Chapter 6 Chapter Summaries

CHAPTER 6 SUMMARY

• An expert is someone who is more knowledgeable in a particular subject area or field than most others are. Experts provide us with reasons for believing a claim because, in their specialty areas, they are more likely to be right than we are. They are more likely to be right because (1) they have mastered particular skills or bodies of knowledge, and (2) they practice those skills or use that knowledge as their main occupation in life.

Experts and Nonexperts

• We must rely on experts, but critical thinkers are careful about expert opinion, guiding their use of experts by some commonsense principles. The most basic of these commonsense principles is: If a claim conflicts with other claims we have good reason to accept, we have good grounds for doubting it.
• Sometimes a claim will conflict with your background information. Background information is the large collection of very well supported beliefs that we rely on to inform our actions and choices. The relevant principle is: If a claim conflicts with our background information, we have good reason to doubt the claim. It’s not reasonable to accept a claim if there is good reason to doubt it. In the case of claims that we can neither accept nor reject outright: We should proportion our belief to the evidence.
• When it comes to expert opinion specifically, two principles hold. The first is: If a claim conflicts with expert opinion, we have good reason to doubt it. The second is: When the experts disagree about a claim, we have good reason to doubt it. When we rely on bogus expert opinion, we commit the fallacy known as the appeal to authority. This usually occurs in one of two ways. First, we may find ourselves disregarding this important rule of thumb: Just because someone is an expert in one field, he or she is not necessarily an expert in another. Second, we may fall into a fallacious appeal to authority by regarding a nonexpert as an expert.

Judging experts

• In most professional fields, two indicators are considered minimal prerequisites for being considered an expert: (1) education and training from reputable institutions or programs in the relevant field and (2) experience in the field. However, people can have the requisite education and experience and still not know what they’re talking about in the field in question. Therefore, two additional indicators are more revealing of expertise: (1) reputation among peers and (2) professional accomplishments.
• We sometimes have reason to doubt the opinion of the experts, in which case we are not justified in believing a claim based on that opinion. Chief among possible reasons for doubt (aside from conflicting expert opinion) is bias. When experts are biased, they are motivated by something other than the search for the truth such as financial gain, professional ambition, emotional needs, political outlook, or some other judgment-distorting factor. Other reasons for doubting an expert’s claims include: blatant violations of critical thinking principles, simple factual or formal errors, a lack of adequate support for his or her assertions, and unfair treatment of opposing views.
• Qualified experts who are honest and unbiased can sometimes get things wrong. Error is in the nature of expertise, especially when it comes to predictions. Nonetheless it remains true that, in general, genuine experts are more likely to be right about things in their fields than we are.

Experts and Personal Experience

• Many claims we accept are based on personal experience, ours or someone else’s. We can trust our personal experience—to a point. The relevant guiding principle is: It’s reasonable to accept the evidence provided by personal experience only if there’s no reason to doubt it. Some common factors that can raise such doubts are impairment (stress, injury, distraction, emotional upset, and the like) and the way expectations can affect the reliability of our perceptions.

Innumeracy and Probability

• Because humans generally have difficulty figuring probabilities, critical thinkers must be careful when making claims about the chances of something happening. One common error is misjudging the probability of coincidences. Another error is to think that previous events can affect the probabilities in the random event at hand, a mistake is known as the gambler’s fallacy.