Research and Citations Center
Types of Sources
What kinds of evidence can you use, and what are the problems with them?
- Primary sources are documents and artifacts that come from the time and place being investigated and so provide first-hand testimony.
- Secondary sources are where a scholar writes about and interprets primary sources, drawing conclusions about what they tell us about the time and place they come from. Secondary sources include scholarly books that use primary sources and articles in peer-reviewed academic journals.
- Tertiary sources involve writers bringing together secondary sources and averaging them out to make general statements about history.
Primary sources are great because they give us direct access to what we’re writing about. But you must remember that they are not the truth and must not be taken at face value.
Primary sources are always distorted by intentional bias (the author wants to convince you of something); unintentional bias (the author’s writing is shaped by his or her culture and upbringing); point of view (the author only knows what he or she actually saw); translation (all ancient sources were written in another language unlike English, so the content is always altered by translation); survival (only some documents survive from the ancient world, and some of them were deliberately selected to survive in the intervening centuries while others were not, skewing out evidence pool). You must always ask what idea the author was trying to convince you of in writing the work at hand.
If the events themselves are “level zero”, primary sources (“level one”) are a full layer of distortion away from the truth. Because of bias and point of view, there is always this layer of distortion in all primary sources. All primary source evidence is skewed and we cannot know the pure truth. There are no facts in history. Consequently, primary source evidence must always be unpacked for bias and other distortions.
Secondary sources are valuable because they provide both expert testimony and useful contextualization not always present in primary sources. But secondary sources are, by their nature, interpretations. They are the subjective conclusions of a particular researcher, and history works by historians looking at the same evidence and positing different and often conflicting interpretations until there is a general agreement (which in many cases does not happen, especially in ancient history where there’s less evidence to examine). They are not the truth either; they are informed opinion. Secondary evidence adds a layer of interpretation to events, distancing them even further from events than primary sources.
These include textbooks, encyclopedias, dictionaries, and most web sites (excluding peer-reviewed journals and transcriptions of primary sources). Also banned are “reference entries” (these generally come from encyclopedias) and reviews, which involve a scholar talking about a secondary source (and which is therefore tertiary). You want the secondary source itself, not a review.
Tertiary sources are not allowed under any circumstances, and you will be strongly penalized for citing tertiary sources in any paper for a history course. The level of distortion, away from the testimony of primary sources and the nuanced arguments of secondary sources, is too great.