5.2: Evidence: Proving Your Point

As you see, individual pieces of evidence are used to build your argument. In this section, we identify some common types of evidence as well as approaches to help explain your ideas to your audience.

• A definition is a precise meaning or significance of a word or phrase. In an argument, it can be helpful to establish a common frame of reference for important or ambiguous words, so don’t underestimate the importance of definitions.
• An example is a specific instance chosen to represent a larger fact in order to clarify an abstract idea or support a claim. Good examples must be appropriate, brief and attention arresting. Quite often they are presented in groups of two or three for impact.
• Testimony uses the comments of recognized authorities to support your claim. These comments can be direct quotations or paraphrases, but direct quotations tend to carry more weight with listeners or readers. When using testimony as support, make sure the individuals being quoted are both generally credible-no unknown relatives or convicted felons, please-and knowledgeable in the field under discussion.
• Statistics provide a summary of data that allows your audience to better interpret quantitative information. Statistics can be very persuasive and provide excellent support if handled competently. Keep them simple and easy to read and understand. Also, remember to round off your statistics whenever possible and document the exact source of your statistics.

The persuasive power of statistics means that you need to be particularly careful to use them properly. Many people will put blind trust in numbers and fall prey to people or papers that spout numbers or statistical proof. (Ironically, people who work with numbers for a living are the most cautious about trusting someone else’s statistics!).

Always, always examine the basic assumption(s) on which the analysis rests. Some of the most compelling statistical arguments turn out to be intricate sand castles built on a foundation of shaky assumptions. The math may be technically correct, but the assumptions can’t stand up to scrutiny.

In their book Writing Arguments, John Ramage, John Bean, and June Johnson define a fact as a noncontroversial piece of data that can be confirmed by observation or by talking to communally accepted authorities. The authors distinguish a fact from an inference, which is an interpretation or explanation of the facts that may be reasonably doubted. They recommend that writers distinguish facts from inferences and handle inferences as testimony. Definitions, testimony, statistics and facts provide data that you can use to construct an argument. This next category explanation-can also be helpful in supporting your ideas.

• Explanation makes a point plain or understandable or gives the cause of some effect. It can be used to clarify your position or provide additional evidence to help make your case. The following three techniques can be used as part of an explanation:
• Analysis: The separation of a whole into smaller pieces for further study; clarifying a complex issue by examining one piece at a time.
• Comparison and Contrast: Comparison and Contrast are birds of similar feather. Use comparison to dramatize similarities between two objects or situations and contrast to emphasize differences.
• Description: To tell about in detail, to paint a picture with words-typically more personal and subjective than definition.