Secondary Sources: The Historian's Toolkit
What Makes a Source "Secondary"?
The core idea is distance. A secondary source is at least one step removed from the event, person, or period it discusses. The author was not present, did not participate, and did not create the original evidence. Instead, they gather multiple pieces of primary evidence (like letters, photographs, or government records) and use them to construct an explanation or tell a story about what happened and why.
Imagine you are trying to understand a major school event, like a championship game, a year after it happened. You weren't there. To learn about it, you might:
- Read the school newspaper's feature article reviewing the season.
- Watch a documentary made by a student club about the team's journey.
- Listen to a podcast where two teachers debate the key plays.
All of these are secondary sources. They are created after the fact by people analyzing the primary sources: the game footage, the scoreboard, the players' own social media posts, and interviews with coaches.
Primary vs. Secondary: A Crucial Partnership
Primary and secondary sources work together. You cannot have a reliable secondary source without primary sources, and primary sources often need the context and explanation provided by secondary sources to be fully understood.
| Feature | Primary Source | Secondary Source |
|---|---|---|
| Creation Time | Created at the time of the event or very soon after. | Created later, often years or centuries after. |
| Creator's Role | An eyewitness, participant, or first recorder. | A scholar, historian, or analyst who was not present. |
| Content | Raw, unfiltered evidence. (e.g., data, diary entry, speech). | Interpretation, synthesis, and analysis of evidence. |
| Purpose | To record, communicate, or express at the moment. | To explain, argue a point, or provide context. |
| Example (American Revolution) | The Declaration of Independence (1776). | A 2020 biography of George Washington. |
| Example (Science) | Marie Curie's laboratory notebook (1898). | A textbook chapter on the discovery of radioactivity. |
The Many Forms of Secondary Sources
Secondary sources come in many shapes and sizes, tailored for different audiences and purposes. Recognizing them is a key research skill.
For Students and the Public: These are designed to inform and educate a broad audience.
- Textbooks: Your history or science textbook is a classic secondary source. It compiles information from countless primary sources and other scholars' works into a structured, curriculum-friendly format.
- Documentaries and Educational Films: A film about World War II uses primary footage, photographs, and interviews, but the narration provides the interpretation, connecting the pieces into a story.
- Museum Exhibit Labels: The artifact is primary; the text explaining its significance and historical context is secondary.
- Articles in Popular Magazines: A National Geographic article about ancient Egypt synthesizes the latest archaeological findings for general readers.
For Scholars and Researchers: These sources present original arguments and contribute to academic debate.
- Academic Books (Monographs): A detailed, book-length study by a historian on a specific topic, like the economic causes of the Civil War.
- Scholarly Journal Articles: These are peer-reviewed1 papers where historians present new research and interpretations, often quite focused (e.g., "Re-examining the Role of Women in the Scientific Revolution").
- Literature Reviews: A specialized type of secondary source that summarizes and evaluates the current state of research on a particular topic, showing how interpretations have changed over time.
- Biographies: A detailed account of a person's life, built from primary sources like letters and diaries, but shaped by the biographer's perspective and analysis.
A Scientific Case Study: Understanding the Atom
Let's trace how our understanding of a scientific concept evolves through primary and secondary sources. Consider the model of the atom.
Primary Sources (The Raw Discoveries):
- J.J. Thomson's 1897 paper announcing the discovery of the electron. It contains his experimental data and his "plum pudding" model. The formula for the charge-to-mass ratio of the electron, $e/m_e$, was derived here.
- Ernest Rutherford's 1911 paper describing the gold foil experiment, with data showing that most alpha particles passed through, but some were deflected sharply. This was the primary evidence for a dense, central nucleus.
- Niels Bohr's 1913 trilogy of papers proposing his quantum model of the atom, introducing quantized electron orbits. The formula for the energy of an electron in a hydrogen atom, $E_n = -13.6 / n^2$ eV, was a key result.
Secondary Sources (The Analysis and Synthesis):
- A 1915 chemistry textbook explaining the new "nuclear model" of the atom to students, comparing Thomson's and Rutherford's work.
- A 1947 scholarly article titled "Fifty Years of Atomic Theory," reviewing the progression from Dalton to Bohr and beyond.
- A modern high school physics textbook chapter that presents the historical models (Thomson, Rutherford, Bohr) as steps toward the modern quantum mechanical model, using diagrams and simplified explanations.
- A 2010 documentary "The Atom" featuring historians of science and physicists discussing how these discoveries revolutionized our world.
The secondary sources take the complex, technical primary papers and make them understandable. They connect the dots, showing how one experiment led to a new model, which was then refined by another. They provide the story of scientific progress.
How to Evaluate a Secondary Source
Not all secondary sources are equally reliable. When you use one, you should ask critical questions.
| Question to Ask | Why It Matters |
|---|---|
| Who is the author? What are their credentials? | An expert historian or scientist is more likely to provide accurate, well-researched analysis than a blogger with no background. |
| When was it published? | Newer sources may include recent discoveries or updated interpretations. Older sources can show you how people thought in the past. |
| Who is the publisher? (e.g., university press, popular magazine) | Academic publishers use peer review, which helps ensure quality. Popular publishers may prioritize engaging storytelling over strict accuracy. |
| Does it cite its sources? Is there a bibliography or footnotes? | This is crucial. It shows the author has done their homework and allows you to check the primary sources yourself. A source without citations is harder to trust. |
| What is the author's perspective or bias? | Every historian has a point of view. A source should acknowledge different interpretations and support its claims with evidence, not just opinion. |
Important Questions
Q: Can a source be both primary and secondary?
Yes, depending on the research question. A history textbook from 1955 is a secondary source for learning about the American Revolution. But for a historian studying how the Civil Rights Movement was taught in the mid-20th century, that same 1955 textbook becomes a primary source. It is a firsthand artifact of the social attitudes and educational practices of its time. The classification depends entirely on how you are using the source.
Q: Why can't I just use secondary sources for my research project?
You can and often will start with secondary sources! They are essential for getting an overview, understanding the key debates, and finding clues about which primary sources to examine. However, relying solely on them means you are only seeing history through someone else's lens. To form your own interpretation or to check the validity of an author's claim, you need to consult the primary evidence. Good research is a conversation between primary and secondary sources.
Q: Are Wikipedia and other encyclopedias secondary sources?
Yes, they are tertiary sources2. They are one step further removed. Encyclopedias like Wikipedia typically compile and summarize information from secondary (and sometimes primary) sources. They are excellent for getting a quick, general overview of a topic. However, for serious academic work, you should use them as a starting point to find the secondary and primary sources listed in their references and footnotes, which you can then evaluate directly.
Footnote
1 Peer-reviewed: A process where other experts in the same field (peers) evaluate a scholarly work before it is published to ensure it meets standards of quality, accuracy, and originality.
2 Tertiary Source: A source that compiles, distills, or indexes primary and secondary sources. Its main purpose is to provide a quick, condensed overview of a topic with few original ideas. Examples include encyclopedias, almanacs, and most textbooks at the K-12 level.