How to read history: primary and secondary sources, and why interpretations differ

Primary and secondary sources

A primary source is material left by someone who lived through or closely witnessed the period in question. Government documents, letters, diaries, inscriptions, newspapers of the day, artefacts and buildings all count. A secondary source is a later study, textbook or explanation that gathers and analyses primary sources. Primary sources are vivid but fragmentary; secondary sources are organised but carry the author's interpretation. Rather than one being better, the basic practice is to use both to check each other. For beginners, the easiest route is to get the overall frame from a textbook or survey, then follow the primary sources that book relies on wherever a passage makes you curious.

The same document changes with the question

Whether something is primary or secondary depends on what you are asking. The Samguk Sagi was compiled in 1145 by Kim Bu-sik and others in the Goryeo period, so for the Three Kingdoms it is a record assembled centuries later. But if you ask how people in mid-Goryeo saw their past, the same book becomes a primary source produced by that very period. When you look at any source, it helps to note both when it was made and which period you are asking about.

Five questions to ask a source

A source is not an answer to copy down but testimony to question. When you meet an unfamiliar record, work through the questions below in order. Even if you cannot answer them all, asking them changes the way you read.

• Who left it: what was their position and point of view
• When was it made: right after the event or long afterwards
• Who was it meant for: a king, an office, descendants, the writer alone
• What is missing: which people and events go unmentioned
• Does it match other sources: do independent records agree

Only what survives remains

The sources we can see are only a fraction of what was produced. Much was lost to war and fire, and only a minority could write in the first place. Records of royal courts, government offices and scholars survive in relative abundance, while the voices of farmers, women and enslaved people are rare. The absence of records does not mean those lives did not exist. This is why recent research turns to everyday objects, household registers and lawsuit documents to fill the gaps. Be careful not to mistake the viewpoint of the groups with the most records for the picture of the whole era.

Why interpretations differ

There are three main reasons interpretations of the same event diverge. New sources may come to light and revise earlier accounts; researchers may ask different questions about politics, economy or daily life; and the same facts may be judged by different values. Having several interpretations, however, does not mean anything goes. A claim that contradicts the sources or cannot show its evidence is not an interpretation; it is simply wrong.

Choosing good secondary sources

When picking a book or article, looking at its form before its content tells you a lot about reliability. Check whether the author has researched the field, whether each claim is sourced, whether opposing views are presented and answered, and when the work was published. An older book may not reflect later excavations and research. For something online, first see whether it cites original sources or scholarly work, or whether it simply repeats another blog.

Frequent mistakes

The most common mistake is judging people of the past by today's standards and common sense. They made choices under the conditions of their time without knowing the outcomes we know. Other frequent mistakes include the following.

• Drawing a conclusion from a single source
• Trusting a quotation of a quotation without checking the original
• Assuming the cause was obvious once you know the result
• Stretching one local case to cover the whole country

Practice for yourself

The best exercise is to read two books on the same event side by side and make a table of where their explanations part ways and what evidence each one offers. The Annals of the Joseon Dynasty have been made available online in the original and in modern Korean translation by Korea's national history committee, so picking one event from a textbook and finding it in the Annals is a rewarding experience. Even in translation you can sense whose eyes the record was written through.