Evidence in a Persuasive Speech

Learning Objectives

Identify effective evidence for a persuasive speech.

Information signPart of being perceived by your audience as a credible speaker involves using evidence well suited to the topic of the speech and the audience you are speaking to. Imagine if a speaker made an argument that in 30 days Earth would be invaded by Martians. You’d want to see some credible evidence supporting that claim, right?

We likely won’t be making that exact argument in this class, but regardless of whether we are arguing that Martians are going to invade Earth or that Doc Martens are the best shoes, we want to support our claims with helpful, credible, and convincing evidence.

Evidence is necessary to use in a speech because in a speech class we typically are not recognized as an expert on the subjects we speak about. Demonstrating we have taken the time to research our topic enhances our credibility as a speaker and adds to the persuasive appeal of our argument. Each main point you make in a persuasive speech should be supported by at least one type of evidence.

Evidence is also crucial when you are speaking to an audience that doesn’t agree with your perspective. Careful use of evidence can help you answer the questions that audience members who don’t agree with you may have about the argument you are making.

As a reminder, there are two broad categories of research we can draw from for a speech:

  • Nonacademic sources, which include books, general interest or trade periodicals, newspapers, blogs, social media sites, and websites like Wikipedia. Nonacademic sources can be a good starting point for research.
  • Academic sources, which include books, scholarly articles, journal databases, and web resources. Academic sources are usually peer reviewed by experts and they generally are more specific in focus and tailored to an audience of highly knowledgeable readers than nonacademic sources.

There are several sources of evidence that can help establish your credibility as a persuader:

  • Testimony from experienced and expert individuals will lend credibility to your speech. If there is an expert on your speech topic on your campus or in your community, you could interview them and use their testimony as supporting evidence in your speech.
  • The internet can be a terrific source of credible nonacademic supporting evidence. It can also be a source of terrible supporting evidence. So be careful to not only evaluate the content you get off the internet—data from a study, statistics, quotes from an authority, etc.—but the source of that content as well.  Are you citing information from someone’s personal blog, for example? Or are you citing evidence from a website where information is vetted by editors or experts before it is published? The information published on one isn’t necessarily less credible than the other, but we should try and learn something about the qualifications of the person writing on their blog in order to evaluate their knowledge of the subject they are writing about.
  • Library resources, such as books, periodicals, academic journals and databases, and reference material are also excellent sources. We may not think of libraries first, given how easy it is to search for information on the internet, but libraries are sources for high quality, credible information. In addition, librarians can be a great resource for you in helping you narrow or widen the scope of your research and find sources that would be suitable for your topic.

As you are pulling together your research, it’s helpful to ask yourself a few questions such as:

  • Am I drawing from a wide enough variety of sources that allows me to see a full range of perspectives on my topic?
  • Am I choosing sources that are reputable and credible?
  • Do the sources I am choosing have an agenda or bias I need to be aware of? And if I use a source with an agenda or bias, how should I present that information in my speech? Generally audiences will find evidence from a neutral source more persuasive than from a source with a bias or agenda.
  • Am I verifying that the information I find through one source is corroborated by other sources? Generally it’s good practice to verify a claim made by one source by checking it against at least one other reputable source.

Try It