Comparing and Combining Multiple Sources

Categorizing Sources: Primary, Secondary, and Tertiary

When examining written texts, researchers categorize materials based on their relationship to the original event or topic. A primary source provides direct, firsthand evidence about an event, object, person, or work of art. These materials offer original evidence from the period under study or present firsthand accounts from participants or witnesses, even when those accounts are composed years later. Common examples include diaries, letters, personal journals, and firsthand memoirs. Autobiographies serve as primary sources because they are written by the individuals who lived the experiences. In science and governance, raw research data, reports of original clinical trials, laboratory notes, and official government records, such as birth certificates, court transcripts, and legislative acts, also function as primary sources. In addition, physical artifacts like tools, historic clothing, pottery, and ruins, alongside eyewitness photographs, original audio recordings, speeches, and live video footage, are primary sources.

A secondary source interprets, analyzes, critiques, or summarizes primary sources. Secondary sources interpret, analyze, or summarize original evidence, but they need not be written after an event or by someone who did not witness it. Biographies generally serve as secondary sources when their authors interpret evidence about another person's life, but a biographer may also draw on firsthand experience, and a biography's classification depends on the research question. Common examples include standard history textbooks, literary review articles, and scholarly critiques that interpret novels, poems, or artwork. Similarly, documentaries that synthesize historical footage with modern scholarly commentary are generally classified as secondary sources.

Tertiary sources serve a different function by compiling, indexing, or organizing primary and secondary source materials. Examples include encyclopedias, almanacs, bibliographies, and directory databases. Notably, a source's classification as primary or secondary depends on the specific research question being asked. For instance, an old textbook functions as a secondary source if you are investigating the historical events described within its chapters, but it becomes a primary source if you are studying educational history and curriculum design of that era.