No, that is not how it works: I don't need to either accept or reject MWI. I can also treat it as a causal story lacking empirical content.
To say that MWI lacks empirical content is also to say that the negation of MWI lacks empirical content. So this doesn't tell us, for example, whether to assign higher probability to MWI or to the disjunction of all non-MWI interpretations.
Suppose your ancestors sent out a spaceship eons ago, and by your calculations it recently traveled so far away that no physical process could ever cause you and the spaceship to interact again. If you then want to say that 'the claim the spaceship still exists lacks empirical content,' then OK. But you will also have to say 'the claim the spaceship blipped out of existence when it traveled far enough away lacks empirical content'.
And there will still be some probability, given the evidence, that the spaceship did vs. didn't blip out of existence; and just saying 'it lacks empirical content!' will not tell you whether to design future spaceships so that their life support systems keep operating past the point of no return.
By that logic, if I invent any crazy hypothesis in addition to an empirically testable theory, then it inherits testability just on those grounds. You can do that with the word "testabiity" if you want, but that seems to be not how people use words.
There's no ambiguity if you clarify whether you're talking about the additional crazy hypothesis, vs. talking about the conjunction 'additional crazy hypothesis + empirically testable theory'. Presumably you're imagining a scenario where the conjunction taken as a whole is testable, though one of the conjuncts is not. So just say that.
Sean Carroll summarizes collapse-flavored QM as the conjunction of these five claims:
Quantum states are represented by wave functions, which are vectors in a mathematical space called Hilbert space.
Wave functions evolve in time according to the Schrödinger equation.
The act of measuring a quantum system returns a number, known as the eigenvalue of the quantity being measured.
The probability of getting any particular eigenvalue is equal to the square of the amplitude for that eigenvalue.
After the measurement is performed, the wave function “collapses” to a new state in which the wave function is localized precisely on the observed eigenvalue (as opposed to being in a superposition of many different possibilities).
Many-worlds-flavored QM, on the other hand, is the conjunction of 1 and 2, plus the negation of 5 -- i.e., it's an affirmation of wave functions and their dynamics (which effectively all physicists agree about), plus a rejection of the 'collapses' some theorists add to keep the world small and probabilistic. (If you'd like, you could supplement 'not 5' with 'not Bohmian mechanics'; but for present purposes we can mostly lump Bohm in with multiverse interpretations, because Eliezer's blog series is mostly about rejecting collapse rather than about affirming a particular non-collapse view.)
If we want 'QM' to be the neutral content shared by all these interpretations, then we can say that QM is simply the conjunction of 1 and 2. You are then free to say that we should assign 50% probability to claim 5, and maintain agnosticism between collapse and non-collapse views. But realize that, logically, either collapse or its negation does have to be true. You can frame denying collapse as 'positing invisible extra worlds', but you can equally frame denying collapse as 'skepticism about positing invisible extra causal laws'.
Since every possible way the universe could be adds something 'extra' on top of what we observe -- either an extra law (e.g., collapse) or extra ontology (because there are no collapses occurring to periodically annihilate the ontology entailed by the Schrodinger equation) -- it's somewhat missing the point to attack any given interpretation for the crime of positing something extra. The more relevant question is just whether simplicity considerations or indirect evidence helps us decide which 'something extra' (a physical law, or more 'stuff', or both) is the right one. If not, then we stick with a relatively flat prior.
Claims 1 and 2 are testable, which is why we were able to acquire evidence for QM in the first place. Claim 5 is testable for pretty much any particular 'collapse' interpretation you have in mind; which means the negation of claim 5 is also testable. So all parts of bare-bones MWI are testable (though it may be impractical to run many of the tests), as long as we're comparing MWI to collapse and not to Bohmian Mechanics.
(You can, of course, object that affirming 3-5 as fundamental laws has the advantage of getting us empirical adequacy. But 'MWI (and therefore also 'bare' QM) isn't empirically adequate' is a completely different objection from 'MWI asserts too many unobserved things', and in fact the two arguments are in tension: it's precisely because Eliezer isn't willing to commit himself to a mechanism for the Born probabilities in the absence of definitive evidence that he's sticking to 'bare' MWI and leaving almost entirely open how these relate to the Born rule. In the one case you'd be criticizing MWI theorists for refusing to stick their neck out and make some guesses about which untested physical laws and ontologies are the real ones; in the other case you'd be criticizing MWI theorists for making guesses about which untested physical laws and ontologies are the real ones.)
I am not super interested in having catholic theologians read about minimum descriptive complexity, and then weaving a yarn about their favorite hypotheses based on that.
Are you kidding? I would love it if theologians stopped hand-waving about how their God is 'ineffably simple no really we promise' and started trying to construct arguments that God (and, more importantly, the package deal 'God + universe') is information-theoretically simple, e.g., by trying to write a simple program that outputs Biblical morality plus the laws of physics. At best, that sort of precision would make it much clearer where the reasoning errors are; at worst, it would be entertainingly novel.
Many-worlds-flavored QM, on the other hand, is the conjunction of 1 and 2, plus the negation of 5
Plus 6: There is a preferred basis.
You are unlikely to see me posting here again, after today. There is a saying here that politics is the mind-killer. My heretical realization lately is that philosophy, as generally practiced, can also be mind-killing.
As many of you know I am, or was running a twice-monthly Rationality: AI to Zombies reading group. One of the bits I desired to include in each reading group post was a collection of contrasting views. To research such views I've found myself listening during my commute to talks given by other thinkers in the field, e.g. Nick Bostrom, Anders Sandberg, and Ray Kurzweil, and people I feel are doing “ideologically aligned” work, like Aubrey de Grey, Christine Peterson, and Robert Freitas. Some of these were talks I had seen before, or generally views I had been exposed to in the past. But looking through the lens of learning and applying rationality, I came to a surprising (to me) conclusion: it was philosophical thinkers that demonstrated the largest and most costly mistakes. On the other hand, de Grey and others who are primarily working on the scientific and/or engineering challenges of singularity and transhumanist technologies were far less likely to subject themselves to epistematic mistakes of significant consequences.
Philosophy as the anti-science...
What sort of mistakes? Most often reasoning by analogy. To cite a specific example, one of the core underlying assumption of singularity interpretation of super-intelligence is that just as a chimpanzee would be unable to predict what a human intelligence would do or how we would make decisions (aside: how would we know? Were any chimps consulted?), we would be equally inept in the face of a super-intelligence. This argument is, however, nonsense. The human capacity for abstract reasoning over mathematical models is in principle a fully general intelligent behaviour, as the scientific revolution has shown: there is no aspect of the natural world which has remained beyond the reach of human understanding, once a sufficient amount of evidence is available. The wave-particle duality of quantum physics, or the 11-dimensional space of string theory may defy human intuition, i.e. our built-in intelligence. But we have proven ourselves perfectly capable of understanding the logical implications of models which employ them. We may not be able to build intuition for how a super-intelligence thinks. Maybe—that's not proven either. But even if that is so, we will be able to reason about its intelligent behaviour in advance, just like string theorists are able to reason about 11-dimensional space-time without using their evolutionarily derived intuitions at all.
This post is not about the singularity nature of super-intelligence—that was merely my choice of an illustrative example of a category of mistakes that are too often made by those with a philosophical background rather than the empirical sciences: the reasoning by analogy instead of the building and analyzing of predictive models. The fundamental mistake here is that reasoning by analogy is not in itself a sufficient explanation for a natural phenomenon, because it says nothing about the context sensitivity or insensitivity of the original example and under what conditions it may or may not hold true in a different situation.
A successful physicist or biologist or computer engineer would have approached the problem differently. A core part of being successful in these areas is knowing when it is that you have insufficient information to draw conclusions. If you don't know what you don't know, then you can't know when you might be wrong. To be an effective rationalist, it is often not important to answer “what is the calculated probability of that outcome?” The better first question is “what is the uncertainty in my calculated probability of that outcome?” If the uncertainty is too high, then the data supports no conclusions. And the way you reduce uncertainty is that you build models for the domain in question and empirically test them.
The lens that sees its own flaws...
Coming back to LessWrong and the sequences. In the preface to Rationality, Eliezer Yudkowsky says his biggest regret is that he did not make the material in the sequences more practical. The problem is in fact deeper than that. The art of rationality is the art of truth seeking, and empiricism is part and parcel essential to truth seeking. There's lip service done to empiricism throughout, but in all the “applied” sequences relating to quantum physics and artificial intelligence it appears to be forgotten. We get instead definitive conclusions drawn from thought experiments only. It is perhaps not surprising that these sequences seem the most controversial.
I have for a long time been concerned that those sequences in particular promote some ungrounded conclusions. I had thought that while annoying this was perhaps a one-off mistake that was fixable. Recently I have realized that the underlying cause runs much deeper: what is taught by the sequences is a form of flawed truth-seeking (thought experiments favored over real world experiments) which inevitably results in errors, and the errors I take issue with in the sequences are merely examples of this phenomenon.
And these errors have consequences. Every single day, 100,000 people die of preventable causes, and every day we continue to risk extinction of the human race at unacceptably high odds. There is work that could be done now to alleviate both of these issues. But within the LessWrong community there is actually outright hostility to work that has a reasonable chance of alleviating suffering (e.g. artificial general intelligence applied to molecular manufacturing and life-science research) due to concerns arrived at by flawed reasoning.
I now regard the sequences as a memetic hazard, one which may at the end of the day be doing more harm than good. One should work to develop one's own rationality, but I now fear that the approach taken by the LessWrong community as a continuation of the sequences may result in more harm than good. The anti-humanitarian behaviors I observe in this community are not the result of initial conditions but the process itself.
What next?
How do we fix this? I don't know. On a personal level, I am no longer sure engagement with such a community is a net benefit. I expect this to be my last post to LessWrong. It may happen that I check back in from time to time, but for the most part I intend to try not to. I wish you all the best.
A note about effective altruism…
One shining light of goodness in this community is the focus on effective altruism—doing the most good to the most people as measured by some objective means. This is a noble goal, and the correct goal for a rationalist who wants to contribute to charity. Unfortunately it too has been poisoned by incorrect modes of thought.
Existential risk reduction, the argument goes, trumps all forms of charitable work because reducing the chance of extinction by even a small amount has far more expected utility than would accomplishing all other charitable works combined. The problem lies in the likelihood of extinction, and the actions selected in reducing existential risk. There is so much uncertainty regarding what we know, and so much uncertainty regarding what we don't know that it is impossible to determine with any accuracy the expected risk of, say, unfriendly artificial intelligence creating perpetual suboptimal outcomes, or what effect charitable work in the area (e.g. MIRI) is have to reduce that risk, if any.
This is best explored by an example of existential risk done right. Asteroid and cometary impacts is perhaps the category of external (not-human-caused) existential risk which we know the most about, and have done the most to mitigate. When it was recognized that impactors were a risk to be taken seriously, we recognized what we did not know about the phenomenon: what were the orbits and masses of Earth-crossing asteroids? We built telescopes to find out. What is the material composition of these objects? We built space probes and collected meteorite samples to find out. How damaging an impact would there be for various material properties, speeds, and incidence angles? We built high-speed projectile test ranges to find out. What could be done to change the course of an asteroid found to be on collision course? We have executed at least one impact probe and will monitor the effect that had on the comet's orbit, and have on the drawing board probes that will use gravitational mechanisms to move their target. In short, we identified what it is that we don't know and sought to resolve those uncertainties.
How then might one approach an existential risk like unfriendly artificial intelligence? By identifying what it is we don't know about the phenomenon, and seeking to experimentally resolve that uncertainty. What relevant facts do we not know about (unfriendly) artificial intelligence? Well, much of our uncertainty about the actions of an unfriendly AI could be resolved if we were to know more about how such agents construct their thought models, and relatedly what language were used to construct their goal systems. We could also stand to benefit from knowing more practical information (experimental data) about in what ways AI boxing works and in what ways it does not, and how much that is dependent on the structure of the AI itself. Thankfully there is an institution that is doing that kind of work: the Future of Life institute (not MIRI).
Where should I send my charitable donations?
Aubrey de Grey's SENS Research Foundation.
100% of my charitable donations are going to SENS. Why they do not get more play in the effective altruism community is beyond me.
If you feel you want to spread your money around, here are some non-profits which have I have vetted for doing reliable, evidence-based work on singularity technologies and existential risk:
I wish I could recommend a skepticism, empiricism, and rationality promoting institute. Unfortunately I am not aware of an organization which does not suffer from the flaws I identified above.
Addendum regarding unfinished business
I will no longer be running the Rationality: From AI to Zombies reading group as I am no longer in good conscience able or willing to host it, or participate in this site, even from my typically contrarian point of view. Nevertheless, I am enough of a libertarian that I feel it is not my role to put up roadblocks to others who wish to delve into the material as it is presented. So if someone wants to take over the role of organizing these reading groups, I would be happy to hand over the reigns to that person. If you think that person should be you, please leave a reply in another thread, not here.
EDIT: Obviously I'll stick around long enough to answer questions below :)