Sources: primary, secondary, and tertiary

Everyone does research, because everyone looks for information at some time or another.

Wherever anyone finds information is, of course, a source. Whenever we find a source, it follows that someone wrote it or spoke it into some kind or recording devise or is otherwise responsible for the fact that it exists.

There are three general kinds of sources: primary, secondary, and tertiary. These terms mean something a little different from one discipline to another.

The distinction is ordinarily introduced in order to prepare college students, and especially graduate students, to write term papers, theses, and dissertations. It is useful for anyone to know for any kind of research, including satisfying personal curiosity about something.

Primary sources

A primary source comes straight from the horse’s mouth, so to speak. Primary sources in the sciences comprise scientific papers in professional journals. That is, the authors describe their research and findings.

In law, primary sources are the exact wording of statutes, regulations and court decisions. In art, they are the paintings, sculptures, etc. of a particular artist.

In any kind of historical research, an eyewitness account of an event would be a primary source. A transcript of a speech would be a primary source. For any event that anyone might want to study, the primary sources would be about the same age.

That doesn’t necessarily mean exactly the same age. Living veterans of the Second World War are in their 80s or older, and if anyone of them commit their memories to writing or get interviewed for an oral history project, their works become primary sources that someone later can study.

Once the last of them has passed, no new primary sources about the war will be possible.

Primary sources can be very difficult to find. If there is only one copy of something in the world, obviously only a serious scholar is going to track it down and go consult it.

With scientific papers, the problem is not so much finding them, but understanding them and their implications.

A single primary source by itself often isn’t very helpful.

Secondary sources

Secondary sources make up most of what we read.

The author of a Scientific America article did not perform the research that the article reports. He or she read the papers and perhaps interviewed the scientists. Combining scientific knowledge with the writing skills necessary to explain technical details that ordinary readers can understand, the author has made information accessible to people who would not ordinarily be able to understand it.

The author of a history book has examined lots of primary sources, and lots of secondary sources as well, to put together an overview of events and their significance.

Remember that whatever happened yesterday is history. A book or article about the most current of events is every bit a work of history as a book or article about something that happened centuries ago.

Secondary sources are one step removed from primary sources because the author has drawn the account from various other sources.

Also, secondary sources interpret the information the author found. Every discipline has its fashions. In any ten or fifteen year period, authors on any given subject might be in substantial agreement, but then someone will offer a new interpretation.

Generally speaking, anything significantly based on primary sources will be more reliable than writings based entirely on other secondary sources.

Tertiary sources

Encyclopedias, annotated bibliographies, abstracts, dictionaries, etc. that summarize the secondary literature are called tertiary sources.

Everyone’s first exposure to research probably came through the encyclopedias we studied for the papers we wrote in third grade or so. Once we got to high school and college, teachers told us to stop using them as sources and learn to use secondary sources or even some primary sources.

School children use tertiary sources written to be used by children. Older students and adults still need encyclopedias, even though they are seldom suitable sources when writing papers.

There are general encyclopedias like Encyclopaedia Britannica. There are lots of more specialized encyclopedias devoted to, say, chemistry and all of its various subspecialties. Nowadays, of course, we can all find Wikipedia online and have less need to consult print encyclopedias.

When we’re not writing a paper to turn in or submit for publication, an encyclopedia may have all the information about something that we need. I use Wikipedia for checking dates, titles, etc. all the time.

Choosing sources

So a primary source is as close to a particular event as anyone can get. A secondary source is a later interpretation of the event. A tertiary source is a general summary of information contained in secondary sources.

Each kind of source is farther away from the event described. The distinctions among these three levels of sources may seem clear enough. Deciding which category any given source belongs to may be more difficult.

Also, the three-part categorization does not mean that each kind of source is somehow progressively less reliable. A primary source can be the product of someone interested in making himself look good or someone else look bad. It can even be an outright fabrication or falsehood. Perhaps it is the author of a secondary source that proves it to be a lie.

When you need information, the kind of source you need to look at depends on how much information you need and what you intend to do with it.

The other day I came across “lance de fer” in an article I was reading. I walked across the room to the Encyclopaedia Britannica set I bought in 1976 to find out what it was.

That particular poisonous snake has not become anything different in the last 35 years. The article about it in my ancient encyclopedia could not mislead me, but if I really cared to know enough about the lance de fer to write about it, (or prepare to trek through the jungles where it lives) I would have to study several secondary sources.

Photo credit: Ocean City public information booth. Some rights reserved by (Link no longer works as of June 2017.)

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