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Identifying & Using Scholarly Sources

Best practices for selecting authoritative scholarly sources for your research needs.

What are Primary, Secondary & Tertiary Sources

When doing research for a theological essay or paper, primary sources are critical. Primary sources provide the direct and original evidence for the thoughts, beliefs, and ideas during a particular time period, during a particular event, or of a particular person or group of people. In theological writing, these original artifacts include both physical and digital copies of original works.


Primary sources are the artifacts that “provide direct evidence of human activity” (Guidelines for Primary Source Literacy, 2018). As a reader, a writer, or a researcher, it is not uncommon to find the use of primary sources challenging. This challenge comes from the critical analysis that we are required to perform when analyzing the source. Proper analysis requires that we pay attention to the often unique and sometimes unfamiliar context in which the source was written. According to the American Library Association (ALA), primary sources “require critical analysis due to their creators’ intents and biases; the variety of context in which they have been created, preserved, and made accessible; and the gaps, absences and silences that may exist in the material” (Guidelines).

Primary sources provide original evidence of: 
  • A time period
  • An event
  • A work
  • A people
  • An idea
Examples of theological primary sources include, but are not limited to:
  • Summa Theologica
  • Dead Sea Scrolls
  • Original Writings of Saints
  • Apostolic Constitutions and Papal Encyclicals
  • Preserved Documents from Councils

Where to find Primary Sources 

Below is a small selection of primary sources that can be found in the CDU Online Library. Please contact the librarian on how to locate the primary sources specific to your writing needs.

Secondary sources are works that analyze, assess, or interpret a historical event, era, or phenomenon. Secondary sources often offer a review or critique of a Primary source. Secondary sources are generally written well after the advent of the Primary source.

Secondary sources do not offer new evidence.

Examples of Secondary sources include academic books, journal articles, reviews, conference proceedings, dissertations, and class lectures.

Where to find Secondary sources in the CDU Online Library

Tertiary sources index, organize, or compile other sources.

Examples of Tertiary sources include dictionaries, encyclopedias, almanacs, fact books, Wikipedia, bibliographies, directories, guidebooks, manuals, handbooks, and textbooks.

Note: Depending on the content, dictionaries, encyclopedias, bibliographies, and textbooks may also be Secondary sources.