Types of Evidence

To support their central claim and subclaims, authors use a variety of types of evidence and explain to their readers how the evidence supports the claim. Following are a few types of evidence.

Exhibits

Shakespeare’s Sonnet 18, which might serve as an exhibit in a text

Exhibits are examples or excerpts from the object of study. Humanities (like English or religious studies) makes use of exhibits in the form of primary texts. For example, an article about Shakespeare’s sonnets would quote small sections of the poems. A text about Buddhism might quote English translations of the sutras (and perhaps the Sanskrit originals).

Exhibits can also include visual reproductions. A paper on Michelangelo might attach images of the paintings in the Sistine Chapel. A book about the Great Depression might use reproductions of photographs by the WPA. A study of the Jurassic period might provide photographs of dinosaur bones and excavation sites.

Examples or observed phenomenon can also be exhibit sources.  Social media scholars might use an Instagram post as an exhibit source, or political scientists might refer to a piece of legislation.  By themselves, exhibits are not evidence; however, when the author explains how an exhibit supports a reason, it becomes evidence.

Expert Testimony

Expert testimony includes quotations from scholars and summaries of previous research or scholarship. Expert testimony can reinforce an argument; however, a quotation by an expert with similar claims is rarely sufficient as evidence on its own. Authors must explain how those experts support their claims and then reinforce their own claim with evidence from other sources.

Before quoting an expert, an author must determine whether he or she counts as an authority. Just because someone has published an academic paper or book does not mean that readers will believe his or her theories are valid. In the sciences and social sciences, readers should expect expert testimony to be the most current research. Quoting a paper written even ten years ago may not be convincing expert testimony.

In the sciences, readers rarely expect direct quotations of secondary sources as evidence. Instead, science writers use summaries of previous research and the findings, or data, to support their own claims.

Interviews and Surveys

Results from a Dallas Morning News article survey relating to students and digital social networking.

Interviews and surveys are often used as evidence in the social sciences. For example, a psychology paper might interview teachers and parents about their children’s gender identities and then observe their children’s behavior when playing. Quotations and detailed descriptions of an author’s observations count as evidence in examples like these.

Surveys are often mistaken for “facts” or used as “data.” While they look like statistics or “hard numbers,” surveys are created through interviews. Therefore, when seeing a survey as evidence, whether it is one an author created or one found through research, it is important for readers to understand the method of the survey. Who were the participants? How were they selected? How were the questions phrased? Surveys are valid evidence in many disciplines, but they require explanation before readers trust the numbers.

Personal Anecdotes

In some texts, stories about an individual’s personal experience may be appropriate. Personal anecdotes may be appropriate in some sociology or psychology papers, but only when accompanied by additional evidence. In some humanities writings, personal anecdotes are acceptable as a stylistic choice in the conclusion or introduction, but not as evidence in the body paragraphs.

Readers will not be persuaded by personal anecdotes if authors rely on them to support all claims or use them to support a controversial claim. Readers will wonder whether someone’s personal experience represents a common occurrence, or one that just happened to that one person.