What makes an argument persuasive? But, of course, evidence! To rely on metaphors: evidence is like spices to a casserole, giving flavor and uniqueness to a dish; evidence plays the role of different lamps used in theater to spotlights certain characters or monologue/dialog in a scene.
Evidence represents verifiable information a writer uses as support for an argument. Evidence is parts of the ‘grounds’ or ‘backing’ of an argument. Evidence can be facts, observations, examples, cases, testimony, experimental findings, survey data, statistics, etc.
A targeted audience of educated, reasonable, and careful readers who approach an issue with healthy skepticism, open-minded but cautious, looks for STAR criteria:
- Sufficiency: Is there enough evidence? How much evidence you need will depend on the claim you make and the skepticism of the audience regarding your argument. Example: Strong claim: “Working full time seriously harms a student’s grade point average” – Much data needed, probably a combination of examples and statistical studies. Qualified claim: “Working full time often harms a student’s grade point average.” – A few representative examples may be enough
- Relevance: Is the evidence relevant to the claim? When choosing your evidence to support your arguments, you always need to control the space given to supporting versus contrary evidence. You need to make compromises: emphasizing a detailed story versus presenting lots of facts and statistics. But, always you need to provide contextual and interpretative comments when presenting your data. How to deal with contrary evidence? In most cases you will have to address the counter-argument, but you do so by putting contrary evidence in subordinate position.
- Typicality: Is the chosen evidence representative and typical? This relates to the representatives of the data you present as supporting facts. Some data are more representative (like representative surveys), other might be more narrow (personal narratives). For example: if you rely on a narrative story to support an argument, you need to think how many stories like that exist out there?
- Accuracy: Is the evidence accurate and up-to-dated?Accuracy of information helps you build credibility as a writer. If your facts don’t check out, well, your claims will be questioned as will your professionalism as a writer. So, you need to be very knowledgeable about your issue. But, at the same time you need to be fair: provide fairness and courtesy to alternative points of view.
A Checklist for brainstorming sources of evidence
- What personal evidences you had with this issue? What details from your life or lives of your people you know might serve as examples?
- What observational studies would be relevant to this issue?
- What persons could you interview to provide insights or expert knowledge on the issue?
- What questions about your issue could be addressed in a survey or questionnaire?
- What library resources might contain evidence for your issue?
- What evidence might you seek from databases indexing sources in magazines, newspapers, and scholarly research (LexisNexis database)?
- How might an internet search engine help you research the topic?
- What evidence might you find on this issue from reliable statistical resources such as U.S. census Bureau data, etc?
No matter what type of evidence or data you decide to use in support of your arguments, they all have their strengths and weaknesses. Therefore, the most persuasive arguments are built on a plethora of facts originating form a variety of sources.
Pros: Help readers identify with writer and show writer’s personal connection with the issue.Vivid stories capture imagination.
Cons: Skeptics may argue that personal experience is not sufficient and might not be typical or adequately verifiable
Observations and field research
Pros:Gives the feeling of scientific credibility. Provides more than one example. Enhances ethos of the writer as personally invested and reasonable
Cons: Skeptics may point the flows on how the observations were conducted, showing how data are insufficient, inaccurate, or non-typical.
Interviews and Surveys
Pros: Enhance the sufficiency and the typicality of evidence by providing data beyond the experience of one person. Quantitative data increase the scientific level of the argument. Interview can provide engaging personal stories enhancing pathos.
Cons: Skeptics can raise doubts about research methodology, the questionnaire, or the typicality of the subjects interviewed.
Pros: It is generally less persuasive that direct data. It can be persuasive if the source has impressive credentials.
Cons: Skeptics might undermine testimonial evidence by questioning the credentials of a source.
Pros: Can give powerful snapshots of aggregate data from wide database. Can use nice graphics for illustration
Cons: Skeptics might question statistical methods, research design, and interpretation of the data.