‘But…but…it’s the best available explanation!’ part 2

October 12, 2016

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In the previous post I pointed out that while argument to the best explanation is a legitimate form of inference used even by scientists, it's often also the first port of call of those who believe in conspiracy theories, miracles, and other wacky stuff. Let's now take a look at what can go wrong with arguments to the best explanation.


Suppose I can't find my keys. I was sure I left them by the door. Then I find them on the mantelpiece. I'm baffled - I just can't explain how they ended up where they did. My friend then suggests the following:


'Your house has gremlins! Think about it - such tricksy beings would want to hide your keys, wouldn't they? And they'd have the power to do it, too. So the existence of gremlins in your house would neatly explain how your keys ended up where they did. Gremlins explain what you can't otherwise explain! So gremlins are currently the best available explanation for the disappearance of your keys! So you should believe in gremlins!'


Is this a good argument for the existence of gremlins? Surely not. But what's wrong with it?


Well, while gremlins would indeed neatly explain what happened to my keys - something I am indeed struggling to explain - the probability remains much higher that some other much more mundane explanation is correct. True enough, I don't remember putting my keys on the mantelpiece, but maybe I did. My memory is very good, but occasionally I get things wrong. Or perhaps someone else entered the room moved the keys while I wasn't looking. Neither of these explanations might strike us as very likely, but that some such mundane explanation is correct is remains far more likely than that gremlins moved my keys. For we know that people do sometimes misremember, play tricks on each other, and so on; whereas we have very little evidence for, and considerable evidence against, the existence of gremlins.


Just because I don't know, and indeed can't come up with a plausible-sounding explanation of, how my keys ended up on the mantelpiece obviously doesn't justify me in supposing gremlins put them there.


Precisely what's gone wrong in such cases can vary, but as a general rule, (a) while fraud, or hallucination, or some other mundane explanation might in each case seem pretty unlikely, the fact is, we know these things do nevertheless happen (frauds do occur, people do have astonishing hallucinations, etc. etc.), and (b) there's typically little if any evidence for the existence of the mysterious beings other than such anecdotes, and indeed there's often also a great deal of evidence against their existence (e.g. in the gremlins case: if they existed then we'd expect to occasionally spot them lurking under the floorboards; how could they survive (on what food, etc?); why have they never been photographed of caught on CCTV, etc.?)


Thus, on balance, it's much more likely that some sort of fraud, or hallucination, etc. happened, even if, as a matter of fact, no especially plausible particular explanation is forthcoming. I'll unpack (a) more in the following post.


For an interesting case study, see William Lane Craig's The Resurrection of Jesus here. Craig says:

In summary, there are four facts agreed upon by the majority of scholars who have written on these subjects which any adequate historical hypothesis must account for: Jesus’ entombment by Joseph of Arimathea, the discovery of his empty tomb, his post-mortem appearances, and the origin of the disciples’ belief in his resurrection.

Now the question is: what is the best explanation of these four facts? Most sholars probably remain agnostic about this question. But the Christian can maintain that the hypothesis that best explains these facts is “God raised Jesus from the dead.”

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