The Language of Argument

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c hAp tEr 9 ■ I n f e r e n c e t o t h e B e s t E x p l a n a t i o n a n d f r o m A n a l o g y

that you have been burglarized. Of course, other things could have produced

the mess. Perhaps the police mistakenly busted into your house looking for

drugs and took your valuables as evidence. Perhaps your friends are playing

a strange joke on you. Perhaps a meteorite struck the door and then vaporized

your valuables. In fact, all of these things could have happened (even the last),

and further investigation could show that one of them did. Why, then, do we

so quickly accept the burglary hypothesis without even considering these

competing possibilities? The reason is that the hypothesis that your home

was robbed is not highly improbable; and this hypothesis, together with other

things we believe, provides the best—the strongest and the most natural—

explanation of the phenomenon. The possibility that a meteorite struck your

door is so wildly remote that it is not worth taking seriously. The possibil-

ity that your house was raided by mistake or that your friends are playing a

strange practical joke on you is not wildly remote, but neither fits the overall

facts very well. If it was a police raid, then you would expect to find a police

officer there or at least a note. If it is a joke, then it is hard to see the point of it.

By contrast, burglaries are not very unusual, and that hypothesis fits the facts

extremely well. Logically, the situation looks like this:

(1) Observation: Your lock is broken, and your valuables are missing.

(2) Explanation: The hypothesis that your house has been

burglarized, combined with previously accepted facts and

principles, provides a suitably strong explanation of observation 1.

(3) Comparison: No other hypothesis provides an explanation nearly

as good as that in 2.

∴(4) Conclusion: Your house was burglarized.

The explanatory power of the conclusion gives us reason to believe it

because doing so increases our ability to understand our observations and to

make reliable predictions. Explanation is important because it makes sense

out of things—makes them more intelligible—and we want to understand

the world around us. Prediction is important because it tests our theories

with new data and sometimes allows us to anticipate or even control future

events. Inference to the best explanation enables us to achieve such goals.

Here it might help to compare inferences to the best explanation with

other forms of argument. Prior to any belief about burglars, you were

already justified in believing that your lock was broken and your valuables

were missing. You could see that much. What you could not see was why

your lock was broken. That question is what the explanation answers.

Explanations help us understand why things happen, when we are already

justified in believing those things did happen. (Recall Chapter 1.)

Explanations often take the form of arguments. In our example, we could

argue:

(1) Your house was burglarized.

(2) When houses are burglarized, valuables are missing.

∴(3) Your valuables are missing.

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