Types of Evidence Commonly Used in Speeches
Types of Evidence Commonly Used in Speeches
Examples
When you consult a dictionary, you learn that an example is a sample of something. Ideally, the example will be representative of the class. That is, the example will have features typical of thing it represents.
Conversely, we are aware that an example may be atypical. For some reason or circumstance, a specific example may be an anomaly and would not normally be expected to represent that class of items.
Numbers and Statistics, and Surveys
Many people remember the phrase popularized by Mark Twain that there are “lies, damn lies, and statistics.” Many people hold the belief that you can make statistics say whatever you wish. For example, if a speaker says that “nine out of ten people surveyed said...” then the doubter would ask “how many people were surveyed” and “how were they chosen?”
Surveys can be tricky as items of proof. Consequently, when citing a survey, the rhetor should include several key pieces of information: When was the survey conducted? Who conducted it? How were people selected? What specific question was asked? And what is the margin of error? Take careful note of that information as you collect information.
Testimonials
This type of proof is used to provide the audience insight into an event/topic from someone who has direct knowledge of that event/topic. The persuasive impact of someone who has direct knowledge of a topic is often viewed as highly credible. Such testimony lends personal knowledge or insight into a topic, thus making it more real to the audience.
Analogies
This type of proof is quite useful to a speaker. In general, an analogy relates something familiar to an audience with something unfamiliar. Thus, the audience is able to grasp something about the topic that was previously vague or incomprehensible.
I remember attending a seminar one time sponsored by a railroad company. One of the engineers who spoke that day tried to explain why it was so important for motorists to understand the danger of trying to out run a train at a street crossing. He argued that the impact of a train traveling at 30 miles an hour hitting a car broadside was the equivalent of a car running over an empty Coke can. That illustration stuck with me for twenty years. That’s powerful! Explanations. Every day we are asked to supply reasons for what we do or think. That’s an explanation! When we list these reasons, we are clarifying our decision making process. One of the reasons for providing an explanation in a speech is to establish common ground with the audience and to get them to consider the steps used in making a particular decision. Even if the audience disagrees with the decision or the reasons for making them, the process of decision making is clarified.
Definitions
Most of us know that a definition provides a precise description of the thing we are discussing. Often, we assume that everyone knows what we are talking about when, in fact, each of us may have a different mental perception of a thing. Using a definition in a speech insures that everyone is working from the same basic set of assumptions.
Arguments, Evidence and Proof
When we speak, we construct arguments in an attempt to establish common ground with the listeners. Evidence is used to bolster the claims we make. Evidence, as we have discussed above, can take a number of forms from definitions to testimonies. We could easily mistake arguments and evidence as proof. Yet proof is more illusive. It is the result of evidence and arguments the listener accepts as valid that leads to a conclusion the listener accepts as true. When we approach an audience, we ask them to reason with us for a while. We ask that they consider the claims we make and, hopefully, agree with the conclusions we draw. Our job as speakers is to make the case as convincingly as possible in an attempt to prove our case. Yet we must be aware that audience members are the final judges of our efforts.
Resources at Your Disposal
Everyone has their favorite resources. You find these by trial and error. One of my favorite sources for academic studies is a subscription service called Questia.com. No one is paying me to say that, I just like it.
Reference librarians and professors are wonderful resources. They often know how to find things more quickly, but I would advise you that the pace of information exchange is so rapid that resources come and go and a fast clip. Even the ones listed here may be outdated by the time you use them. I suggest that you develop your own web page of handy references. You can see mine at http://faculty.smu.edu/rkirk
