What is defined as the closest documentary evidence to the subject being researched?

The concept of a primary source is critical in research as it refers to original materials that provide direct, firsthand evidence about the subject being studied. These sources are created by witnesses or first recorders of events at the time they occurred, making them invaluable for accurate historical understanding. Examples of primary sources include diaries, interviews, original research articles, photographs, and official documents. The direct nature of primary sources allows researchers to gain insights without the interpretation or bias that may come with secondary or tertiary sources.

In contrast, secondary sources analyze, interpret, or critique primary sources and are one step removed from the original material, while tertiary sources compile or summarize primary and secondary information, such as encyclopedias or databases. Moreover, reference sources serve as tools for finding information and generally do not contain original content but facilitate access to information from primary and secondary sources. This hierarchy underscores the importance of primary sources in establishing a direct connection to the research subject.