may be classified as primary or secondary, depending on how it is used. An even higher level, the tertiary source, resembles a secondary source in that it contains analysis, but attempts to provide a broad overview of a topic that is accessible to newcomers.

Classification
Many sources can be considered either primary or secondary, depending on the context in which they are used. Moreover, the distinction between primary and secondary sources is subjective and contextual, so that precise definitions are difficult to make. For example, 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, but a secondary source of information found in the old documents. Other 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".

Attempts to map or model scientific and scholarly communication need the concepts of primary, secondary and further "levels". One such model is the UNISIST model of information dissemination. Within such a model these concepts are defined in relation to each other, and the acceptance of this way of defining the concepts are connected to the acceptance of the model.

Other languages, like German, call the secondary sources Sekundärliteratur, leaving Sekundärquelle to historiography. A Sekundärquelle is a source that can tell about a (lost) Primärquelle, e.g. a letter is quoting from minutes that no longer exist and can not be consulted by the historian.

In science and medicine
In the sciences, a review article, book review, or meta-analysis are both examples of a secondary source. Some academic journals only publish reviews. Unlike in the humanities, scientific and medical peer reviewed sources are not generally considered secondary unless they are a review or a meta-analysis. Some scientific document search engines such as PubMed allow you to limit your searches to reviews and meta-analyses. Secondary sources can help trace the history of scientific and mathematical ideas, including who is credited as the original source of the idea.

A survey of previous work in the field in a primary peer-reviewed source is secondary. This vastly increases the amount of secondary source information available when there are few reviews in a field.

Library and information science
In library and information sciences, secondary sources are generally regarded as those sources that summarize or add commentary to primary sources in the context of the particular information or idea under study.

Mathematics
An important use of secondary sources in the field of mathematics has been to make difficult mathematical ideas and proofs from primary sources more accessible to the public; in other sciences tertiary sources are expected to fulfill the introductory role.

In humanities and history
Primary sources are those closest to an event, such as diaries and first-hand newspaper and magazine accounts. In the humanities, unlike the sciences and medicine, secondary sources in history and humanities are usually newspaper, magazine, academic journal, or other written accounts from the perspective of a different person than the person who experienced the event. In the humanities, a peer reviewed article is always a secondary source, but isn't necessarily secondary in the sciences.

Medicine presents a special case because it is one of the few sciences which is also a humanity; linguistics is another example. Those disciplines are treated as sciences, not humanities.

The delineation of sources as primary and secondary first arose in the field of historiography, as historians attempted to identify and classify the sources of historical writing. In scholarly writing, an important objective of classifying sources is to determine the independence and reliability of sources. In contexts such as historical writing, it is almost always advisable to use primary sources if possible, and that "if none are available, it is only with great caution that [the author] may proceed to make use of secondary sources." Many scholars have commented on the difficulty in producing secondary source narratives from the "raw data" which makes up the past. Historian/philosopher Hayden White has written extensively on the ways in which the rhetorical strategies by which historians construct narratives about the past, and what sorts of assumptions about time, history, and events are embedded in the very structure of the historical narrative. In any case, the question of the exact relation between "historical facts" and the content of "written history" has been a topic of discussion among historians since at least the nineteenth century, when much of the modern profession of history came into being.

As a general rule, modern historians prefer to go back to primary sources, if available, as well as seeking new ones, because 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. On the other hand, most undergraduate research projects are limited to secondary source material.

Law
In the legal field, source classification is important because the persuasiveness of a source usually depends upon its history. Primary sources may include cases, constitutions, statutes, administrative regulations, and other sources of binding legal authority, while secondary legal sources may include books, articles, and encyclopedias. Legal writers usually prefer to cite primary sources because only primary sources are authoritative and precedential, while secondary sources are only persuasive at best.

Family history
"A secondary source is a record or statement of an event or circumstance made by a non-eyewitness or by someone not closely connected with the event or circumstances, recorded or stated verbally either at or sometime after the event, or by an eye-witness at a time after the event when the fallibility of memory is an important factor." Consequently, according to this definition, a first hand account written long after the event "when the fallibility of memory is an important factor" is a secondary source, even though it may be the first published description of that event.

Autobiographies
An autobiography can be a secondary source in history or the humanities when used for information about topics other than its subject. For example, many first hand accounts of events in World War I written in the post-war years were influenced by the then prevailing perception of the war which was significantly different from contemporary opinion.