5.5: Evaluating Testimony in General

We constantly rely on the claims of people who are not experts in any well established field. We ask a stranger for directions to the Student Union. We ask friends and acquaintances which restaurants are worth going to and which are best avoided. If we are contemplating dating someone, we might ask their exes how things worked out.

We also appeal to people in general; “They say that…”. When we appeal to the fact that people in general (or people in some group we care about) think some claim is true, we are employing an appeal to authority called an appeal to popularity. Such appeals are common, and they can be very effective. In extreme cases, a bandwagon effect occurs, in which large numbers of people embrace a view (or support a cause, like a political candidate) because other people have done so. Some people jumped on the bandwagon, and since others don’t want to be left behind, they jump on too. We should always be careful not to rely on popularity alone to establish the truth or falsity of a claim. It is important to remember popularity itself doesn’t justify a view. If someone makes an appeal to popularity, we should ask ourselves why it is popular and if those reasons support the position independently.

When we appeal to the fact that people have traditionally thought that some claim was true, we are employing an appeal to authority called an appeal to tradition. Such appeals may be legitimate, but they often are not. It depends on whether the group, either people now or people in the past, are reliable judges regarding the issue in question.

Normally we believe much of what we hear, and unless there is a good reason not to, that is entirely sensible. But anyone can be mistaken, and sometimes people lie. Furthermore, there are various pitfalls, including halo effects. Just as we are more likely to take the word of people who seem to be experts, we are more likely to change our views due to claims by someone to whom we feel similar. We will also see that one of the strongest halos is created by physical attractiveness, and it has been found that people are more persuaded by people they find physically attractive.

Most of the considerations that are relevant to evaluating the reliability of experts also apply when evaluating the reliability of your roommate, your Aunt Sally, or even a stranger on the street. Indeed, we could regard such people as experts about some limited subject matter, like the restaurants in Norman, or romantic interludes with Wilbur.

The Seven Questions Revisited

Now, let’s quickly run back through the seven questions to ask about alleged experts and see how they apply to testimony in general, regardless of the source.

1. Do we care enough about this issue to try to evaluate the likelihood that a given source about it is accurate?

The general point here is the same, whether the potential source is a world-class expert or just someone we meet on the street. But the costs of getting information from someone you know or encounter by chance may be lower than the costs of getting information from an expert, so it may be reasonable to collect more information from those around you.

2. Is the issue one in which anyone can really be relied on to know the facts?

The point here is the same, regardless of the source. If there are no experts in the field, then there is little likelihood that your friends and acquaintances will be particularly good sources of information about it.

3. Is the source generally right about this sort of issue?

Perhaps Anne has always given good advice on fixing computers, while Sam has often been wrong. Sally has always provided good advice about who to date, while Wilbur’s advice is hopeless. In such cases, we should consider the sources with the best track records to be the most trustworthy.

4. Is the issue one where people would mostly agree?

If there is little agreement among others about something, you are on your own.

5. Is the source’s claim very unusual or surprising?

The point here is the same regardless of the source. If a claim is sufficiently unlikely, it is more probable that the source is wrong than that the claim is true.

6. Is there any reason to think that the source might be biased or mistaken in this case?

Breona is a good judge of people and full of insights about their personalities, but she has a blind spot about Eduardo. Dalton usually gives good advice, but he’s really been stressed out lately. John saw the car that sideswiped me, but it was dark, and he could have made a mistake about its license number. Indeed, as we will see later in this module, even honest eyewitnesses are much less reliable than people commonly suppose.

7. Has the source been quoted accurately?

Xavier tells us that Breona said that Carmen and Jasmine are back together again. Is there any reason to think Xavier might be getting it wrong? As we add more people to the chain of testimony, we increase the possibility for error and as a result, our concern about the veracity of the claim.