Jacques Bailhache This exchange between James Higgo and Vic Stenger is interesting, but I don't see the relation with my question : can we chose the proportion of universes in which we decide to act in a certain way ? Or is this proportion determined by the laws of physics ? According to some theories (cf Penrose), the non-determinism of quantum physics may act on our behavior. Some structures in our neurones called microtubules might amplify the non-determinism of the level of a particle to the level of neurons. The behavior of a single particle may act on one neuron and then on our behavior. But the distribution of probabilities of the different possible states of this particle is determined by the laws of physics. So it seems to me that the distribution of probabilities (and then also the proportion of universes) of the different behaviors of the neuron and of the man is also determined by the laws of physics. It seems to me that to have a real possibility of choosing this proportion, there must be another level of choice (for example : choice between [choice between ride with care with probability 0.9 and ride without care with probability 0.1] and [choice between ride with care with probability 0.1 and ride without care with probability 0.9]. To illustrate that : imagine that the world is a tree and you are an ant climbing to it. In the Copenhague interpretation, you can chose to climb to one branch or another. In Many Minds interpretation there are in fact several ants and a given proportion of them climbs to each branch. The choice could still have a signification if it means to chose which ant we are. In MWI, and if suppose that spirit does not exist in duration but only in an instant, we could represent this as if there were some fixed ants all over the tree. In this case the choice does not mean anything. But there could be a possibility of choice if there are several potential trees (with different proportions associated to the branches, or even a different structure of the ramifications) and if we can chose one tree which becomes real. Concerning the exchange between James Higgo and Vic Stenger, the idea of time arrow pointing in different directions is interesting. I wrote a text about this idea.

James Higgo Microtubules are still too large for quantum effects, and they are present in cells other than neurones, so it seems unlikely that their function is to amplify quantum effects. However Stapp has shown that the distances involved in neural synapses are such that there is uncertainty whether a calcium ion released from a neurotransmitter will reach its receptor. In any case, this does not open up scope for non-determinism in the way the word is typically used. In Copenhagen Interpretation, there is a possibility of something choosing what the outcome will be, something initiating a wavefunction collapse. But Copenhagen is plain silly. In MWI everything happens, there is no collapse, so there is no scope for choice. In Stenger's time-reversible interpretation, again, there is no scope for a choice. Penrose is way out on a limb. In the MWI view, we have a 'block universe' made up of every possible universe and time is just a relationship between them. To speak of anything 'happening' - let alone a choice - is meaningless when you take this 'Archimedian' perspective in 'nowhen' (The time issue is mastered by Huw Price in 'Time's Arrow and Archimedes's Point' (1997 I think) - absolutely required reading.). Determinism, free will - all meaningless. In essence, we see a 'law' of thermodynamics simply because we are creatures in time and you could only see us - replicator molecules are only a valid concept - in an 'environment' where entropy increases - the weak anthropic principle. There is NO reason to think that the arrow of time is an objective feature of reality.

James Higgo EVERYTHING is subjective. Nothing is meaningful without an observer choosing to see it by glancing at the block universe from an angle of subjective choosing. Time does not flow. Nothing happens unless someone strings the snapshots together in such a way as they see things happening - we creatures in time can do no other. So it is MEANINGLESS to think of 'choice' or 'determinism'. Two meaningless words can be as compatible as you like.

Gilles Henri I share this point of view. However even if everything is somewhere subjective, there are definitely some things more objective than others. It's easier for me to measure your mass ( and to be in accordance with any observer about it) than your conscious state ; more generally you must explain why the world presents the appearance of a time-evolving one, following definite physical laws. There MUST be some structure behind that (maybe Bruno's number theory, although it is for me questionable). Solipsism for example doesn't give any justification for that.

James Higgo I explain why "the world presents the appearance of a time-evolving one" using the weak anthropic principle: we can only 'exist' in a world which presents the appearance of a time-evolving one. I deny categorically that anything is more objective than anything else. And I use Ockham's razor to slash anyone who disagrees with me.

Russell Standish I think this [James’s] position is closest to mine. I do not see a conflict between free will and determinism. Free will is a phenomenon which is observable in Tegamrk's frog picture. Determinism is only observable in the bird picture. Someone in the bird picture might say that free will is an 'illusion'. To someone in the frog picture, it is entirely real, however determinism is not. There is no conflict here, only two different ways of looking at the world - like looking at light as either a particle or a wave.

Wei Dai Is consciousness based on information or computation? Let me give an example to explain what I mean. Suppose there is a computer running an AI program. Assuming computationalism, this computation should contribute to the measure on conscious experiences. Now suppose there are two computers independently running two identical AI programs with the same inputs. This should make twice as much contribution to the consciousness measure. But now suppose there is one computer running an AI program, and a second computer that makes a copy of the first computer's state after every operation. My question is how much contribution to the consciousness measure does this setup make, compared to the single computer setup? If consciousness is based on computation, then it makes the same contribution, since there is just one instance of the AI computation being run. But if consciousness is based on information, then it makes twice as much contribution, since there are two copies of the AI's state at any given time. So which is it?

Bruno Marchal I am not sure I understand why you choose the words computation and information, but let use these words. Neither don't Ifeel easy with the expression "measure of consciousness" : I understand it as a question of measuring conditionnal probabilities. Let me put it in the following way : You are computationnalist so you are willing to use (classical) teletransportation. So your instantaneous description is read at Amsterdam (let us say) and then you are annihilated (100% of success, this is not possible with MWI, let us suppose it is possible for the sake of the argument). Then you are build following the description at Washington in one exemplar, and you are build in Moscow in 9 exemplars. What is your expectation, when you are at Amsterdam of feeling yourself appearing in Washington after the experiment ? I suppose the 9 exemplars in Moscow are build in identical but separate closed rooms. Would you say there is something like 1/10 of appearing in Washington and 9/10 appearing in Moscow ? For computationalism making sense, I believe there must be a difference. If there is no difference there is a risk of collapsing all computational state, at least from a first person point of view. I think that this question is fundamental both for the computationalist and any many-worlder. Nevertheless it is not easy to formalize such question. I think it is an important open problem.

Gilles Henri I personally deny the concept of "measure of conscious experiment". I deny the fact that consciousness is an *objective* property of matter, just because you can not define a physical property, measurable by an external apparatus, whose measure could determine the degree of consciousness (or if you can, let me know).

Bruno Marchal OK, but just replace "measure of conscious experiment" by "probability of having a personal experience". See above.

Gilles Henri Much of the discussion about consciousness is plagued by this fact, because we include it in formalisms that have not been devised to handle it. The only consciousness we know is our own one, by means that are different from those we use to interact with the outer world. We think that the other human beings are conscious because of the similarity of their behavior with ours, but it does not define what is consciousness. If one succeeds in building a computer with a human-like behaviour (which is quite possible in my sense), deciding if it is actually conscious or not is purely a matter of convenience, not an intrinsic property. In other words, I think the proposition "Another than me is conscious" is really unprovable.

Bruno Marchal That is a very important point. Note that the proposition "I am conscious" is also unprovable. I am used to define quasi-axiomatically consciousness by this very property. To be conscious = to know something and to feel that it is not possible to prove it. This make it possible to find objective root for subjectivity. The existence of unprovable (by a machine x) but true (about machine x) proposition encourage to use logic for the search of objective foundation of subjectivity.

James Higgo So it is MEANINGLESS to think of 'choice' or 'determinism'. Two meaningless words can be as compatible as you like.

Bruno Marchal I think it is a question of level. At the arithmetical level or if you prefer at the level of the wave function of the universe 'choice' has no meaning. But at that level things seems to me to be deterministic (Schroedinger equation is determinist). But at the personal higher order level, choice has a meaning. The meaning is linked to the fact that I am ignorant -for all practical purpose- of the low level, AND I can reflect that practical ignorance and feel obliged to make choice. If not, any lawyer could defend anyone very easily : O member of the jury, please, indulge poor Bill Clinton, after all, all he has done is just obeying physical deterministic equation ! And of course the jury can propose the death penalty to poor Bill, justifying themselves by invoking the same equation. Well, by saying that 'choice' has no meaning, you take the risk of denying the meaning of any high level psychological term, and to produce something like an ethical collapse.

James Higgo wrote also

>In the MWI view, we have a 'block universe' made up of every possible universe and time is just a relationship between them. To speak of anything 'happening' - let alone a choice - is meaningless when you take this 'Archimedian' perspective in 'nowhen' (The time issue is mastered by Huw Price in 'Time's Arrow and Archimedes's Point' (1997 I think) – absolutely required reading.). Determinism, free will - all meaningless.

Bruno Marchal Right, but WE are NOT living at the Archimedian level. We do have free will, just because we cannot determine ourself completely, and we can reflect that. And free-will could be an objective property of any sufficiently rich machines embedded in that 'block universe'.

James Higgo wrote: >There is NO reason to think that the arrow of time is an objective feature of reality.

Bruno Marchal Same remark. I agree with that (as a matter of fact I do think there is no reason to think that any physical stuff has an objective feature in reality). BUT here too, I do think that there could be an objective feature to the existence of the feeling of the arrow of time for a machine (or observer) which can only postulate the existence of the Archimedian level. The intrinsic limitation of the observer can be founded on objective law linking the observer and the Archimedian level. Exactly like Everett when he gives objective reasons (Schroedinger equation) for subjective probabilities (personal histories of automaton).

James Higgo Bruno has clarified nicely what I have been trying to say. There is choice and free will in the environment we inhabit, but it is not an objective feature of reality.

Wei Dai But if everything exists, that would imply every conscious experience has the same measure, which then implies that the set of conscious experiences is finite. The existence of consciousness other than our own has no observable effects, but we believe it on a priori grounds. I think some conscious experiences must have greater measure than others, otherwise we have no explanation for why our own conscious experiences are so simple and regular.

James Higgo How can 'measure' possibly have any meaning in an infinite universe. What is 50% of infinity? Exactly.

Hal Finney I still don't see how the Anthropic Principle forbids universes with a mixture of forwards- and backwards-time regions. As long as we evolve in a forwards-time area we should be protected from backwards-time effects. But once we look out into new regions we should expect to see some where time is running backwards, if all that prevented it was the AP.

James Higgo WAP does not forbid anything, except things which would not allow us to exist.

Hal Finney I see identity in a larger sense. Consider the example proposed by Jacques, where the universe is infinitely large, and there are an infinite number of exact, perfect, indistinguishable copies of me spread throughout the universe. (Each of those copies exists within a region of space, billions of light years across, which is observationally indistinguishable from our own.)

Gilles HENRI I dislike this analogy. If there exist some part of the Universe "perfectly indistinguishable" from another one, it means that this part has the same surrounding, and by continuity that the Universe is in fact periodic, each part having the same copy at the same distance. It is equivalent to say that the topology of the Universe is closed (torus-like), and you can assimilate it to a finite one.

Hal Finney No, it doesn't mean this. We see only a finite-sized bubble of space. If the universe is infinite, there are an infinite number of such bubbles, each spatially separated from the others. Among this infinite number of bubbles will be all physically possible arrangements of matter, with each arrangment occuring an infinite number of times. In particular, the arrangement of matter we see around us will also be repeated an infinite number of times, as well as all variations on it. This can be true only during a finite time for two given regions. If two bubbles are identical up to some distance R, the differences in their surroundings will produce different electromagnetic and gravitational perturbations that will propagate to the centre in a time R/c. So while it is true that at a given time they are an infinite number of identical regions, it also true that this identity must cease for all pairs after a given time. It is not justified to assimilate as identical two parts (or beings) that share only temporarily the same history. Furthermore an infinite deterministic universe is not equivalent to MWI. If there are exact copies of yourself, they must by definition follow the same history, so you cannot consider different evolutions of yourself. If evolutions are different, it means that they are not copies of yourself. This is not periodicity, it is merely the repetition of a finite sequence within an infinite sequence, like finding the string "141" an infinite number of times among the digits of pi. The equivalent is that the density of identical sequences decreases with their length. How about if we have the computers also simulate an environment for the intelligence to interact with. There can be a whole simulated world, with other organisms, complex environments, dramatic variations in conditions, etc. The simulated world can be as complex and intricate as we desire. Can't intelligence exist in such a world?I doubt that it is conceivable to simulate a whole Universe WITHIN this Universe. The only logical possibility would be that we are ACTUALLY the product of a computation in a larger, meta-Universe with computers much larger than our own universe (But how were they built?). Of course you can conceive simplest versions of a Universe with simpler organisms. This is actually realized in any computation. The problem again is that we call consciousness a property that MUST have (by definition) about the same complexity as our own behavior, and we are adapted to the complexity of our world, not of a simpler simulation (you can of course extend the definition of intelligence to much simpler behaviors, but it won't help to understand us!) So for me an intelligent computer (in our world) must NOT include the simulation of its own environment, to be considered as intelligent (the brain itself does not !). It must be adapted to the external world, which means also that two different intelligent computers must be considered as different.

James Higgo Gilles, I agree strongly that 'consciousness is not an objective property.... but a functionality' but you do not need i/os -interfaces with some external reality - because other mental objects can act on yet other mental objects. Buddhist thinking about consciousness is helpful here, as is Liebnitz.

Gilles Henri Well, I have more sympathy for budhism than for other religions, but I do not take it without discussion! I don't know what is a mental object without i/os. I don't know how to think of something that I cannot relate to some perception in any way. For me consciousness IS the capability of reactivating perceptions that we have had from our interaction with the outer world, or our own body. "Mental creation" is only a rearrangement or an extrapolation of these known sensations.

Hal Finney It seems that there are two ways to increase the measure of copies and near-copies of yourself which have favorable experiences. [...] The other method is by killing yourself when things go wrong. [...] By doing so they are increasing the fraction of their near-copies which have good experiences.

Jacques Mallah Like your fellow death-worshipers on this list, you have a very mixed-up understanding of measure. So once again I will take you guys to school. The class is RM 102 - Remedial Measure Theory.

RM102 Syllabus:

1. Historical background

2. Effective probabilities

3. Actual or 'unnormalized' measure

4. The infinite universe model

5. Application to quantum suicide

6. Final Exam

1. The term comes from the mathematical theory of measures, of which probability theory is a subset. A probability is treated as a measure on a set of events with the additional properties that the sum of the probabilities is 1 and that they are nonnegative. The first use of the term 'measure' in the sense of this class, related to effective probabilities, was in the 1957 thesis of Everett. This simple concept is a prerequisite for understanding the basic concepts of the MWI.

2. An effective probability is just what it sounds like, and replaces the stochastic concept of probability found in single-world interpretations. A typical observer should expect his observations to be as though they were drawn from a probability distribution of observations equal to the effective probability distribution. By definition, the effective probability of an observation is proportional to its measure. Effective probability is fractional measure, normalized so that the sum is 1.

Actual or 'unnormalized' measure is the actual amount of an certain observation present in a model. Only measure ratios affect effective probabilities, but actual measure is also important. In a computationalist interpretation, actual measure of a computation is equal to the number of implementations of a computation. By definition, if two people agree on the measure distribution for a model, they agree both on all predictions (given by the effective probabilities) and on how much consciousness is present in that model.

An infinite universe with a single-world interpretation is a useful model, because it is easy to follow what is happening, and because by (3.) only the measure distribution of a model is relevant to any analysis of behavior relating to consciousness.

5. When an individual U chooses to commit suicide at time t, assume he has an effective chance p of succeeding, as measured by an external observer. As usual, assume that the measure of an observation is proportional to the number of observers in that branch of the wavefunction, times the squared amplitude of that branch. What are the effects of the suicide, as opposed to what would happen if U never attempted it? The effective probability of an observation being one of those associated with U is decreased. The conditional effective probability, given an observation associated with U, that it is after time t is decreased. The total measure in the universe is decreased, and all of the decrease is in the total measure of U's observations. In sum, it is a costly act for U.

6. Final Exam. Are the circumstances under which it is a good idea to commit suicide the same in the MWI as they would be in a single world interpretation? (Hint: you can use the infinite universe, single world model for the MWI.)

James Higgo Jacques Mallah, we don't care about our measure, we only care if we should buy a tontine in the knowledge that we will benefit from it in 100, 1000, 10'1000 years. We know that in some branches we will, but we don't know if we will experience a smooth flow of consciousness which will inevitably mean we awake one morning to find ourselves 1000 years old. Obviously we don't intend to try to commit suicide (at least until this issue is resolved).

Jacques Mallah I see. You think that if you are killed, your consciousness would magically jump into the other parts of the universe where you-like beings continue to exist. That's what your 'smooth flow of consciousness" amounts to. Well, if that were true, then the amount of 'you' in the universe would not really decrease. Your measure would by definition be conserved as a function of time, but would become more concentrated in the survivors. But of course there is absolutely no reason to think that; it's nothing more than your version of religion. Logic says that since copies are independent, your measure would be proportional to the number of surving copies and would decrease. The fact that you are still saying you don't care about measure, indicates to me that you still don't understand the concept. Perhaps Darwin has more work to do.

James Higgo Jacques, Darwin has a lot of work to do before I become a slave to my genes, which is what you advocate. I don't say consciousness jumps magically. Our consciousness, like anything, exists in the same form in very many sets of universes. It doesn't make sense to say 'I am that one' or 'no, I'm that one'. You are all of them, and as many sets you could call 'you' get 'shut down' because of a vacuum collapse or supernova or quantum suicide experiment, they become no longer you, and irrelevant to you. This is not an everyday concept, and I am not surprised you have difficulty with it. But please persevere. Like Bryce DeWitt and MWI, you will eventually be its most ardent champion.

Wei Dai Some future versions of Jacques will become QS champions, and some won't. And if we don't hear from you again, we'll assume that you rigged your computer to explode upon receiving an unfavorable reply from Jacques... Seriously, why can't we agree that there is no single right answer here, just like there is no single right answer for the Coke vs Pepsi question. Whether or not QS is rational depends on one's subjective values.