Primary and Secondary Sources: What’s the Difference?

In this short post, I would like to address a foundational question in historical practice: what is the difference between primary and secondary sources? If you haven’t heard those terms before, I am going to boil them down for you.

First of all, let’s talk about how do we know anything about the past? How do we know that Wellington defeated Napoleon at the Battle of Waterloo on June 18, 1815, or that the Roman Empire reached from the Middle East in the East to Spain in the West, from Britain in the North to North Africa in the South? How do we know that the Berlin Wall fell in 1989? How do we know anything about the past at all? Well, we know about it by hearing from the people who were there who lived it.

But, you say, there’s a problem! Most of the people who lived in the past are dead, so we can’t talk to them. Indeed, that is a problem. We may not have the people themselves, but we do have what they left behind. Things like letters, diaries, ships log books, newspapers, war records, political records, birth certificates, marriage certificates, and so on, are all left behind from the past and give us valuable information about the people who lived at the time that these records were produced.

The records that are left behind from a certain time-period, and if that is the time-period that is being studied, we call these records ‘primary sources’.

The Peloponnesian War by Thucydides, is an example of a primary source. Thucydides was a Greek historian who lived in ancient Athens in the 5th century BC and he wrote a book about events that were happening in his own time, that is, the Peloponnesian War between the city-states of Athens and Sparta, from the Athenian perspective. We still have his book, you can buy a Penguin Classics edition from Amazon. His book is a primary source because he is writing about events that happened in his own time that he himself experienced and lived through. Sadly, we can’t talk to him directly, but we can read and study his book which is an invaluable source to historians.

What if someone is writing about events that happened before they were born, say 100, 200, 500, 1000 years after it happened? An example of this type of source is The Rise and Fall of Athens by one of the last Greek historians named Plutarch (it’s part of Plutarch’s Lives but you can also buy it as a separate book). Athens was at its height in the 5th century BC and Plutarch was writing in the 1st century AD. That’s around 600 years later, from now back to the Wars of the Roses! So clearly Plutarch wasn’t around to experience and live through the events or meet the people he wrote about. He would have gotten information for his book from other sources, and probably would have had access to primary sources that we no longer have. Therefore, we call his work a ‘secondary source’.

So in review, a primary source is written or created by someone who lived through the events it is describing. A secondary source, on the other hand, is written many years after the events described or the death of the person written about.

What sources would be more reliable if we we want to get accurate information about the past? Primary sources are generally more reliable because they were produced closer to the time that is being studied. The general rule of thumb is: the closer the source is to the period, person, or event, the more likely it is to be accurate.

I just want to add a quick comment on archaeological artefacts, like pottery, spearheads, beads, and so on. These are primary sources because, again, they were made at the time.

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