Comment by mlionson on David Deutsch: A new way to explain explanation · 2010-03-29T00:06:27.976Z · LW · GW

I don't think he is saying, "good explanations are hard to vary while preserving their predictions".

As described above the statement "Everyone just acts in his own interest" very easily preserves its predictive power in a multitude of situations. Indeed, the problem with it is that the statement preserves its predictive power in too many situations! The explanation is consistent with just about whatever happens, so one cannot design a test that makes one believe that the statement is certainly false. So it is too easy to vary and hence a bad explanation.

Comment by mlionson on Against Modal Logics · 2010-02-24T04:27:47.598Z · LW · GW

Evolution does not increase a species' implicit knowledge of the niche by replicating genes. Mutation (evolution's conjectures) creates potential new knowledge of the niche. Selection decreases the "false" implicit conjectures of mutations and previous genetic models of the niche.

So induction does not increase the implicit knowledge of gene sequences.
Trial (mutation) and error (falsification) of implicit theories does. This is the process that the critical rationalist says happens but more efficiently with humans.

Comment by mlionson on Many Worlds, One Best Guess · 2010-02-20T06:31:35.710Z · LW · GW

I think I see where we are disagreeing.

Consider a quantum computer. If the laws of physics say that only our lack of knowledge limits the amount of complexity in a superposition, and the logic of quantum computation suggests that greater complexity of superposition leads to exponentially increased computational capacity for certain types of computation, then it will be quite possible to have a quantum computer sit on a desktop and make more calculations per second than there are atoms in the universe. My quote above from David Deutsch makes that point. Only the limitations of our current knowledge prevent that.

When we have larger quantum computers, children will be programming universes with all the richness and diversity of our own, and no one will be arguing about the reality of the multiverse. If the capacity for superposition is virtually limitless, the exponential possibilities are virtually limitless. But so will be the capacity to measure “counterfactual” states that are more and more evolved, like dead cats with lower body temperatures. Why will the body temperature be lower? Why will the cat in that universe not (usually) be coming back to life?

As you state, because of the laws of thermodynamics. With greater knowledge on our part, the exponential increase in computational capacity of the quantum computer will parallel the exponential increase in our ability to measure states that are decohering from our own and are further evolved, using what you call the “Everett camera”. I say “decohering from” rather than “decoherent from” because there is never a time when these states are completely thermodynamically separated. And the state vector has unitary evolution. We would not expect it to go backwards any more than you would expect to see your own cat at home go from a dead to an alive state.

I am afraid that whether we use an Everett camera or one supplied to us by evolution (our neuropsychological apparatus) we are always interpreting reality through the lens of our theories. Often these theories are useful from an evolutionary perspective but nonetheless misleading. For example, we are likely to perceive that the world is flat, absent logic and experiment. It is equally easy to miss the existence of the multiverse because of the ruse of positivism. “I didn’t see the needle penetrate the skin in your quantum experiment. It didn’t or (even worse!) can't happen.” But of course when we do this experiment with standard needles, we never truly see the needle go in, either.

I have enjoyed this discussion.

Comment by mlionson on Many Worlds, One Best Guess · 2010-02-19T04:37:34.560Z · LW · GW

“To really make progress here, what we need is a thought-experiment in which a macroscopic superposition is made to yield information about more than one branch, as the counterfactualist rhetoric claims. Unfortunately, your needle-in-the-arm experiment is not there yet, because we haven't gone into the exact details of how it's supposed to work. You can't just say, 'If we did a quantum experiment where we could produce data about glucose levels in someone's bloodstream, without the needle having gone into their arm, why, that would prove that the multiverse is real!' Even just as a hypothetical, that's not enough. You need to explain how the decoherence shielding works and what the quantum readout system is”

I think you are mistaken here, Mitchell. But let me first thank you for engaging. Most people, when confronted with different outcomes than they expected from the fully logical implications of their own thinking, run screaming from the room.

Perhaps someone could write on these very pages a detailed quantum mechanical and excellent description of a hypothetical experiment in which a “counterfactual” blood sugar measurement is made. But if so, would that then make you believe in the reality of the multiverse? It shouldn’t, from a logical point of view. Because my (or anyone else’s) ability to do that is completely irrelevant to the argument about the reality of the multiverse...

We are interested in the implications of our understanding of the current laws of physics. When we now talk about which “interpretation” of quantum mechanics is the correct one, and that is what I thought we were talking about, we are talking about interpreting the current laws of physics. (Right?) What do the currently understood laws of physics allow us to do, using whichever interpretation one wants, since each interpretation is supposed to give the same predictions. If all the interpretations say that we can make measurements on counterfactual realities, then do all of the interpretations still make logical sense?

I think I have not yet heard an answer to the question, “Is there a current law of physics that prohibits a blood sugar measuring device from measuring counterfactual blood sugars?

Since I doubt (but could be mistaken) that you are able to point to a current law of physics that says that such a device can’t be created, I will assume that you can’t. That’s OK. I can’t either.

To my knowledge there is no law of physics that says there is an in principle limit on the amount of complexity in a superposition. If there is, show me which one.

Since there is no limit in the current laws of physics about this (and I assume we are agreeing on this point), those who believe in any interpretation of quantum mechanics (that makes these same predictions) should also agree on this point.

So adherents to any of the legitimate quantum mechanical interpretations (e.g Copenhagen, Transactional, Bohm, Everettian) should also agree that our current laws of physics do not limit the amount of complexity in a superposition.

And if a law of physics does not prevent something, then it can be done given enough knowledge. This is the most important point. Do you (Mitchell) dispute this or can anyone point out why I am mistaken about it? I would really like to know.

So if enough knowledge allows us to create any amount of complex superposition, then the laws of physics are telling us that any measurement that we can currently perform using standard techniques (for example measurements of blood sugars, lengths of tables, colors of walls, etc.) can also be performed using counterfactual measurement.

But if we can make the same measurements in one reality as another, given enough knowledge, why do we have the right to say that one reality is real and the other is not?

Comment by mlionson on Many Worlds, One Best Guess · 2010-02-18T06:48:08.523Z · LW · GW

“By modulating the boundary conditions we are exploring logical possibilities, and that is how we probe counterfactual realities (in the transactional interpretation)”

But note then that these “logical possibilities” must render a complete map of the blood and all its atomic and subatomic components and oxygen concentration, because without these components and a heart beating properly to oxygenate the blood, the measurement of the blood sugar would be wrong. But without an atmosphere and a universe that allows an atmosphere to have appropriate oxygen content and lungs to breath in the oxygen, the blood sugar measurement would also be wrong.

But it is not wrong.

So this “logical possibility’ (blood sugar measurement with actual result) must simulate not only the blood, but the heart, the person, the planet on which he resides and the universe which houses the planet, in order for the combined quantum state to appropriately render a universe to calculate the correct results of a blood sugar measurement (or any other wanted measurement) that is made on this merely “possible” universe. Does anyone seriously doubt that multiple different measurements could be made on this so-called merely “possible” universe to make sure that it performs like ours? (Blood sugar measurement, dimensions of room in which experiment was performed, color of wall, etc.)

It is almost humorous to have to ask, “What is the difference between a map that renders every single aspect of a territory, including its subatomic structure, and the territory?”

It is strangely sad (and a tribute to positivism) that we must think that just because we cannot see the needle penetrating the skin, this implies that the blood is merely possible blood, not actual blood. Does our examination of fossils of dinosaurs really imply the mere existence of only possible dinosaurs, just because we can’t see the dinosaurs right now?

So, in order to eliminate the multiverse theory, opponents must believe that blood sugar measurements -- on blood --in people-- on planets-- in a universe--are somehow not real just because you can’t see the needle penetrate the skin. What else is philosophically different from measuring our own blood? Why do we not call our own blood mere possible blood, because when we measure that we also only see the results of the measurement through the lens of our own implicit neuropsychological theories. All data is interpreted through theory, whether it is data about another universe or our own.

Or one must formulate a new law of physics, as Penrose does. Note that one formulates this new law, not because the old laws are not working, but merely because the multiverse conclusion does not seem right to him. I appreciate his honesty in implicitly agreeing that the multiverse conclusion follows unless a new law of physics is invented.

Comment by mlionson on Update Yourself Incrementally · 2010-02-17T09:16:23.842Z · LW · GW

"What makes this theory a good one is that people have eaten turkeys for Thanksgiving in the past and induction tells us they are likely to do so in the future (absent other data that suggests otherwise like a rise in Veganism or something)."

I do appreciate your honesty in making this assumption. Usually inductivists are less candid (but believe exactly as you do, secretly. We call them crypto-inductivists!)

But there is no law of physics, psychology, economics, or philosophy that says that the future must resemble the past. There also is no law of mathematics or logic that says that when a sequence of 100 zeroes in a row are observed, the next one is more likely to be another zero. Indeed there are a literal INFINITE number of hypotheses that are consistent with 100 zero's coming first and then anything else coming next.

With respect, the reason you believe that Thanksgiving will keep coming has everything to do with your a-priori theory about culture and nothing to do with inductivism. You and I probably have rich theories that cultures can be slow to change, that brains may be hard-wired and difficult to change, that memes reinforce each other, etc. That is why we think Thanksgiving will come again. It is your understanding of our culture that allows you to make predictions about Thanksgiving, not the fact that it has happened for! For example, you didn't keep writing the year 19XX, just because most of your life you did so and did so repeatedly. You were not fooled by an imaginary principle of induction when the calendar turned from 1999 to 2000. You did not keep writing 19...something, just because you had written it before. You understood the calendar, just as you understand our culture and have deep theories about it. That is why you make certain predictions (Thankgiving will keep coming but you won't continue to write 19XX, no matter how many times you wrote it in the past.

I think you can see that your rationality,( not a principle of induction, not that everything stays the same) is actually what caused you to have rational expectations to begin with.

Comment by mlionson on Many Worlds, One Best Guess · 2010-02-17T08:50:41.365Z · LW · GW

And if no law of physics precludes something from being done, then only our lack of knowledge prevents it from being done.

So if there are no laws of physics that preclude developing bomb testing and sugar measuring devices, our arguments against this have nothing to do with the laws of physics, but instead have to do with other parameters, like lack of knowledge or cost. So if the laws of physics do not preclude things form happening, we might as well assume that they can happen, in order to learn from the physics of these possible situations.

So for the purposes of understanding what our physics says can happen, it becomes reasonable to posit that devices have been constructed that can test the activity of Elitzur-Vaidman bombs without (usual) detonation or measure blood sugars without needles (usually) penetrating the skin. It is reasonable to posit this because the known laws of physics do not forbid this.

So those who do not believe in the multiverse but still believe in their own rationality do need to answer the question, "Where is the arm from which the blood was drawn?"

Or, individuals denying the possibility of such a measuring device being constructed need to posit a new law of physics that prevents Elitzur-Vaidman bomb testing devices from being constructed and blood sugar measuring devices (that do not penetrate the skin) from being constructed.

If they posit this new law, what is it?

Comment by mlionson on Many Worlds, One Best Guess · 2010-02-17T07:30:04.842Z · LW · GW

The Elitzur-Vaidman bomb testing device is an example of a similar phenomenon. What law of physics precludes the construction of a device that measures blood sugar but with the needle (virtually never) penetrating the skin?

Comment by mlionson on Update Yourself Incrementally · 2010-02-17T07:11:14.622Z · LW · GW

"And if the event happens even more when you expect it to then

it is even more evidence for the theory, "

I am not sure you agreed with this based on your response but I will assume that you did. But correct me if I am wrong!

If you did agree, then consider the Bayesian turkey. Every time he gets fed in November, he concludes that his owner really wants what's best for him and likes him, because he enjoys eating and keeps getting food. Every day more food is provided, exactly as he expects given his theory, so he uses Bayesian statistical inference to increase the confidence he has in his theory about the beneficence of his master. As more food is provided, exactly according to his expectations, he concludes that his theory is becoming more and more likely to be true. Towards the end of November, he considers his theory very true indeed.

You can guess the rest of the story. Turkeys are eaten at Thanksgiving. The turkey was killed.

I think you can see that probabilistic evidence, or any evidence, does not (can not) logically support a theory. It merely corroborates it. One can not infer from an example of something, a general rule. Exactly the opposite is the case. One cannot infer that because food is provided each day, that it will continue to be provided each day. Examples of food being provided do not increase the likelihood that the theory is true. But good theories about the world (people like to eat turkeys on Thanksgiving) helps one develop expected probabilities of events. If the turkey had a good theory, he would rationally expect certain probabilities. For example he would predict that he would be given food up until Nov. 25th, but not after.

I can summarize like this. Outcomes of probabilistic experiments do not tell us what it is rational to believe, any more than the turkey was justified in believing in the beneficence of his owner because he kept getting food in November. Probability does not help us develop rational expectations. Rational expectations, on the other hand, do help us to determine what is probable. When the turkey has a rational theory, he can determine the likelihood that he will or will not be given food on a given day.

Comment by mlionson on Many Worlds, One Best Guess · 2010-02-17T06:30:43.979Z · LW · GW

"True, but many will say it is impossible for all practical purposes."

So the truth of the science is determined by the costs of doing the experiment? By the way, experimentalists are getting far better at creating larger and larger superpositions in making quantum computers, and quantum unitary evolution of the state vector has never been shown to be violated. There is never a time when what could have happened can not effect what does happen.

"The situation resolves into either: 1. The measuring apparatus pierces the skin, has a bloody needle, and reports the result. 2. The measuring apparatus does not pierce the skin, does not have a bloody needle, and does not report the result"

That is just not true according to known laws of physics. The blood sugar measuring apparatus can also be in a superposition of blood being analyzed and blood not being analyzed, along with the superposition of the needle. So the result can in fact be recorded and the experiment can be set up so that the skin is (almost) never penetrated.

Copenhagen people call this type of result a "counterfactual". The fact that something could have happened (the needle going in) changes what does happen (the blood sugar result is measured). Except, the whole counterfactual argument becomes nonsensical when one is talking about blood sugar recordings in needles that never penetrate the skin.

This is precisely the type of situation that David Deutsch writes about when he says the following:

"To predict that future quantum computers, made to a given specification, will work in the ways I have described, one need only solve a few uncontroversial equations. But to explain exactly how they will work, some form of multiple-universe language is unavoidable. Thus quantum computers provide irresistible evidence that the Multiverse is real. One especially convincing argument is provided by quantum algorithms ... which calculate more intermediate results in the course of a single computation than there are atoms in the visible universe. When a quantum computer delivers the output of such a computation, we shall know that those intermediate results must have been computed somewhere, because they were needed to produce the right answer. So I issue this challenge to those who still cling to a single-universe worldview: if the universe we see around us is all there is, where are quantum computations performed? I have yet to receive a plausible reply."

Blood sugar results from needles and measuring devices that were in superposition and results of calculations from qubits in superposition are precisely the outcomes we can expect in the future from utilizing the known laws of physics to our advantage.

Where are the calculations performed? Where is the bloody arm?

Those who do not accept the reality of the multiverse really do have to answer these simple questions, yet invariably they cannot.

Comment by mlionson on Update Yourself Incrementally · 2010-02-17T04:58:24.729Z · LW · GW

"evidence they've gathered adds up to a sufficiently high probability for P"

Perhaps I should ask what you mean by "evidence"? By evidence do you mean examples of an event happening that corroborates a particular theory that someone holds ?

So if

  1. you have an expectation of something happening, and
  2. that something happens,

then you are saying that the event is evidence in favor of the theory. And if the event happens even more when you expect it to then

  1. it is even more evidence for the theory, and this increased probability is calculated by using a Bayesian rule to update your increased expectation of the likelihood of the truth of your theory?

Have I stated your argument correctly?

Comment by mlionson on Update Yourself Incrementally · 2010-02-17T03:02:14.039Z · LW · GW

"For example I don't know how something that is true cannot ever be justified (how else do you know it's true!"

You can't know that something is true. We are fallible. And our best theories are often wrong. We gain knowledge by arguing with each other and trying to point out logical contradictions in our explanations. Experiments can help us to show that competing explanations are wrong (or that ours is!) .

Induction as a scientific methodology has been known (since Hume) to be impossible. Happy to discuss this further if you like. I will certainly read the articles you suggest. Please consider reading David Deutsch's, The Fabric of Realtiy. He (better than Hume in my estimation) shows the 'complete irrationality of induction, but I am happy to discuss, if you are interested.

Comment by mlionson on Many Worlds, One Best Guess · 2010-02-17T02:19:23.803Z · LW · GW

There is no serious quantum physicist who would deny that it is possible to prepare a superposition of states in which a needle penetrates the skin to obtain a blood sugar measurement or does not. This situation could be created, perhaps by briefly freezing a small component of blood and skin on a live person. When this situation predictably resolves into a situation in which the measuring apparatus reads out the result of a blood sugar measurement, though the needle is seen to never penetrate the skin, where was the measurement made?

Where was the bloody needle? Where was the measuring apparatus on which the measurement was made. Where was the arm from which the blood was taken!

Those who do not understand the existence of the multiverse need to provide answers to these simple questions. If the arm is not real in a different universe in which the needle actually went in, how was blood drawn from it and a result reported?

If someone seriously doubts that this scenario can and will be created in the future, which law of physics says that we cannot create this superposition? Which law of physics do you plan to change, to prevent this result, though it has not failed any experiment?

Remarkably, even most of those who deny the existence of the multiverse do not deny that such a blood sugar result could be obtained. This means that virtually all physicists, including those who support Bohm, transactional perspective, Copenhagen, etc., agree that we will be able to obtain a blood sugar result from a needle that never penetrated the arm.

To them I ask again. Where is the arm from which the blood was drawn? Is your hypothesis really that it was drawn in the world of possibility? If so then the map that you call the world of possibility has every component of a real world, including the blood! When the map is as detailed in every respect as the territory, it is the territory. Right?

Comment by mlionson on Update Yourself Incrementally · 2010-02-17T01:10:50.466Z · LW · GW

Although I also think Psi is bogus, my belief has nothing to do with the fact that previous claims of psi have been bogus. Evidence can never justify a theory, any more than finding 10 white swans in a row proves that there are no black swans! Believing that psi is false because of evidence that psi has been false in the past is the logical fallacy of inductivism. Most rational people do not believe in Psi because it has no logical theoretical/scientific basis and because it does not explain things well.

Much of this type of argument strikes me as nonsense. Something that is true can not be justified. One can (and should) argue that something is true. But argument is not justification. If the argument explains something well, then one should believe it, if it is the best theory available.

But evidence can never support any argument. It merely corroborates it. The reason that you believe a coin is fair is not ultimately because the results of an experiment convince you. It would be easy to set up an algorithm that causes the first 3000 examples of a computer simulated coin-flip to have the correct number of heads or tails to make the uninformed believe that the simulated coin flip is fair. But the next 10,000 could yield very different results, just by using an easy-to-create mathematical algorithm. No p-value can be assigned even after 3000 computer simulations of a coin flip. The data never tell a story (to quote someone on another site).

The reason we rationally believe the results of experiment when we flip the coin, but not when we see an apparent computer simulation of a coin flip is: In the case of the actual coin we already have explanations of the effects of gravity on two-sided metal objects, well before we have any data about coin flips. The same is not true about the computer simulation of the coin flip, unless we see the program ahead of time.

It is the theory about the effects of gravity on two-sided metal objects (with a particular pattern of metal distribution) that we try to evaluate when we flip coins. The data never tell us a story about whether the coin is fair. We first have a theory about the coin and its properties and then we utilize the experiment (the coin flip) to try to falsify our notion that the coin is fair if the coin looks balanced. Or, we falsify the notion that the coin is not fair, if our initial theory is that the coin does not look balanced. Examples of a phenomena do not increase the probability of it being true.

The reason we may believe that a coin could be fair is that we first evaluate the structure of the material, note that it seems to have a structure that would promote fairness given standard human flips of coins. Only then do we test it. But it is our rational understanding of the properties of the coin and expectations about the environment which make the coin flip reasonable. The results of any test tell you nothing (logically, nothing at all) about the fairness of a coin unless you first have a theory and an explanation about why the coin should or should not be considered fair.

The reason we do not believe in psi is that it does not explain anything, violates multiple known laws of physics, yet creates no alternative scientific structure that allows us to understand and predict events in our world.

Comment by mlionson on David Deutsch: A new way to explain explanation · 2010-02-16T23:07:17.255Z · LW · GW

He does not mean "lacking unnecessary details". For example the statements "Everyone just acts in his own interest" or "Everyone is really an altruist" are simple and lack unnecessary details, explain quite a lot, and are consistent with Occam's razor. But by Deutsch's criteria they are bad explanation because they are too easy to vary. For example, someone who believes in the self-interest theory could say, "John gave to charity because he would have felt guilty otherwise. So he really was selfish" .

We see that it is easy to change the theory that everyone is selfish to accomodate the case of someone who seems altruistic.

Or someone who believes in the altruist theory could say about John murdering Harry, "Well then, Harry must have been very unhappy."

The altruist theory and the selfishness theory are simple and explanatory in their own way, but too easy to vary. Similarly the idea that that sexism, feminism, capitalism, communism, parental coercion, environmental disregard, etc. cause unhappiness or mental illness or some other broad conclusion are equally meaningless. These explanations are bad because they can be varied to explain ANYTHING.

In contrast, theories that are difficult to vary go out on a limb. They are bold conjectures that explain a lot but even one small counterexample easily invalidates the whole thing. A good theory can not easily be changed to "take into account" the aberration. For example, Einstein's theory of gravitation is a good explanation because it explains a lot, it makes counterintuitive predictions, and even one repeatable counterexample invalidates the whole thing. It can't be easily changed to accommodate something else without invalidating everything else about it.

Theories that are hard to vary remain constant over time. They are more true and therefore more timeless. Invariable theories possess more verisimilitude ("truth-likeness" to use Popper's term).

Like the very best possible theory, truth also cannot be varied. It is completely timeless. It was, is, and always will be true, without any change. That is Deutsch's point.