Privileging the Hypothesis

Eliezer Yudkowsky29 Sep 2009 0:40 UTC
125 points
130 comments5 min readLW linkArchive

Suppose that the police of Largeville, a town with a million inhabitants, are investigating a murder in which there are few or no clues—the victim was stabbed to death in an alley, and there are no fingerprints and no witnesses.

Then, one of the detectives says, “Well… we have no idea who did it… no particular evidence singling out any of the million people in this city… but let’s consider the hypothesis that this murder was committed by Mortimer Q. Snodgrass, who lives at 128 Ordinary Ln. It could have been him, after all.”

I’ll label this the fallacy of privileging the hypothesis. (Do let me know if it already has an official name—I can’t recall seeing it described.)

Now the detective may perhaps have some form of rational evidence that is not legal evidence admissible in court—hearsay from an informant, for example. But if the detective does not have some justification already in hand for promoting Mortimer to the police’s special attention—if the name is pulled entirely out of a hat—then Mortimer’s rights are being violated.

And this is true even if the detective is not claiming that Mortimer “did” do it, but only asking the police to spend time pondering that Mortimer might have done it—unjustifiably promoting that particular hypothesis to attention. It’s human nature to look for confirmation rather than disconfirmation. Suppose that three detectives each suggest their hated enemies, as names to be considered; and Mortimer is brown-haired, Frederick is black-haired, and Helen is blonde. Then a witness is found who says that the person leaving the scene was brown-haired. “Aha!” say the police. “We previously had no evidence to distinguish among the possibilities, but now we know that Mortimer did it!”

This is related to the principle I’ve started calling “locating the hypothesis,” which is that if you have a billion boxes only one of which contains a diamond (the truth), and your detectors only provide 1 bit of evidence apiece, then it takes much more evidence to promote the truth to your particular attention—to narrow it down to ten good possibilities, each deserving of our individual attention—than it does to figure out which of those ten possibilities is true. It takes 27 bits to narrow it down to ten, and just another 4 bits will give us better than even odds of having the right answer.

Thus the detective, in calling Mortimer to the particular attention of the police, for no reason out of a million other people, is skipping over most of the evidence that needs to be supplied against Mortimer.

And the detective ought to have this evidence in their possession, at the first moment when they bring Mortimer to the police’s attention at all. It may be mere rational evidence rather than legal evidence, but if there’s no evidence then the detective is harassing and persecuting poor Mortimer.

During my recent diavlog with Scott Aaronson on quantum mechanics, I did manage to corner Scott to the extent of getting Scott to admit that there was no concrete evidence whatsoever that favors a collapse postulate or single-world quantum mechanics. But, said Scott, we might encounter future evidence in favor of single-world quantum mechanics, and many-worlds still has the open question of the Born probabilities.

This is indeed what I would call the fallacy of privileging the hypothesis. There must be a trillion better ways to answer the Born question without adding a collapse postulate that would be the only non-linear, non-unitary, discontinous, non-differentiable, non-CPT-symmetric, non-local in the configuration space, Liouville’s-Theorem-violating, privileged-space-of-simultaneity-possessing, faster-than-light-influencing, acausal, informally specified law in all of physics. Something that unphysical is not worth saying out loud or even thinking about as a possibilitywithout a rather large weight of evidence—far more than the current grand total of zero.

But because of a historical accident, collapse postulates and single-world quantum mechanics are indeed on everyone’s lips and in everyone’s mind to be thought of, and so the open question of the Born probabilities is offered up (by Scott Aaronson no less!) as evidence that many-worlds can’t yet offer a complete picture of the world. Which is taken to mean that single-world quantum mechanics is still in the running somehow.

In the minds of human beings, if you can get them to think about this particular hypothesis rather than the trillion other possibilities that are no more complicated or unlikely, you really have done a huge chunk of the work of persuasion. Anything thought about is treated as “in the running,” and if other runners seem to fall behind in the race a little, it’s assumed that this runner is edging forward or even entering the lead.

And yes, this is just the same fallacy committed, on a much more blatant scale, by the theist who points out that modern science does not offer an absolutely complete explanation of the entire universe, and takes this as evidence for the existence of Jehovah. Rather than Allah, the Flying Spaghetti Monster, or a trillion other gods no less complicated—never mind the space of naturalistic explanations!

To talk about “intelligent design” whenever you point to a purported flaw or open problem in evolutionary theory is, again, privileging the hypothesis—you must have evidence already in hand that points to intelligent design specifically in order to justify raising that particular idea to our attention, rather than a thousand others.

So that’s the sane rule. And the corresponding anti-epistemology is to talk endlessly of “possibility” and how you “can’t disprove” an idea, to hope that future evidence may confirm it without presenting past evidence already in hand, to dwell and dwell on possibilities without evaluating possibly unfavorable evidence, to draw glowing word-pictures of confirming observations that could happen but haven’t happened yet, or to try and show that piece after piece of negative evidence is “not conclusive.”

Just as Occam’s Razor says that more complicated propositions require more evidence to believe, more complicated propositions also ought to require more work to raise to attention. Just as the principle of burdensome details requires that each part of a belief be separately justified, it requires that each part be separately raised to attention.

As discussed in Perpetual Motion Beliefs, faith and type 2 perpetual motion machines (water ice cubes electricity) have in common that they purport to manufacture improbability from nowhere, whether the improbability of water forming ice cubes or the improbability of arriving at correct beliefs without observation. Sometimes most of the anti-work involved in manufacturing this improbability is getting us to pay attention to an unwarranted belief—thinking on it, dwelling on it. In large answer spaces, attention without evidence is more than halfway to belief without evidence.

Someone who spends all day thinking about whether the Trinity does or does not exist, rather than Allah or Thor or the Flying Spaghetti Monster, is more than halfway to Christianity. If leaving, they’re less than half departed; if arriving, they’re more than halfway there.

An oft-encountered mode of privilege is to try to make uncertainty within a space, slop outside of that space onto the privileged hypothesis. For example, a creationist seizes on some (allegedly) debated aspect of contemporary theory, argues that scientists are uncertain about evolution, and then says, “We don’t really know which theory is right, so maybe intelligent design is right.” But the uncertainty is uncertainty within the realm of naturalistic theories of evolution—we have no reason to believe that we’ll need to leave that realm to deal with our uncertainty, still less that we would jump out of the realm of standard science and land on Jehovah in particular. That is privileging the hypothesis—taking doubt within a normal space, and trying to slop doubt out of the normal space, onto a privileged (and usually discredited) extremely abnormal target.

Similarly, our uncertainty about where the Born statistics come from should be uncertainty within the space of quantum theories that are continuous, linear, unitary, slower-than-light, local, causal, naturalistic, et cetera—the usual character of physical law. Some of that uncertainty might slop outside the standard space onto theories that violate one of these standard characteristics. It’s indeed possible that we might have to think outside the box. But single-world theories violate all these characteristics, and there is no reason to privilege that hypothesis.

Eliezer Yudkowsky29 Sep 2009 0:40 UTC
125 points
130 comments5 min readLW linkArchive