14.6: Criteria for Creating Good Explanations

We create explanations to show our listeners or readers how something works or how things got to be the way they are. If you're creating an explanation for why China has so many more people than Siberia, you may want to talk about history and the social, political, and geographical forces shaping those two areas of the world. In doing so, you take it for granted that your audience accepts the fact that China really does have more people than Siberia. If you have to get your audience to first accept this fact, you need to argue for it, not explain it.

To create a good explanation of something is not easy. In this section we will examine some of the faults in explanation construction and then introduce criteria for constructing good explanations. Explanations have many features in common with arguments, so many of these criteria apply to constructing good arguments as well.

The explanation should fit the facts to be explained and should not conflict with other facts. When you are explaining an event, you must show why the event should have occurred, and your explanation should not be inconsistent with any facts. For example, suppose you want to explain why your friend recovered from the flu after only four days of being ill. Here is an explanation of this event: Your friend drank five glasses of orange juice every day he was sick, and drinking orange juice in such heavy doses will knock out anybody's flu virus within four to six days. This explanation does imply that your friend's recovery is to be expected. That's a plus for the explanation. Unfortunately, a doctor can tell you that many, many flu victims who have been tested with orange juice this way have not recovered for several weeks. So your explanation is in conflict with the facts about these other people. Consequently, the explanation violates our rule and should be rejected.

An explanation should do more than merely describe the situation to be explained. For example, suppose we ask a psychic, "How do you successfully locate oil and gold with your mental powers?" and she answers, "Geologists conduct an initial survey of the area for me. Afterward I fly over it, extend my hand, and sense the location of the underground deposit. Or I run my finger over a map and point out where to drill." This answer describes the sequence of events leading up to the event to be explained, but it is intellectually unsatisfying, since we wanted to find out more details about the cause of the psychic's supposed success. We hoped for a causal explanation that would show what makes the psychic's actions work for her when they won't work for us.

Good explanations are not circular. A good explanation doesn't just rephrase what it is trying to explain. A biologist makes this mistake if she tries to explain why humans have two feet by saying it is because they are bipeds. It is true that humans are bipeds, but the definition of biped is "two-footed animal," so the biologist's “explanation” merely names the phenomenon; it does not explain it. It does not give us what we want—either the causal mechanism that makes humans have two legs instead of some other number, or some evolutionary story of the genesis of two legs in humans. What would a noncircular explanation look like? Well, the causal explanation might say that our genes control growth and force humans to have two legs as they develop. A second kind of explanation could point out how, through evolution, a gradual change occurred in hip structure as our ancestors adapted to situations that favored walking on two legs. Whether either of these two explanations is correct is another matter; however, neither of them is circular.

Supernatural explanations should be avoided unless it is clear that more ordinary, natural explanations won't work. For example, suppose Inge says, "I got skin cancer because my number came up; evidently it was my time. She is explaining her cancer as being the consequence of some supernatural force that intervenes into the natural causal order of things and makes events happen; this is the supernatural force we call "fate." It's not impossible that she is correct, but her explanation is very weak. Here is a better explanation: Inge works in a manufacturing plant where she comes in daily contact with benzene fumes, and benzene is a well-known cause of skin cancer, so the benzene caused Inge's skin cancer. Until we rule out benzene, let's not pay much attention to fate.

Good explanations are relevant. A Toyota is a Japanese car. If I explain why Julie has never owned a Toyota by saying that she hates German cars, I can be accused of violating the need for relevancy. Her hating German cars might explain why she doesn't own a BMW, but it's not clearly relevant to why she doesn't own a Toyota. If there is some connection, it should have been stated as part of the explanation.

Explanations should be consistent with well-established results except in extraordinary cases. Suppose I explain why I have a headache almost every day at noontime by pointing out that at noon I'm the closest I am to the sun all day; because the sun's gravitational pull on me is strongest at noon, its pull must be the cause of my headaches. This would be an odd explanation. It is a well-established scientific fact that the sun does exert a gravitational pull on us and that this pull is strongest at noon. However, it is also well established that our bodies are insensitive to these small gravitational changes. So, I should look elsewhere for the cause. The inconsistency of my explanation with well justified scientific theory detracts from the quality of my explanation. My explanation might still be correct, but for it to be convincing to the experts a revolution would have to occur in the field of biology. Extraordinary explanations are those that require big changes in the beliefs of the experts, and extraordinary explanations require extraordinarily good evidence. An ordinary explanation of the headaches, such as their being caused by my eating a half-pound of beets only on the days I get the headaches, would be a more promising explanation if it’s true that I do eat beets that often.

We do not need a great deal of evidence to be convinced that

the kitchen cup made a sound during the night because a rat pulled it over,

but we should demand an extraordinarily large amount of high-quality evidence to be convinced that

the kitchen cup made a sound during the night because a ghost kicked it.

Explanations should be tailored to the audience whenever possible. Suppose we try to explain the red marks on Emilio's nose as being due to overexposure to sunlight. If our audience already knows that sunlight can cause skin cancer and that skin cancer can cause red marks, we may not need to add any more to the explanation beyond perhaps reminding the audience of these facts. However, if the audience doesn't know these facts, we are obliged to support the facts. Also, our explanation should be pitched at the proper level of difficulty for our audience; we cannot use technical terminology on an audience that won't understand the technical terms. Explanations are easier to understand if they explain something unfamiliar in terms of something familiar, even if being easy to understand is not a sign of being correct. Most of us are unfamiliar with the principles of electricity, such as the relationship between current and voltage, but we are familiar with how water flows through a pipe. So, a good explanation of electricity for us might be based on an analogy between electrical current and water flow:

The amount of water flowing through a pipe per second is analogous to the amount of electrical charge flowing through a wire per second, and this amount is called the electrical "current." If you want to increase water flow, you’ve got to increase the water pressure. Similarly, if you want to increase the electrical current in a wire, you have to turn up the voltage.

OK, that helps explain the behavior of electricity to an audience untutored in physics, but it’s not a correct explanation that would convince the scientific community. Correct explanations might be very difficult to understand, as you’d find out if you tried to read the paper of 1864 written by James Clerk Maxwell that really did explain electricity to the scientists.

The more precise the explanation, the better. Excessive vagueness weakens an explanation. The more precise a claim, the easier it is to test and thus to refute. If someone claims that eating five medium-sized dill pickles will bring on a headache within twelve minutes, you can test it on someone, perhaps yourself. However, if the person is vaguer and instead claims only that eating pickles will produce headaches, you have a tougher time. What kind of pickles? What size? How many? Will eating them produce headaches in five minutes, five days, next year? The vague claim is too hard to test. The more precise claim is more easily refuted, if it is false, but it tells us so much more if it can’t be refuted. This is why precise claims are said to be more "scientific" than vaguer ones.

Testable explanations are better than untestable ones. Saying "She wasted all her month's food money on lottery tickets because she was in the wrong place at the wrong time" would be an example of an untestable explanation. How do you test it?

Exercise \(\PageIndex{1}\)

All the following statements are trying to explain why tigers eat meat but not plants. Which explanation is the best, and why? Remember, an explanation is not trying to be an argument.

a. Tigers are carnivores.
b. Professor DeMarco says so, and he is an expert on tigers.
c. Tigers are naturally meat eaters, because many years ago the most powerful witches on earth placed a spell on the tigers and forced them to be that way.
d. Tiger cells contain a gene that prevents their stomachs from digesting plant cells.
e. My science textbook says tigers eat meat but not plants.

Answer

Answer (d) is best. Although (d) is probably not a correct explanation of why tigers are carnivores, at least it is testable, consistent with well-justified biological theory, not circular, and does not appeal to the supernatural. Answer (a) is circular because carnivore just means "eater of flesh, not plants." Answer (b), like (e), is an argument, not an explanation; it provides a good argument for believing that tigers are meat eaters and not plant eaters, but it gives no explanation of why tigers are this way. Answer (c) is not acceptable because it violates the canon to be cautious about offering supernatural explanations until it is clear that more ordinary, natural explanations won't work.