1 9 7I n f e r e n c e s t o t h e B e s t E x p l a n a t i o nThis explanatory argument starts with the hypothesis that was the conclusion
of the inference to the best explanation, and it ends with the observation that
was the first premise in that inference to the best explanation. The differ-
ence is that this new argument explains why its conclusion is true—why the
valuables are missing—whereas the inference to the best explanation justified
belief in its conclusion that your house was burglarized.
More generally, in an explanatory use of argument, we try to make
sense of something by deriving it (sometimes deductively) from premises
that are themselves well established. With an inference to the best explana-
tion, we reason in the opposite direction: Instead of deriving an observa-
tion from its explanation, we derive the explanation from the observation.
That a hypothesis provides the best explanation of something whose truth
is already known provides evidence for the truth of that hypothesis.
Once we grasp the notion of an inference to the best explanation, we
can see this pattern of reasoning everywhere. If you see your friend kick
the wall, you infer that he must be angry, because there is no other expla-
nation of why he would kick the wall. Then if he turns away when you
say, “Hello,” you might think that he is angry at you, if you cannot im-
agine any other reason why he would not respond. Similarly, when your
car goes dead right after a checkup, you may conclude that it is out of
fuel, if that is the best explanation of why your car stopped. Psycholo-
gists infer that people care what others think about them, even when they
deny it, because that explains why people behave differently in front of
others than when they are alone. Linguists argue that the original Indo-
European language arose millennia ago in an area that was not next to
the sea but did have lakes and rivers, because that is the best explanation
of why Indo-European languages have no common word for seas but do
share a common root “nav-” that connotes boats or ships. Astronomers
believe that our Universe began with a Big Bang, because that hypothesis
best explains the background microwave radiation and spreading of gal-
axies. All of these arguments and many more are basically inferences to
the best explanation.
Solutions to murder mysteries almost always have the form of an infer-
ence to the best explanation. The facts of the case are laid out and then the
clever detective argues that, given these facts, only one person could possi-
bly have committed the crime. In the story “Silver Blaze,” Sherlock Holmes
concludes that the trainer must have been the dastardly fellow who stole
Silver Blaze, the horse favored to win the Wessex Cup, which was to be run
the following day. Holmes’s reasoning, as usual, was very complex, but the
key part of his argument was that the dog kept in the stable did not bark
loudly when someone came and took away the horse.
I had grasped the significance of the silence of the dog, for one true inference
invariably suggests others. [I knew that] a dog was kept in the stables, and yet,
though someone had been in and fetched out a horse, he had not barked enough
to arouse the two lads in the loft. Obviously the midnight visitor was someone
whom the dog knew well.^297364_ch09_ptg01_195-214.indd 197 15/11/13 10:47 AM
some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materiallyCopyright 201^3 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights,
affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.