Comment by mitchell_porter2 on Another Call to End Aid to Africa · 2009-04-04T05:13:32.000Z · LW · GW

"Her book ... asserts a direct cause-and-effect relationship between $1 trillion of aid and the rise in African poverty rates from 11% to 66%."

I have hardly skimmed the book but it does not appear to address the economic impact of population growth. Chapter 1 mentions that half of Africa is under the age of 15, but only so as to highlight the sheer number of young Africans lacking opportunities found elsewhere in the world. Wikipedia, paraphrasing UN estimates: "The total population of Africa is estimated at 922 million (as of 2005). It has doubled over the past 28 years, and has quadrupled over the past 55 years". It is still the fastest growing region on Earth, projected to double again by 2036.

I also see in Chapter 3 a remark about US aid to South Korea from the 1950s to the 1980s equalling all the aid that Africa has received (ever? from everyone? it's not clear, no source is given). South Korea is one of the most advanced countries in the world now.

It is almost certainly not the case that her "whole continent [was] wrecked by emotion and pity". The majority of the wasted or harmful aid would have been made by governments, many of them the former colonial masters, and with many conditions attached. I would think private aid is a very small part of the picture (so saying that "Celebrities at parties must be made ashamed to confess their donations to Africa" is wrongheaded). In another interview she mentions as a good channel for private donation.

The current hope for Africa seems to be trade with China (and, I would think, with the other new powers like Brazil and India), which gets a chapter in her book.

Comment by mitchell_porter2 on Formative Youth · 2009-02-25T03:02:38.000Z · LW · GW

Childhood is formative, being a teenager is formative, being a young adult is formative, etc. And some of those phases will involve a conscious reversal of previous beliefs and dispositions. It may be difficult to generalize here.

Also, I doubt that many people think their life was "all steered by Incredibly Deep Wisdom and uncaused free will". For most people, life has involved surprises, external impositions, revelations of personal folly, and so on.

Comment by mitchell_porter2 on Cynical About Cynicism · 2009-02-18T11:27:45.000Z · LW · GW

frelkins - that might have been true of the original Cynical movement in antiquity, but that's not what the word means now, surely. Though perhaps even the common cynic has some trace of that will to live truthfully and that boredom with considerations of life, death, and happiness.

When I wrote my comment yesterday, this post seemed to be an idealist's gambit, designed to attenuate the impact of cynicism by associating it with status-seeking rather than with truth, and I wanted to produce an emphatic reminder of the reality of everything bad in life. Even as I wrote it, I knew I was deviating from cautious empiricism into aphoristic intuition, and was therefore at risk of producing propaganda rather than truth. Today I cannot be bothered trying to assess how true it is, but in the spirit of something-or-other, I thought I would at least note these psychological facts.

Comment by mitchell_porter2 on Cynical About Cynicism · 2009-02-17T05:10:43.000Z · LW · GW

Cynicism is fundamentally about self-defense from future pain. What is the basic message of a cynic? "You'll be disappointed." The cynic, having themselves been painfully disappointed by life, preempts a repeat of the experience by anticipating it everywhere they can, steering clear of hope in general, and advising others to do the same. Some cynics may seek the weakly compensating satisfaction of vanity by trying to perform their cynicism so as to impress, but that is not the essence of the attitude.

Comment by mitchell_porter2 on Three Worlds Decide (5/8) · 2009-02-04T02:37:00.000Z · LW · GW

The lesson I draw from this story is that in it, the human race went to the stars too soon. If they had thought more about situations like this before they started travelling the starlines, they'd have a prior consensus about what to do.

Comment by mitchell_porter2 on Failed Utopia #4-2 · 2009-01-22T03:20:00.000Z · LW · GW

This is what I think of as a "mildly unfriendly" outcome. People still end up happy, but before the change, they would not have wanted the outcome. One way for that to happen involves the AI forcibly changing value systems, so that everyone suddenly has an enthusiasm for whatever imperatives it wishes to impose. In this story, as I understand it, there isn't even alteration of values, just a situation constructed to induce the victory of one set of values (everything involved in the quest for a loved one) over another set of values (fidelity to the existing loved one), in a way which violates the protagonist's preferred hierarchy of values.

Comment by mitchell_porter2 on My Kind of Reflection · 2008-07-11T05:23:14.000Z · LW · GW

With respect to reflective decision theory: a few weeks ago I saw a talk by economist Jason Potts on the "economics of identity". Apparently there is a small literature now - Nobel laureate George Akerlof was mentioned - examining the effects of identity-dependent utility functions, where one's "identity" is something like "one's currently dominant self-concept". Jason described the existing work as static, and said he had a paper coming out which would introduce a dynamic account - I got the impression of something like Tom McCabe's self-referential agent.

Comment by mitchell_porter2 on I'd take it · 2008-07-03T04:39:09.000Z · LW · GW

Whereas for the US federal government, the question is "So if you owed $10 trillion, what would you do about it?"

That's about 15% of gross world product, by the way.

Comment by mitchell_porter2 on The Ultimate Source · 2008-06-19T01:58:00.000Z · LW · GW

Caledonian: "I didn't say it was completely unreliable. I said it was completely useless."

I'm surprised you didn't take my second option and moderate your position. Whether you are insisting that introspection is only ever accurate by coincidence, or just that whatever accuracy it possesses is of no practical utility, neither position bears much relationship to reality. The introspective modalities, however it is that they are best characterized, have the same quality - partial reliability - that you attributed to the external senses, and everyone uses them every day to get things done, and in doing so they are not just rolling dice.

Even the argument that a capacity for accurate self-representation has never been selected for is questionable, in a social primate which uses language to communicate and coordinate.

Comment by mitchell_porter2 on The Ultimate Source · 2008-06-18T01:47:00.000Z · LW · GW

Caledonian, the science of physiology and evolution may have played a large role in the creation of your epistemology, but I don't doubt that you also personally thought about the issues, paid attention to your own thinking to see if you were making mistakes, and so forth. Anyway, there's no need to play the reflexive game of "you would have used introspection on your way to the conclusion that introspection can't be used", in order to combat the notion that introspection is completely unreliable. If it were completely unreliable you would never be accurate even when reporting your own opinions, except perhaps by chance.

You might be able to defend your position by saying that all partly reliable self-knowledge comes through sensory, quasi-sensory and proto-sensory modalities, and that it's only a specific sort of self-"perception" that is 100% unreliable.

Comment by mitchell_porter2 on The Ultimate Source · 2008-06-17T12:48:52.000Z · LW · GW

Caledonian, the trouble with denying any validity at all to introspective perception is that it would imply that consciousness plays no role in valid cognition. And yet consider the elaborate degree of self-consciousness implied by the construction of the epistemology you just articulated! Are you really going to say you derived all that purely from sense perception and unconscious cognition, with no input from conscious reflection?

Comment by mitchell_porter2 on The Ultimate Source · 2008-06-17T11:43:10.000Z · LW · GW

Caledonian: "Our perceptions, and most especially our mental self-perceptions, are not veridical. Once we acknowledge that we do not need to [do stuff]"

Do you think "our perceptions, and most especially our mental self-perceptions" are completely valueless? If not, where do you draw the line between valid and invalid?

Comment by mitchell_porter2 on Causality and Moral Responsibility · 2008-06-14T04:46:37.000Z · LW · GW

Allan Crossman: "If a machine can be consistently interpreted as "doing addition", doesn't that indicate that there are intrinsic facts about the machine that have something to do with addition?"

The same physical process, as a computation, can have entirely different semantics depending on interpretation. That already tells you that none of those interpretations is intrinsic to the physical process.

Caledonian: "We don't need a mind to perceive meaning in a pattern of electrical impulses generated by a circuit for that circuit to perform arithmetic. As long as the circuit enforces the correct relationship between input and output values, it implements the mathematical operation defined by that relationship."

See previous comment. There is a physical relationship between inputs and outputs, and then there is a plethora of mathematical (and other) relationships which can be mapped onto the physical relationship.

One may as well say that the words in a natural language intrinsically have certain meanings. If that were true, it would literally be impossible to utilize them in some inverted or nonstandard way, which is false.

Comment by mitchell_porter2 on Causality and Moral Responsibility · 2008-06-13T10:37:35.000Z · LW · GW

Artificial addition is not intrinsically addition, any more than a particular string of shapes on a page intrinsically means anything. There is no "structure that is addition", but there are "structures" that can represent addition.

What is addition, primordially? The root concept is one of combination or juxtaposition of actual entities. The intellectual process consists of reasoning about and identifying the changes in quantity that result from such juxtaposition. And artificial addition is anything that allows one to skip some or all of the actual reasoning, and proceed directly to the result.

Husserl's Logical Investigations has a lot about the phenomenology of arithmetic. That's where I'd go for a phenomenological ontology of addition. Ironically, through the exactness of its analyses the book played a distant role in launching cognitive science and the mechanization of thought, even while its metaphysics of mind was rejected.

The basic distinction is between intrinsic intentionality and derived intentionality. Thoughts have intrinsic intentionality, they are intrinsically about what they are about; words and "computations" have derived intentionality, they are convention-dependent assignments of meaning to certain physical things and processes. Artificial addition only has derived intentionality. If something has "the structure of addition", that means it can consistently be interpreted as implementing addition, not that it inherently does so.

The problem, of course, is that in the physical world it seems like nothing has intrinsic intentionality; everything is just a pile of atoms, nothing inherently refers to anything, nothing is inherently about anything. But there are causal relations, and so we have theories of meaning which try to reduce it to causal relations. B is about A if A has the right sort of effects on B. I think that's backwards, and superficial: if B is about A, that implies, among other things, than A has a certain causal relation to B, but the reverse does not hold. It's one of those things that needs a new ontology to be solved.

This perspective does not alter Eliezer's point. Even if thou art monadic intrinsic intentionality, rather than "physics", you're still something, and decisions still involve causation acting through you.

Comment by mitchell_porter2 on Quantum Physics Revealed As Non-Mysterious · 2008-06-13T06:33:29.000Z · LW · GW

To respond to the SEED article at slightly greater length... We can start by trying to get a grip on what they mean by "realism". Zeilinger himself says "to give up realism about the moon, that's ridiculous". So the so-called rejection of realism doesn't involve anything like the abandonment of belief in reality (whatever that could mean), just an abandonment of belief in the reality of some things. Calling that a rejection of realism may be rhetorical excess; it is as if I believed there was a cake in the cupboard, discovered there wasn't, and as a result proclaimed that realism about the cake had been falsified.

However, Zeilinger says, "on the quantum level we do have to give up realism". So what does that mean? We believe in things made of particles (like the moon), but not the particles themselves? We believe that big things, like the moon, have properties, but that small ones, like particles, do not? In the end, it seems we are to abandon the belief that small things have properties before we look. No, wait, we are to abandon the belief that small things have the properties we see them to have before we looked. Well, what if they had some other property before we looked, and then the act of looking (measuring, more precisely) perturbed them into a new state with new properties? That would seem to be entirely consistent with what they describe, but what does that have to do with the 'falsification of realism'?

Do I sound exasperated? Pardon me. It is just that there is so, so much nonsense propagated by physicists in the name of physics, and then further passed on by credulous people who are in no position to make an independent judgement about what they've been hearing. The situation is something like this: We have quantum mechanics, which works experimentally. Traditionally, the quantum states (wavefunctions) are not regarded as the fundamental reality of things, they're just a quasi-statistical description which happens to work. So, on the one hand, we have a variety of attempts to explain what the fundamental reality might actually be, and on the other hand, we have - complacency, basically. A frame of mind which is content to use QM as it is, apply it, extend it, but not to dig deeper. Returning to the attempts at a deeper explanation, we have, as SEED mentions, Bohm's theory, which is a nonlocal theory. So long as quantum mechanics continues to work experimentally, Bohm's theory will never be falsified, because it makes exactly the same predictions as quantum theory. On the other hand, Leggett apparently produced a nonlocal theory which does make slightly different predictions. Zeilinger's group did the experiments, quantum mechanics was right, Leggett was wrong - and this is trumpeted as a falsification of realism on the quantum level, for absolutely no good reason that I can see. It is, I suppose, a falsification of the particular postulates that Leggett was trying to uphold, but calling this a falsification of realism is like saying that not finding the cake in the cupboard was a falsification of realism.

Comment by mitchell_porter2 on Quantum Physics Revealed As Non-Mysterious · 2008-06-13T05:50:44.000Z · LW · GW

Brian M: the basic rule is that if a physicist says something which sounds like mysticism, solipsism, or irrationalism, you ignore it. They are occupational hazards for the philosophizing physicist; you are hearing the effects of a "workplace injury" and nothing more.

Comment by mitchell_porter2 on Quantum Mechanics and Personal Identity · 2008-06-13T03:47:58.000Z · LW · GW

Blogs have been turned into books before, e.g. Iraqi bloggers Salam Pax and Riverbend.

Comment by mitchell_porter2 on Against Devil's Advocacy · 2008-06-09T08:43:04.000Z · LW · GW

In high school I was on a debating team, and I can remember eventually forming the view that it was a potentially corrupting exercise, because you had to argue for the position you were given, not the position that you believed or the position that you might rationally favor. Occasionally the format permitted creative responses; I recall that once, the affirmative team had to argue 'That Australia has failed the Aborigine', and we on the negative team decided to outflank rather than straightforwardly oppose; we said that wasn't true because what Australia had done was much much worse than that. But even that was basically an exercise in lawyerly ingenuity, resulting from a desire to win rather than from a desire to arrive at the truth.

Comment by mitchell_porter2 on If Many-Worlds Had Come First · 2008-06-05T06:18:06.000Z · LW · GW

Meanwhile, imagine yet another alternate Earth, where the very first physicists to notice nonlocality, said, "Holy brachiating orangutans, there's a non-local force in Nature!"

In the years since, the theory has been successfully extended to encompass every observed phenomenon. The biggest mystery in physics is the relationship between nonlocality and relativity. The basic equations have a preferred reference frame, but it's undetectable. Everyone thinks that there must be a relativistic way to write the equations, but no-one knows how to do it.

One day, Bavid Dohm walks into the office of Huve Erett...

Bavid gestures to the paper he'd brought to Huve Erett. It is a short paper. The title reads, "The Solution to the Relativity Problem". The body of the paper reads:

"There is no classical trajectory. The pilot wave already contains the world that we see, along with infinitely many others."

"Let me make absolutely sure," Erett says carefully, "that I understand you. You're saying that there is no space-time, as we know it, separate from Hilbert space. There's just the pilot wave, evolving according to the Schrodinger equation. But the pilot wave actually contains space-time - infinitely many space-times."

"Right!" says Bavid.

"Where?" says Erett.

"Everywhere throughout configuration space!" says Bavid. "The configurations are the worlds."

"But if every possible configuration exists, how do you predict anything?" asks Erett.

"Er, well, it's not the configurations which are the worlds, then", says Bavid. "It's the blobs of amplitude hovering over the configurations."

"I still don't see how you make predictions. Or eliminate a universal time coordinate", says Erett.

"Decoherence!" says Bavid. "If you don't count the blobs where the amplitude really thins out, then the numbers come out correctly."

"But the blobs are still there?" asks Erett.

"Yes... they're just... thinner", says Bavid.

"Why shouldn't I count them, then?" asks Erett.

"Because the numbers won't come out right otherwise!" says Bavid.

"I see", says Erett. "And relativity? You did say this is a relativistic theory."

"Yes, well, my idea is to get rid of time entirely", says Bavid.

"Ah yes, the old 'H=0' approach. The pilot wave is a standing wave. But how is that relativistic? Relativity mingles space and time. H=0 just abolishes time and leaves space", says Erett.

"Er..." says Bavid.

At which point Erett politely but firmly shows Mr Dohm out of his office.

Comment by mitchell_porter2 on Living in Many Worlds · 2008-06-05T05:28:43.000Z · LW · GW

But the probability that anyone is immortal in any specific branch is basically zero. There is a nonzero probability of death per unit time, and so the probability of literal immortality is infinitesimal, being a product of infinitely many quantities less than 1.

Comment by mitchell_porter2 on Living in Many Worlds · 2008-06-05T05:24:18.000Z · LW · GW

Prakash, I thought the point of quantum immortality was that everyone is "immortal" because everyone has a duplicate who lives on, however improbably, in some branch of the wavefunction, no matter what happens here.

Comment by mitchell_porter2 on Why Quantum? · 2008-06-04T09:12:44.000Z · LW · GW

Stephen: consistent histories works by having a set of disjoint, coarse-grained histories - "coarse-grained" meaning that they are underspecified by classical standards - which then obtain a-priori probabilities through the use of a "decoherence functional" (which is where stuff like the Hamiltonian, that actually defines the theory, enters). You then get the transition probabilities of ordinary quantum mechanics by conditioning on those global probabilities of whole histories.

Some people have a neo-Copenhagenist attitude towards consistent histories - i.e., it's just a formalism - but if you take it seriously as a depiction of an actually existing ensemble of worlds, it's quite different from the more Parmenidean vision offered here, in which reality is a standing wave in configuration space, and "worlds" (and, therefore, observers) are just fuzzily defined substructures of that standing wave. The worlds in a realist consistent-histories interpretation would be sharply defined and noninteracting.

There is certainly a relation between the two possible versions of Many Worlds, in that you can construct a decoherence functional out of a wavefunction of the universe, and derive the probabilities of the coarse-grained histories from it. In effect, each history correponds to a chunk of configuration space, and the total probability of that history comes from the amplitudes occupying that chunk. (The histories do not need to cover all of configuration space; they only need to be disjoint.) ... I really need some terminology here. I'm going to call one type Parmenidean, and the other type Lewisian, after David Lewis, the philosopher who talked about causally disjoint multiple worlds. So: you can get a Lewisian theory of many worlds from a Parmenidean theory by breaking off chunks of the Parmenidean "block multiverse" and saying that those are the worlds. I can imagine a debate between a Parmenidean and a Lewisian, in which a Parmenidean would claim that their approach is superior because they regard all the possible Lewisian decompositions as equally partially real, whereas the Lewisian might argue that their approach is superior because there's no futzing around about what a "world" is - the worlds are clearly (albeit arbitrarily) defined.

But the really significant thing is that you can get the numerical quantum predictions from the "Lewisian" approach, but you can't get it from the Parmenidean. Robin Hanson's mangled worlds formula gets results by starting down the road towards a Lewisian specification of exactly what the worlds are, but he gets the right count in a certain limit without having to exactly specify when one world becomes two (or many). Anyway, the point is not that consistent histories makes different predictions, but that it makes predictions at all.

Comment by mitchell_porter2 on Why Quantum? · 2008-06-04T07:13:57.000Z · LW · GW

"The balance of arguments is overwhelmingly tipped; and physicists who deny it, are making specific errors of probability theory (which I have specifically laid out, and shown to you)"

I guess this refers to the error of supposing that Occam's Razor literally means "have as few entities as possible", rather than "have a theory as simple as possible", and opposing Many Worlds for that reason. Which is indeed an error.

But perhaps for the last time, I will try to enumerate those problems with your position that I can remember.

  1. There is no relativistic formulation of Many Worlds; you just trust that there is.

  2. There is no derivation of the Born probabilities, which contain all the predictive content of quantum mechanics.

  3. Robin Hanson has a proposal to derive the probabilities, but for now it rests on making vagueness about the concept of observers and worlds into a virtue.

You've given zero public consideration to other possibilities such as temporally bidirectional causation and nonsubjective collapse theories. You've also ignored Bohmian mechanics, a classically objective theory which does make all the predictions of quantum theory. You also haven't said anything about the one version of Many Worlds which does produce predictions - the version Gell-Mann favors, "consistent histories" - which has a distinctly different flavor to the "waves in configuration space" version.

In view of all that, how can you possibly say that Many Worlds is rationally favored, or that you have made a compelling case for this?

I'll repeat my earlier recommendation:

"What you should say as a neo-rationalist is that ... people should not be content with an incomplete description of the world, and that something like Minimum Description Length should be used to select between possible complete theories when there is nothing better, and you should leave it at that."

I wrote a little essay at Nick Tarleton's forum, here, about these problems. I will at some point link from there to my various comments posted here, so it's all in the one place. And I suppose eventually I'll have to write my own views out at length (not just my anti-MWI views). My main unexpressed view is that string theory is probably the answer, and that attempts to make ontological sense of physics will have to grapple with its details, and so all these other 'interpretations' are merely preliminary ideas that may at best be helpful in the real struggle.

Comment by mitchell_porter2 on Timeless Identity · 2008-06-03T10:01:57.000Z · LW · GW

Covalent bonds with external atoms are just one form of "correlation with the environment".

I wish to postulate a perfect copy, in the sense that the internal correlations are identical to the original, but in which the correlations to the rest of the universe are different (e.g. "on Mars" rather than "on Earth").

There is some confusion here in the switching between individual configurations, and configuration space. An atom is already a blob in configuration space (e.g. "one electron in the ground-state orbital") rather than a single configuration, with respect to a particle basis.

While we cannot individuate particles in a relative configuration, we can individuate wave packets traveling in relative configuration space. And since even an atom already exists at that level, it is far from clear to me that the attempt to abandon continuity of identity carries over to complicated structures.

Comment by mitchell_porter2 on Timeless Identity · 2008-06-03T09:47:00.000Z · LW · GW

Eliezer: That's how we distinguish Eliezer from Mitchell.

Isn't that then how we distinguish a nondestructive copy from the original? If the original has been copied nondestructively, why shouldn't we continue to regard it as the original?

Comment by mitchell_porter2 on Timeless Identity · 2008-06-03T09:23:53.000Z · LW · GW

The argument that "there is no such thing as a particular atom, therefore neither duplicate has a preferred status as the original" looks sophistical, and it may even be possible to show that it is within your preferred quantum framework. Consider a benzene ring. That's a ring of six carbon atoms. If it occurs as part of a larger molecule, there will be covalent bonds between particular atoms in the ring and atoms exterior to it. Now suppose I verify the presence of the benzene ring through some nondestructive procedure, and then create another benzene ring elsewhere, using other atoms. In fact, suppose I have a machine which will create that second benzene ring only if the investigative procedure verifies the existence of the first. I have created a copy, but are you really going to say there's no fact of the matter about which is the original? There's even a hint of how you can distinguish between the two given your ontological framework, when I stipulated that the original ring is bonded to something else; something not true of the duplicate. If you insist on thinking there is no continuity of identity of individual particles, at least you can say that one of the carbon atoms in the first ring is entangled with an outside atom in a way that none of the atoms in the duplicate ring is, and distinguish between them that way. You may be able to individuate atoms within structures by looking at their quantum correlations; you won't be able to say 'this atom has property X, that atom has property Y' but you'll be able to say 'there's an atom with property X, and there's an atom with property Y'.

Assuming that this is on the right track, the deeper reality is going to be field configurations anyway, not particle configurations. Particle number is frame-dependent (see: Unruh effect), and a quantum particle is just a sort of wavefunction over field configurations - a blob of amplitude in field configuration space.

Comment by mitchell_porter2 on Principles of Disagreement · 2008-06-02T08:37:45.000Z · LW · GW

But dammit, wavefunctions don't collapse!

Sorry to distract from your main point, but it is quite a distance from there to "therefore, there are Many Worlds". And for that matter, you have definitely not addressed the notion of collapse in all its possible forms. The idea of universe-wide collapse caused by observation is definitely outlandish, solipsistic in fact, and also leaves "consciousness", "observation", or "measurement" as an unanalysed residue. However, that's not the only way to introduce discontinuity into wavefunction evolution. One might have a jump (they won't be collapses, if you think in terms of state vectors) merely with respect to a particular subspace. The actual history of states of the universe might be a complicated agglomeration of quantum states, with spacelike joins provided by the tensor product, and timelike joins by a semilocal unitary evolution.

Furthermore, there have always been people who held that the wavefunction is only a representation of one's knowledge, and that collapse does not refer to an actual physical process. What you should say as a neo-rationalist is that those people should not be content with an incomplete description of the world, and that something like Minimum Description Length should be used to select between possible complete theories when there is nothing better, and you should leave it at that.

I suppose that the larger context is that in the case of seed AI, we need to get it right the first time, and therefore it would be helpful to have an example of rationality which doesn't just consist of "run the experiment and see what happens", in order to establish that it is possible to think about things in advance. But this is a bad example! Alas, I cannot call upon any intersubjective, third-party validation of this claim, but I do consider this (quantum ontology), if not my one true expertise, certainly a core specialization. And so I oppose my intuition to yours, and say that any valid completion of the Many Worlds idea is either going to have a simpler one-world variant, or, at best, it will be a theory of multiple self-contained worlds - not the splitting, half-merged, or otherwise interdependent worlds of standard MWI rhetoric. This is not a casual judgement; I could give a lengthy account of all the little reasons which lead up to it. If we had a showdown at the rationality dojo, I think it would come out the winner. But first of all, I think you should just ask yourself whether it makes sense to say "Many Worlds is the leading candidate" when all you have really shown is that a particular form of collapse theory is not.

Comment by mitchell_porter2 on A Premature Word on AI · 2008-06-01T06:08:00.000Z · LW · GW

Regarding the definition of "intelligence": It's not hard to propose definitions, if you assume the framework of computer science. Consider the cognitive architecture known as an "expected-utility maximizer". It has, to a first approximation, two parts. One part is the utility function, which offers a way of ranking the desirability of the situation which the entity finds itself in. The other part is the problem-solving part: it suggests actions, selected so as to maximize expected utility.

The utility function itself offers a way to rate the intelligence of different designs for the problem-solving component. You might, for example, average the utility obtained after a certain period of time across a set of test environments, or even across all possible environments. The point is that the EUM is supposed to be maximizing utility, and if one EUM is doing better than another, it must be because its problem-solver is more successful.

The next step towards rating the intrinsic intelligence of the problem-solving component is to compare its performance, not just across different environments, but when presented with different utility functions. Ideally, you would take into account how well it does under all possible utility functions, in all possible environments. (Since this is computer science, a "possible environment" will have a rather abstract definition, such as "any set of causally coupled finite-state machines".)

There are issues with respect to how you average; there are issues with respect to whether the "intelligence" you get from a definition like this is actually calculable. Nonetheless, those really are just details. The point is that there are rigorous ways to rank programs with respect to their ability to solve problems, and whether or not such a ranking warrants the name "intelligence", it is clearly of pragmatic significance. An accurate metric for the problem-solving capability of a goal-directed entity tells you how effective it will be in realizing those goals, and hence how much of an influence it can be in the world.

And this allows me to leap ahead and present a similarly informal account of what a Singularity is, what the problem of Friendliness is, and what the proposed solution is. A Singularity happens when naturally evolved intelligences, using the theory and technology of computation, create artificial intelligences of significantly superior problem-solving capability ("higher intelligence"). This superiority implies that in any conflict of goals, a higher intelligence wins against a lower intelligence (I'm speaking in general), because intelligence by definition is effectiveness in bringing about goal states. Since the goals of an artificial intelligence are thoroughly contingent (definitely so in the case of the EUM cognitive architecture), there is a risk to the natural intelligences that their own goals will be overwhelmed by those of the AIs; this is the problem of Friendliness. And the solution - at least, what I take to be the best candidate solution - is to determine the utility function (or its analogue) of the natural intelligences, determine the utility function of an ideal moral agent, relative to the preferences of that evolved utility function, and use that idealized utility function as the goal system of the artificial intelligences.

That, in schema, is my version of the research program of Eliezer's Institute. I wanted to spell it out because I think it's pretty easy to understand, and who knows how long it will be before Eliezer gets around to expounding it here, at length. It may be questioned from various angles; it certainly needs much more detail; but you have, right there, a formulation of what our situation is, and how to deal with it, which strikes me as eminently defensible and doable.

Comment by mitchell_porter2 on Class Project · 2008-05-31T10:39:15.000Z · LW · GW

Robin B., I can't speak for Eliezer's characters, but I believe the fashionability of skepticism about string theory has come from the lack of falsifiable predictions, after so many years. No-one has been able to say "this is the ground state". Instead string theorists have studied a large number of possible ground states (distinguished by background geometry), most of them looking nothing like what we see, as they try to get a grip on the theory. The hope used to be that all but one would prove on further study to be unstable. Now there's an interest in anthropic predictions, though that's just one school of thought.

I have read that no-one has ever exhibited a string-theory ground state exactly reproducing the Standard Model, though you can get close. That has to be significant. If such a place can be found in the space of ground states ("moduli space"), you could then try to reason out why it was dynamically favored. And we'll get more information within a few years from the Large Hadron Collider, which will establish whether there's a Higgs boson or something else (I bet on something else; the Higgs was just the simplest way to make a tractable theory and lingers by default).

In string theory's favor is that it generically has spin-1/2 particles (fermions), spin-1 particles (gauge bosons), and spin-2 particles (gravitons). That's a neat trick. So I tend to think either that it is the answer, or that it is just a beast of so many parts that anything you might look for is in there somewhere. In the latter case, it could be compared to the Monster group, the "largest sporadic simple finite group". There are infinitely many finite simple groups, just as there are infinitely many possible field theories, and most of those groups resemble some subgroup of the Monster, just as string theory has spin-1/2, spin-1, and spin-2 fields, just like the real world. It could be that string theory is just the "maximally complicated field theory" (and in fact, mathematically, it has a relationship to the Monster) and that it derives this generic pseudo-predictiveness solely from that. It has a little bit of everything, so anything looks a little bit like it. It would certainly be a mistake to take some real object, like Rubik's cube, discover a few facts about its symmetry group, and then announce that its symmetry group must be the Monster, just because the Monster has subgroups with those properties. It could be that string theorists are making a mistake like that.

On the other hand, what's the alternative? The phenomenological approach to particle physics is just to postulate enough fields with enough properties to explain what you see. You can treat gravity as just another field, contingently present, but then your theory becomes mathematically intractable. Part of string theory's appeal is that you can calculate graviton-graviton scattering, etc., unlike any previous theory of quantum gravity. But the price is that you buy into the unification philosophy. Recently, there have been claims that "contingent" theories of quantum gravity - according to which reality is just a bunch of fields plus gravity, and there's no deeper reason as to why it's that combination of fields - can be made to work; this is the "loop quantum gravity" research program. It's my judgement that string theory is mathematically much more solid. The loop quantum gravity researchers have had to backtrack several times, after making ambitious claims about the construction of consistent "gravity-plus-anything" quantum theories. Right now the evidence (in my semi-lay opinion) points in the other direction, that gravity needs to be part of a larger ensemble of fields with special properties if it is to be quantizable. Which suggests string theory.

Comment by mitchell_porter2 on Class Project · 2008-05-31T07:41:59.000Z · LW · GW

And on Day 26 they rediscovered string theory, and saw that it was good.

Comment by mitchell_porter2 on Einstein's Superpowers · 2008-05-30T08:18:42.000Z · LW · GW

If Einstein had chosen the wrong angle of attack on his problem - if he hadn't chosen a sufficiently important problem to work on - if he hadn't persisted for years - if he'd taken any number of wrong turns - or if someone else had solved the problem first - then dear Albert would have ended up as just another Jewish genius.

But if Einstein was the reason why none of those things happened, then maybe he wasn't just another Jewish genius, eh? Maybe he was smart enough to choose the right methods, to select the important problems, to see the value in persisting, to avoid or recover from all the wrong turns, and to be the first.

My own ruminations on genius have led me to suppose that one mistake which people of the very highest intelligence may make, is to underestimate their own exceptionality; for example, to adopt theories of human potential which are excessively optimistic regarding the capabilities of other people. But that is largely just my own experience speaking. It similarly seems very possible that the lessons you are trying to impart here are simply things you wish you hadn't had to figure out for yourself, but are not especially helpful or relevant for anyone else. In fact, I am reminded of one of my own pessimistic meta-principles regarding people of very high ability, which is that their situation will be so individual that no-one will be able to help them or understand them. It's not literally true, but it does point the way to the further conclusion that they will have to solve their own problems.

If anyone wants to see thoughts about genius they haven't seen before, they should first of all study the works and career of Celia Green. And then, as a side dish, they might like to read the chapter "Odysseus of Ithaca, by Kuno Mlatje", in Stanislaw Lem's A Perfect Vacuum.

Comment by mitchell_porter2 on Timeless Beauty · 2008-05-29T10:42:48.000Z · LW · GW

Erratum, I should have written "(quark disappears) (weak interaction happens) (antiquark appears)". My point is that the algebraic reversal of that expression is different from the time reversal of it, so those two parts of the Hamiltonian do actually say different things about the amplitude gradients in configuration space, even when you think about it "timelessly".

Comment by mitchell_porter2 on Timeless Beauty · 2008-05-29T10:38:59.000Z · LW · GW

I don't buy this abolition of time at all, but this question of how CP violation appears in Barbour's scheme seems like a good test of one's understanding.

The abolition of a time coordinate in quantum gravity is not Barbour's invention. The usual Schrodinger equation is Hψ = -i/hbar dψ/dt, where the H operator represents total energy (typically, sum of a potential and a kinetic term). But in general relativity, the total energy persistently shows up as zero (gravitational potential energy cancelling out against mass-energy, I believe; I confess I'm just relating this secondhand). So H=0, and there's no time evolution, just the stipulation that ψ has an H-eigenvalue of zero. Barbour's contribution is to offer an interpretation of configuration space as a set of "time capsules", static configurations containing static observers experiencing an illusion of time due to their memories. (I don't know what meaning Barbour ascribed to the amplitudes, and perhaps he has problems comparable to those suffered by the usual, timeful many worlds interpretation.) So that's it: H=0 gives you a standing wave in configuration space, and Barbour proposes a timeless variant on many worlds, with variables internal to the cosmic configuration, like cosmological radius, acting as clock variables, proxies for time.

Back to this CP violation problem. It is a theorem that quantum field theories have CPT symmetry, and it is an experimental result that CP symmetry is violated, i.e. that T symmetry is violated, in kaon-antikaon transitions. We actually have a quantum field theory implementing T-violation, the Standard Model, where it's implemented in the quark mass matrix. The numbers in that matrix would be coefficients of interaction terms in the potential-energy part of H, connecting quark fields and weak-boson fields, I think. It is something like postulating that the amplitude for (quark disappears) (weak interaction happens) (antiquark disappears) is different from the amplitude for (antiquark disappears) (weak interaction happens) (quark appears). In a sense it is quite unmysterious, since there is no mathematical barrier to postulating such an asymmetry, though one would like to know a deeper reason for it; the CPT theorem only says that if you transform those two processes by CPT, the amplitudes for the corresponding processes had better have the same relation.

Now formally it is a straightforward thing to take a quantum field theory and couple it to general relativity. For example, you can just take the QFT's old H, add a term for scalar curvature, and multiply the whole thing by "sqrt(determinant(metric))". Set the new H equal to zero, and you now have what should be the equation for a Standard Model universe with Einstein gravity thrown in; and though you probably can't solve that equation, you can still go ahead and follow Barbour's procedure in the resulting configuration space.

It seems obvious(?) that the expression of CP violation in the timeless picture will have something to do with those quark/antiquark fields in the CP-violating terms, and I would point out that although my informal description of those terms might seem to make one the time reverse of the other, actually there is an algebraic difference. Algebraically, "X appears" means that you use a "creation operator", while "X disappears" involves an "annihilation operator". So understanding the implications of those operators for amplitude gradients in the timeless picture may be the key to figuring this out. Also, since other physical variables act as clocks in the time capsules - proxies for an actual time - kaons and antikaons ought to somehow have a different relationship to the clock variables. If I was seriously trying to figure this out, I'd be thinking at the intersection of those two approaches. (And I'd be doing it using the simplest T-violating QFT I could find, rather than with the full Standard Model.) This is an excellent question to think about, for anyone trying to understand Barbour's interpretation in detail.

Comment by mitchell_porter2 on A Broken Koan · 2008-05-26T08:22:16.000Z · LW · GW

Caledonian, perhaps I should have written "objectivity-negating subjectivity" and "subjectivity-negating objectivity". The first would deny that reality has any intrinsic qualities (qualities independent of observation, basically), while the latter ends up denying the qualities of experience itself ("not even mind is moving").

frelkins, taking a stance in opposition to Nagarjuna is difficult because he's so neither-nor, but maybe just saying that something, somewhere, has an intrinsic nature is enough to do it. :-) You shouldn't read too much more into my remarks than that. I am agnostic on many points, and I am skeptical that anyone has ever yet known the truth about metaphysics. I have my preferred hypotheses, and I'm prepared to reject certain others, and that's about it.

Comment by mitchell_porter2 on A Broken Koan · 2008-05-25T07:13:34.000Z · LW · GW

frelkins: There's a story (which you may know) that Tibet held a debate between Indian Buddhists, who insisted that enlightenment can only be reached after many stages of analysis, and Chinese Buddhists, who said you could get there in one step. The Indians are said to have won the debate, but I was writing with the Chinese side in mind; I was trying to describe the path to nonduality in the most abbreviated way I could. I am aware of Nagarjuna and "codependent origination", and it may be that it was misleading of me to pass over that aspect. I welcome discussion and correction, though here may not be the place. (There is an unofficial Overcoming Bias forum here. Also, I'll mail you privately.) But, speaking mostly metaphorically, I favor Shankara over Nagarjuna. I believe in substances, essences, and a self. I think Buddhism is at the opposite extreme of error from the error of eliminative materialism - an all-negating subjectivity, rather than an all-negating objectivity - yet somehow complementary to it, as I suggested.

Comment by mitchell_porter2 on A Broken Koan · 2008-05-25T00:31:56.000Z · LW · GW

This love affair of modern rationalist materialists for Buddhism's metaphysical negations is peculiar in that the superficial similarities derive from completely different trains of thought. In a nutshell, as I understand it, the Buddhist argument (or a very prominent version) reduces all things to mind, by noticing the subjective element in all experience, and then reduces mind itself to ineffable formlessness by turning the argument on itself. By contrast, modern materialism in effect proceeds by substituting mathematics for subjectivity at every turn, until it reaches the point of saying that there is no subjectivity, only number (or whatever abstract category forms the basis of the preferred formalism).

I suppose the two approaches genuinely are potentially complementary, in that a Buddhist procedure could serve to make the scientific ontology subjectively plausible. But two wrongs don't make a right. We don't just think that time moves or that we are conscious; they are both quite real. At most it may be the case that the former is internal to the latter. But that is metaphysical idealism, not materialism or Buddhist relativism.

Comment by mitchell_porter2 on Do Scientists Already Know This Stuff? · 2008-05-19T03:19:50.000Z · LW · GW

Color isn't out there; but how can it be "in here", if the brain also just consists of particles in space? And color is either somewhere, or it's nowhere. Dennett takes the "nowhere" option, as part of his general denial of a "Cartesian theater", a place where appearances happen.

Except for those who think mental states can supervene directly on processes extending far outside the physical body, I think most scientifically minded people suppose that the world of appearance is somehow identical with something inside the brain: that (in one sense) what you see is in your visual cortex, even if (in another sense) what you see is far away. (Though they may prefer to say that it's the seeing that is in the cortex, rather than what is seen.) As I have just argued, this does not resolve the problem of locating perceived color (etc) in the physical world, it merely localizes the problem. We still await the identification of some physical thing or property in the brain which can plausibly be identified with an actual instance of color. And I think that's hopeless so long as you restrict yourself to states built up from fuzzy mesoscopic properties like membrane polarizations. The ghost of a homogeneous shade of color has to somehow hover over something which in actual fact consists of large numbers of ions on either side of a big macromolecule.

So I look for the true Cartesian theater to be found at a level where physically, even a 'particle' is just an approximation, such as in a decomposition of a global quantum state into what formally just appear to be algebraic structures lacking even a spatial interpretation. Quantum theory actually permits such an abstract perspective, if you step away from the use of a particular basis, such as configuration. I think that here, and only here, out of all the physics we know and half-know, is there something removed enough from spatializing presuppositions that it might be identifiable directly with a state of consciousness. This has the empirical consequence that there had better be a distributed quantum condensate (or other locus of entanglement) somewhere in the brain, causally situated so as to function as a Cartesian theater and locus of consciousness. All I'm doing is displacing the hard problem onto the properties and structures of that hypothesized quantum object, but it had to be done because the problem appears to be unsolvable out in the world of disentangled 'individual particles'.

Comment by mitchell_porter2 on Do Scientists Already Know This Stuff? · 2008-05-19T02:01:38.000Z · LW · GW

Are you color-blind, Caledonian? Do you ever use color words? Do you think they refer to nothing more than "neurological associations"? Or is it that they do refer to something of which you are directly aware, but which you have a way of talking around?

When I look out the window right now, I see a blue patch of sky. Am I seeing neurological associations? Am I seeing a mathematical description of neurological associations?

You are free to deny that 'blueness is there', but if that is your only counterargument, I have to think my original argument must have been quite strong.

Comment by mitchell_porter2 on Do Scientists Already Know This Stuff? · 2008-05-19T01:11:31.000Z · LW · GW

Caledonian: What evidence do you offer us that mathematical descriptions cannot produce the properties of which you speak?

First of all, let's be clear regarding what we have to work with. Things are complicated a little by the variety of specific theories and formalisms used in physics, but let's take multi-particle quantum mechanics in the configuration basis as illustrative. The configurations are all of the form 'A particle of species a1 at location x1, and a particle of species a2 at location at x2,...', and so forth. The quantum states consist of associations of complex numbers with such configurations. There is the basic dynamical fact that a quantum state ψ evolves into another state ψ + dψ according to the Schrödinger equation, and (if you're not taking the many-worlds path) Born's postulate that the probability of there actually being particles a1, a2,... at locations x1, x2,... is |ψ|^2.

Then there are various entities and facts that can be obtained from these through abstraction, deduction, and comparison, e.g. 'the number of particles in configuration c' or 'the average number of expected particles in quantum state ψ, as calculated via the Born probabilities' or 'the Hilbert-space inner product of states ψ1 and ψ2'. We could, if necessary, describe a formal combinatorial grammar describing all and only those entities and facts implied by the theory-defining postulates in my first paragraph. It would amount to saying: the entities and relationships directly postulated by the theory exist, and so do those which can be logically or mathematically inferred from those postulates. But speaking informally, all we have to work with are featureless spatial configurations of point particles, superpositions thereof, dynamics of superpositions, and empirical probabilities derived from superpositions.

And what sort of entity or property are we trying to extract from the theory, if we are trying to derive consciousness from physics? It's tiresome to resort repeatedly to the same example, but nonetheless, let's consider color: the variety of hues and shades which we lump together into the natural language categories of red, blue, and so forth. (I put it that way because I do not want to turn this into a discussion of whether those natural language categories are "natural kinds". Focus instead on the numerous instances of color which populate visual experience and which unquestionably exist, regardless of how they get categorized.) On one side we have "quantity and causality", as I put it above - and I'll even throw in spatial geometry and dispositional behavior; on the other side, the colors. How might we go about making the latter out of the former?

There are some things we can do. We can quantify certain things about subjective color; and we can describe certain physical realities which are somehow correlated with color. Thus 450-nm wavelength light "is" a type of blue light. But I submit that it makes no sense to say that when you see a particular shade of blue, you are "seeing a length"; or that blue itself "is a length". That might do as a poetic description of the physics behind the perception, but as an ontological statement, it simply substitutes the correlated geometric property for the sensory property we are trying to explain.

Another approach is the cognitive one: things are blue because your nervous system classified them that way. But although the correlated purely-physical property is a lot more complicated here, it's the same story. Put informally, to use this as an explanation of blueness is to say that our perceptions turn blue because we call them blue or think they are blue.

I think Dennett would understand my point, but as usual he bites the bullet and denies that color is there. He calls it "figment" - figmentary pigment - because according to physics, there is nothing actually blue, inside or outside one's head. But blueness is there, therefore that ontology is wrong.

"Emergence" is a popular dodge: colors and other subjective properties, though not being identical with any elementary physical property, somehow "emerge" when a brain enters the picture. Apart from being vague, that's just dualism: if the emergent properties are not identical with one of the purely physical properties in that combinatorial grammar I mentioned, then it is different from all of them, no matter how correlated it is.

As I said, my answer is to turn it around, and to say that the existence of blueness (etc) is axiomatic, and so it must be one of the things that a true and complete theory of reality would be about. It is as if one were to look at electromagnetism and say, my God, those things we thought were lengths, they're actually colors! - rather than vice versa. But it's also my thesis that when you look at doing this in detail, some of the obvious candidates for this ontological inversion, such as "computational states of neurons", present too many specific difficulties to work (in that case, because a computational state of a meso-scale system like a neuron is a vague property, microphysically speaking). Thus I find myself pursuing quantum ontological exotica.

Comment by mitchell_porter2 on Do Scientists Already Know This Stuff? · 2008-05-18T06:38:12.000Z · LW · GW

Eliezer: From all the books that created me, I was never once warned that Science is not strict enough.

I am trying to figure out exactly what your better methodology is. Is it

(1) Science + Occam's razor, with the razor used to choose between experimentally indistinguishable theories?

(2) Bayes's Law, with Science somehow merely being an application of the law?

(3) Science, Bayes, and an assortment of introspective methods meant to prevent wasting one's time on a-priori extravagant hypotheses?

I do not think anyone will argue with the advice that if a theory contains entities which are predictively irrelevant, you should try doing without them. Whether "Science" is merely an instance of "Bayes" will be a little more contentious; to employ probability theory requires structure - a space of possibilities, a prior on that space - which may not be available. The utility of the psychological tips is even more open to question, though it's surely useful to at least know about this perspective.

Some of the examples you use I have to disagree with. I do not think many worlds can be shown to be the clear favorite among quantum interpretations, either by the simple argument that it's orthodoxy minus collapse and therefore simpler than orthodoxy, nor by some more complicated argument that also tries to incorporate qualitative principles like adherence to the spirit of relativity. You are also getting Penrose wrong, as I wrote above. People adopt quantum mind theories for a variety of reasons. For example, I do it because I do not believe in the reducibility of consciousness to a collective or swarm phenomenon, and some of the quantum ontologies permit options that don't exist in classical atomism. But Penrose did it because it gave him a means of physically implementing neural hypercomputation, which in turn he deemed to be necessary because of the incompleteness theorems. He was not trying to explain qualia, so the fact that his hypothesis introduces no insight on that front is irrelevant.

The most profound criticism I can make of science as it is presently conducted is that it assumes a type of ontology which is necessarily wrong; and this really only applies to sciences which touch on something ontologically fundamental. The ontology assumed might be called objectified mathematical materialism; it is necessarily wrong because conscious experience manifestly contains properties which cannot be obtained by any combination of the entities which that ontology says are all that exists; but this is irrelevant to, say, a biologist, unless their work really does touch upon consciousness. A biologist can utilize the everyday subjective ontology, and the quantitative world-image of the natural sciences founded upon physics, and not have them clash in an impossible way.

Your younger self sensed, correctly, that something more is needed. If he made an error, I would say it was in supposing that more of the same could make a difference: that extra mathematical physics can solve the hard problem. Even if it's there, and causally relevant, it's just more physics. What's needed is new ontology. Realist fundamental physics is ontology, so a change there does mean new ontology, but if it's just mathematics, it's not enough. We have to remember that subjectively speaking, the mathematical image of the world was created by deliberately excluding from consideration certain aspects of experience as "secondary", and that the hard problem of consciousness arises from this unfinished business. I've given my prescription in comments elsewhere: transcendental idealism, transcendental phenomenology, and a quantum monadology in which the qualities revealed in appearance are taken to be the ontological content behind the mathematical formalism used to describe the physical correlates of consciousness.

Even though they are based on the impoverished ontology of mathematical physics, according to which quantity and causality are everything, I do think some of your qualitative methodological principles are still relevant to these deeper investigations. But they would have to be applied in a frame of mind which no longer tries to ground everything in mathematics as we know it, and remains open to aspects of being which fall radically outside anything we know how to formalize at present.

Comment by mitchell_porter2 on Where Physics Meets Experience · 2008-05-17T07:12:28.000Z · LW · GW

A belated meta-response to Caledonian: this is your earlier remark to which I referred. We may have no more than a terminological difference. As I said above, I would (hope to) never say "A exists relative to B", only that A was detectable, rationally inferable, etc., relative to B. It's too confusing to use "existence" as if it only means "epistemically assertible existence".

Comment by mitchell_porter2 on Many Worlds, One Best Guess · 2008-05-17T06:57:57.000Z · LW · GW

Günther, I have previously argued that vagueness is not an option for "mind" and "world", even if it is for "baldness" or "heap of sand" or "table". The existence of some sort of a world, with you in it, and the existence of a mind aware of this, are epistemic fundamentals. Try to go vague on those and you are in effect saying there's some question as to whether anything at all exists, or that that is just a matter of definition. Your mind in your world is the medium of your awareness of everything. You are somewhat free to speculate as to the nature of mind and world, but you are not free to say that there's no fact of the matter at all.

This whole situation exists because of the particular natural-scientific models we have. But rather than treat the nonvagueness of mind and world as an extra datum to be used in theoretical construction, instead we get apologetics for the current models, explaining how we can do without exactness in this regard. It's all rationalization, if you ask me.

Comment by mitchell_porter2 on Do Scientists Already Know This Stuff? · 2008-05-17T05:59:47.000Z · LW · GW

The point is incidental to this essay, but Penrose's idea is not a "mysterious answer to a mysterious question". The question is: How could the human brain do more than a universal Turing machine can? The answer is: By there being an objective wavefunction collapse process which is noncomputable in its dynamics and relevant to cognition. Penrose is not even trying to solve the problem of consciousness, though he flags it as an important issue; his theory is an exercise in the physics of hypercomputation. He is motivated by an interpretation of Gödel's results which most people do not share, but then all you can say is that it is a complicated answer to an irrelevant question.

Comment by mitchell_porter2 on The Dilemma: Science or Bayes? · 2008-05-15T12:18:00.000Z · LW · GW

People who want to get fundamental physics out of cellular automata could be a lot more imaginative than they are. What about small-world networks? Maybe you could get quantum nonlocality. What about networks which are only statistically regular? Maybe you could get rotational symmetry in the continuum limit. And how about trying to do without a universal time coordinate? What about creation and destruction of cells, not just alteration of cell states? Euclidean, gridlike CAs like Fredkin's should only be a training ground for the intuition, not the template for modeling the real world.

With respect to the topic of this article, though I've flamed many-worlds for not really delivering on its promises, cellular-automata physics is not remotely comparable. Even billiard-ball physics is better empirically - at least it can reproduce Newtonian gravity! CAs haven't even done that. You can't say "Occam's razor favors X" if you haven't actually got X to work yet.

Comment by mitchell_porter2 on The Dilemma: Science or Bayes? · 2008-05-14T05:05:00.000Z · LW · GW

This is a stupid analogy, but:

Suppose we have a software package, UnitaryQM, of predefined functions. There is a competition, the Kolmogorov Challenge, in which you have to implement a new function, Born(). There are two development teams, Collapse and MWI. Collapse does the job by handcoding a new primitive function, collapse(), and adding it to the library. The MWI team really wants to use just the existing functions, but MWI 1.0 actally gives the wrong answers. The current hope for MWI 2.0 is a function called mangle(), but mangle only exists as pseudocode. The MWI team know how they want it to behave in certain limits, but to completely specify it requires an arbitrary parameter, objectiveDecoherenceThreshold.

Now interestingly, there have been two generations of Collapse as well. In Collapse 1.0, collapse has to be called directly by the user, from a command line. In Collapse 2.0, collapse can be called from within another function; but of course, now you can't rely on the user to determine when it happens. So instead there is an adjustable parameter, objectiveCollapseFrequency.

The Collapse 2.0 team are at peace with the fact that their implementation of Born requires a free parameter, and they have consequently submitted some actual code to the Kolmogorov Challenge. The MWI 2.0 team are not. As a result, they haven't submitted any code, just pseudocode. Obviously Collapse 2.0 wins by default.

Comment by mitchell_porter2 on The Dilemma: Science or Bayes? · 2008-05-14T04:09:00.000Z · LW · GW

Tom, Nick, MWI does not make predictions! Well, there is a version of MWI that does, but it is not the one being advocated here.

What makes predictions is a calculational procedure, like sum-over-histories. That procedure has an interpretation in a collapse theory: the theory explains why the procedure works. The version of MWI that Eliezer has expounded cannot do that. He has said so himself, repeatedly - that the recuperation of the Born probabilities is a hope, not an existing achievement.

Is that clear? I feel like I had better say it again. The bare minimum that all quantum physicists share is an algorithm for making predictions. An objective collapse theory offers an explanation as to why that algorithm works. It is a theory about what is actually there, and how it actually behaves, from which that algorithm can be derived.

Many worlds is also a theory (or a class of theories) about what is actually there. But when you count the worlds, the numbers come out wrong, badly wrong. So something has to change. Robin Hanson has suggested a different approach to the problem; but as I have objected, it remains vague on the crucial detail of exactly when the transition between one world and many worlds takes place. In any case, this brand of many worlds simply cannot yet offer an exact justification of the predictive algorithm in the way that a collapse theory can. It's not true that MWI and collapse make the same predictions; rather, the hope is that MWI will predict what collapse already predicts, once we understand it properly.

Comment by mitchell_porter2 on The Dilemma: Science or Bayes? · 2008-05-14T00:48:00.000Z · LW · GW

Among all these comments, I see no appreciation of the fact that the version of many worlds we have just been given CANNOT MAKE PREDICTIONS, whereas "collapse theories" DO.

Yes, Schrödinger evolution plus collapse is more complicated than just Schrödinger evolution. But the former makes the predictions, and the latter does not. We have been given the optimistic assertion that maybe the predictions are already somewhere inside the theory without collapse, but this remains to be shown. That's what the meaning of this whole "quest for the Born probabilities" is about! It is, precisely, the quest to restore the predictive capacity of quantum mechanics after you've taken collapse away. And the fact that it's a quest tells you that this is a research program whose goal is not accomplished.

Comment by mitchell_porter2 on The Dilemma: Science or Bayes? · 2008-05-13T10:25:35.000Z · LW · GW

Tim, I thought there was only one "shut up and calculate" interpretation, and that's the one where you shut up and calculate - rather than talking about many worlds. Perhaps you mean it's a "talk rather than calculate" interpretation?

Suppose I announce the Turtles-All-The-Way-Down "interpretation" of quantum mechanics, is it fair to say that the TATWDI "makes the same predictions" if I can't actually show how to get a number or two out of this postulated tower of turtles, but just say it's a way of thinking about QM? If MWI makes predictions, show me how it does it.

Comment by mitchell_porter2 on The Dilemma: Science or Bayes? · 2008-05-13T09:00:23.000Z · LW · GW

Collapse theories can do something many worlds can't do: they can make the predictions! As can Bohmian theories.

Many worlds, like at least one other prominent interpretation (temporal zigzag), is all promise and no performance. Maybe Robin Hanson's idea will make it work? Well, maybe Mark Hadley's idea will make the zigzag work. Hadley's picture is relativistic, too.

Many worlds deserves its place in the gallery of possible explanations of quantum theory, but that is all.

Comment by mitchell_porter2 on Many Worlds, One Best Guess · 2008-05-13T01:28:10.000Z · LW · GW

A further implication of "quantum theory as field theory of configuration space": It means that "spatial configurations" are merely coordinates, labels; and labels are merely conventions. All that really exists in this interpretation are currents in a homogeneous infinite-dimensional space. When such a current passes through a point notionally associated with the existence of a particular brain state, there's no picture of a brain attached anywhere. This means that the currents and their intrinsic relations bear all the explanatory burden formerly borne by spatial configurations in classical physics.

Dustin, what question are you talking about? Question to whom? The only comments I see from you are addressed to Caledonian, in the previous post in this series.

I am afraid that I find the relational interpretation to be gibberish. "The character of each quantum event is only relative to the system involved in the interaction." Can we apply this to Schrödinger's cat? "The cat is only dead relative to its being seen to be dead", perhaps? The cat is dead, alive, neither, or both. It is not "relative".