Department of Communication

Evidence

Since evidence must ultimately be persuasive to an audience, arguers must adjust their usage of evidence for maximum appeal. The following tips are for framing evidence for maximum efficiency. Since argumentation is a social and communicative process, rhetorical technique enhances the persuasiveness of evidence.

Criteria for Evaluating Evidence

The following criteria are often employed in evaluating evidence that supports arguments:

Tips for Using Evidence

Be consistent with audience beliefs. Evidence is more likely to be accepted if it is condidered consistent with an audiences’ beliefs. Of course, arguers often find themselves in situations where the audience beliefs are at odds with the evidence for their case—thus, they should attempt to undermine audience resistance to their evidence. Advancing a claim about the value of gun control for automatic weapons in a debate for the NRA will require work to have the audience accept evidence presented.

Maintain source appropriateness. Some sources are more compelling to particular audiences than others. In a debate about gender equality, arguers might be wise to avoid quoting from Playboy; in a debate about the existence of aliens, arguers might be wise to avoid quoting from the X-Files fan web site.

Acknowledge counterevidence. Smart arguers will acknowledge the presence of counterevidence and make comparisons with their own evidence or indictments of their co-arguer’s evidence. For example, an arguer might say “While there is some evidence that indicates otherwise, the evidence I have just presented is superior because…”

Rate evidence. Since all evidence was not created equal, make value judgments as the evidence is presented. For example, an arguer might say “The best study indicates that…”

Utilize sphere specific resources. Different spheres—public, private, and technical types of argument—require different norms for argumentation. Using highly technical terms for a lay audience would be ineffective; whereas using a technical terms for a group of physicists would be preferred.

Include details. Informing the audience of the details of a study, or methodology for research, enhances the suasory power of evidence. For example, an arguer might say “Utilizing both qualitative analyses of texts and quantitative analyses of survey data…”

Rely on experience. Argument’s search for common ground encourages utilizing agreed upon starting points for introducing evidence. For example, an arguer might say “From your experience as a decision-maker, you know that this type of evidence is most persuasive…”

Document evidence. Identifying the source for supporting material can enhance credibility, and allow the audience to follow up with their own additional research if desired. Well-documented sources enable audiences to conclude that there is substantial support for the speaker’s argument.