One fairly common way to argue is the argument from authority. While people rarely follow the “strict” form of the argument, the basic idea is to infer that a claim is true based on the allegation that the person making the claim is an expert. For example, someone might claim that second hand smoke does not cause cancer because Michael Crichton claimed that it does not. As another example, someone might claim that astral projection/travel is real because Michael Crichton claims it does occur. Given that people often disagree, it is also quite common to find that alleged experts disagree with each other. For example, there are medical experts who claim that second hand smoke does cause cancer.
If you are an expert in the field in question, you can endeavor to pick between the other experts by using your own expertise. For example, a medical doctor who is trying to decide whether to believe that second hand smoke causes cancer can examine the literature and perhaps even conduct her own studies. Being an expert, a person is presumably qualified to make an informed pick. The obvious problem is, of course, that experts themselves pick different experts to accept as being correct.
The problem is even greater when it comes to non-experts who are trying to pick between experts. Being non-experts, they lack the expertise to make authoritative picks between the actual experts based on their own knowledge of the fields. This raises the rather important concern of how to pick between experts when you are not an expert.
Not surprisingly, people tend to pick based on fallacious reasoning. One common approach is to pick an expert based on the fact that she agrees with what you already believe. That is, to infer that the expert is right because you believe what she says. This is rather obviously not good reasoning: to infer that something is true simply because I believe it gets things backwards. It should be first established that a claim is probably true, then it should be believed (with appropriate reservations).
Another common approach is to believe an expert because he makes a claim that you really want to be true. For example, a smoker might elect to believe an expert who claims second hand smoke does not cause cancer because he does not want to believe that he might be increasing the risk that his children will get cancer by his smoking around them. This sort of “reasoning” is the classic fallacy of wishful thinking. Obviously enough, wishing that something is true (or false) does not prove that the claim is true (or false).
People also pick their expert based on qualities they perceive as positive but that are, in fact, irrelevant to the person’s actually credibility. Factors such as height, gender, appearance, age, personality, religion, political party, wealth, friendliness, backstory, courage, and so on can influence people emotionally, but are not actually relevant to assessing a person’s expertise. For example, a person might be very likeable, but not know a thing about what they are talking about.
Fortunately, there are some straightforward standards for picking and believing an expert. They are as follows.
1. The person has sufficient expertise in the subject matter in question.
Claims made by a person who lacks the needed degree of expertise to make a reliable claim will, obviously, not be well supported. In contrast, claims made by a person with the needed degree of expertise will be supported by the person’s reliability in the area. One rather obvious challenge here is being able to judge that a person has sufficient expertise. In general, the question is whether or not a person has the relevant qualities and these are assessed in terms of such factors as education, experience, reputation, accomplishments and positions.
2. The claim being made by the person is within her area(s) of expertise.
If a person makes a claim about some subject outside of his area(s) of expertise, then the person is not an expert in that context. Hence, the claim in question is not backed by the required degree of expertise and is not reliable. People often mistake expertise in one area (acting, for example) for expertise in another area (politics, for example).
3. The claims made by the expert are consistent with the views of the majority of qualified experts in the field.
This is perhaps the most important factor. As a general rule, a claim that is held as correct by the majority of qualified experts in the field is the most plausible claim. The basic idea is that the majority of experts are more likely to be right than those who disagree with the majority.
It is important to keep in mind that no field has complete agreement, so some degree of dispute is acceptable. How much is acceptable is, of course, a matter of serious debate.
It is also important to be aware that the majority could turn out to be wrong. That said, the reason it is still reasonable for non-experts to go with the majority opinion is that non-experts are, by definition, not experts. After all, if I am not an expert in a field, I would be hard pressed to justify picking the expert I happen to like or agree with against the view of the majority of experts.
4. The person in question is not significantly biased.
This is also a rather important standard. Experts, being people, are vulnerable to biases and prejudices. If there is evidence that a person is biased in some manner that would affect the reliability of her claims, then the person’s credibility as an authority is reduced. This is because there would be reason to believe that the expert might not be making a claim because he has carefully considered it using his expertise. Rather, there would be reason to believe that the claim is being made because of the expert’s bias or prejudice. A biased expert can still be making claims that are true—however, the person’s bias lowers her credibility.
It is important to remember that no person is completely objective. At the very least, a person will be favorable towards her own views (otherwise she would probably not hold them). Because of this, some degree of bias must be accepted, provided that the bias is not significant. What counts as a significant degree of bias is open to dispute and can vary a great deal from case to case. For example, many people would probably suspect that researchers who receive funding from pharmaceutical companies might be biased while others might claim that the money would not sway them if the drugs proved to be ineffective or harmful.
Disagreement over bias can itself be a very significant dispute. For example, those who doubt that climate change is real often assert that the experts in question are biased in some manner that causes them to say untrue things about the climate. Questioning an expert based on potential bias is a legitimate approach—provided that there is adequate evidence of bias that would be strong enough to unduly influence the expert. One way to look for bias is to consider whether the expert is interested or disinterested. Or, more metaphorically, to consider whether they have “skin in the game” and stand to gain (or suffer a loss) from a claim being accepted as true. Merely disagreeing with an expert is, obviously, not proof that an expert is biased. Vague accusations that the expert has “liberal” or “conservative” views also do not count as adequate evidence. What is needed is actual evidence of bias. Anything else is most likely a mere ad homimen attack.
These standards are clearly not infallible. However, they do provide a good general guide to logically picking an expert. Certainly more logical than just picking the one who says things one likes.