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Jayakar Joseph: on 11/2/13 at 17:14pm UTC, wrote Congratulations, dear Leifer. I think constrains on generalising the...

Héctor Gianni: on 8/10/13 at 22:18pm UTC, wrote Dear Matthew Saul Leifer: I am an old physician and I don’t know nothing...

Howard Barnum: on 8/8/13 at 23:11pm UTC, wrote Matt, I'd love to see your derivation of probabilities in an Everett-style...

Matthew Leifer: on 8/8/13 at 13:09pm UTC, wrote "I'm not sure I'd agree that quantum theory represents a situation in which...

Paul Borrill: on 8/8/13 at 3:16am UTC, wrote Matthew - yours was the last of the over 180 essays I reviewed. I apologize...

Paul Borrill: on 8/8/13 at 0:18am UTC, wrote Dear Matthew - My goal was to review and rate every single essay on this...

Howard Barnum: on 8/7/13 at 23:11pm UTC, wrote Really excellent essay, Matthew, one of the very best here. I'm not sure...

Stephen Anastasi: on 8/6/13 at 12:32pm UTC, wrote Hello Matthew I found your discussion of Bayesianism quite fascinating....


Thomas Ray: "Put another way, Einstein (an expert violinist) allowed that a symphony can..." in Wandering Towards a Goal:...

Joe Fisher: "Dear Eugene Lim and Richard Easther, “Undaunted by the lack of tools to..." in Our Place in the...

agaric backlink: "Obat Liver Paling Ampuh Cara Mengobati Bronkitis Paling Ampuh Cara..." in FQXi Essay Contest 2016:...

anil sharma: "Sometimes it is not possible to take care of infant babies especially while..." in FQXi Essay Contest 2016:...

Amanda Spencer: "hi there" in Quantum Replicants:...

Amanda Spencer: "hi there Hi there nice article." in Quantum Replicants:...

Thomas Ray: "The crux is that the reality of an individual consciousness is far greater..." in Wandering Towards a Goal:...

Marshall Barnes, R&D Eng: "Farzad: Thanks for that helpful breakout of the documentary..." in The Multiverse - Part 2...

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Our Place in the Multiverse
Calculating the odds that intelligent observers arise in parallel universes—and working out what they might see.

Sounding the Drums to Listen for Gravity’s Effect on Quantum Phenomena
A bench-top experiment could test the notion that gravity breaks delicate quantum superpositions.

Watching the Observers
Accounting for quantum fuzziness could help us measure space and time—and the cosmos—more accurately.

Bohemian Reality: Searching for a Quantum Connection to Consciousness
Is there are sweet spot where artificial intelligence systems could have the maximum amount of consciousness while retaining powerful quantum properties?

Quantum Replicants: Should future androids dream of quantum sheep?
To build the ultimate artificial mimics of real life systems, we may need to use quantum memory.

September 23, 2017

CATEGORY: It From Bit or Bit From It? Essay Contest (2013) [back]
TOPIC: "It from bit" and the quantum probability rule by Matthew Saul Leifer [refresh]
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Author Matthew Saul Leifer wrote on Jun. 21, 2013 @ 16:05 GMT
Essay Abstract

I argue that, on the subjective Bayesian interpretation of probability, "it from bit" requires a generalization of probability theory. This does not get us all the way to the quantum probability rule because an extra constraint, known as noncontextuality, is required. I outline the prospects for a derivation of noncontextuality within this approach and argue that it requires a realist approach to physics, or "bit from it". I then explain why this does not conflict with "it from bit".

Author Bio

Matthew Leifer is currently an independent scientist living in London, UK. He completed his Ph.D. in quantum information at the University of Bristol in 2003. He has since held postdoctoral positions at the Perimeter Institute for Theoretical Physics, the University of Cambridge, the University of Waterloo and University College London. His research interests encompass the foundations of quantum theory, quantum information, and the intersection of the two.

Download Essay PDF File

Jochen Szangolies wrote on Jun. 22, 2013 @ 16:38 GMT
Dear Matt Leifer,

very happy to see you entering this contest, and I think your essay touches on a number of interesting themes that seem to be, judging by other essays and some current publications, somewhat 'in the air' at the moment. I've encountered a bit of a language difficulty, however: you use the term 'noncontextuality' in a somewhat different way than I am familiar with---I know...

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Author Matthew Saul Leifer replied on Jun. 22, 2013 @ 17:04 GMT
Hi Jochen,

Thanks for your comments. You are right of course that there are two kinds of noncontextuality: of probability assignments and of value assignments. Quantum theory has the former but not the latter. I think the reason why people do not talk about the former so much is that in operational approaches to quantum theory one simply defines equivalent measurements and preparations to be those that always receive the same probability, so noncontextuality of probability assignments is true by definition. This doesn't work if you are a subjective Bayesian as you can't just posit specific probabilities as a primitive concept in a physical theory.

I am aware of partial Boolean algebras and Kochen's work, as well as a whole bunch of other quantum logical derivations. It seems to me that you can either view these in a realist way as representing the true logic of the world, or as operational logics expressing connections between different experiments we can perform. I argued that Kochen-Specker presents a problem for the subjective Bayesian in the realist approach. The operational approach is more acceptable, but then I think one needs a physical explanation of why we have these structures in terms of what is going on at the ontological level.

Joe Fisher wrote on Jun. 22, 2013 @ 18:37 GMT
Doctor Leifer,

I found your extremely well written essay utterly fascinating to read.

As a decrepit old realist may I make one comment about probability? I contend in my essay BITTERS that only unique exists. There is no way a probable universe could ever come into existence. Only a real unique Universe eternally occurring once is inevitable.

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Author Matthew Saul Leifer replied on Jun. 22, 2013 @ 21:14 GMT
I don't know what you mean by "only unique exists" but I'll have a look at your essay.

Author Matthew Saul Leifer replied on Jun. 22, 2013 @ 22:22 GMT
I looked at your essay. May I remind you that, on the subjective Bayesian view, probabilities only represent your degrees of belief in an uncertain event and do not require the existence of an ensemble of similar experiments. As such, they are perfectly applicable to unique events that only happen once. I am also a realist, as indicated towards the end of my essay, so I don't think we have any real disagreement on these points.

Where I do disagree is that I don't think that uniqueness is a useful scientific postulate. Science is about uncovering patterns is nature and so it necessarily has to look for commonalities rather than singular facts. I admit there may be some truths that are not discoverable by science, and uniqueness of the universe could be such a truth, but I don't see how we could base physics on that.

Hoang cao Hai wrote on Jun. 22, 2013 @ 20:41 GMT
Dear Matthew

You are very good in arguments but lacks a definitive conclusions.

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Author Matthew Saul Leifer replied on Jun. 22, 2013 @ 21:24 GMT
The lack of definitive conclusion is deliberate. All too often people take a very strong stance on the interpretation of quantum theory and see their job as defending their view against all comers. I don't think we will solve any problems this way as it leads to closed mindedness and endless debates where people are talking at cross purposes. Instead, I think the only honest thing to do is to admit that we don't have all the answers and to try and rigorously narrow down the possibilities by converting seemingly philosophical questions into concrete mathematical ones. John Bell showed us how to do this and it puzzles me that so few people follow his lead. Maybe I am more conservative and less stridently speculative than some other essay writers, but I view that as a good thing. We are trying to do science after all and the existing evidence does not lead to clean and immediate answers.

Member Alexei Grinbaum wrote on Jun. 23, 2013 @ 13:26 GMT
Hi Matt,

Thanks for refreshing the memories of my Bayesian years :) Two questions:

1) When you write, "A universe that obeys 'it from bit' is a universe in which not all conceivable decision scenarios are possible", do you imply a universe with quantum mechanics? Or a universe with operational theories (like David Wallace recently described in 1306.4907)? What's your notion of "possible" in this phrase?

2) How about the old question of dimension? Do you take dimension to be a subjective Bayesian thing in the light of new work on dimension witnesses? Or is it objective in some way?



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Author Matthew Saul Leifer replied on Jun. 23, 2013 @ 18:05 GMT
Hi Alexei,

1) In the Dutch book context, a decision scenario consists of a system of bets and it is a "possible" scenario if it is possible to resolve all the bets in the system together. So, for example, a bet that the position of a particle is in a certain range combined with a bet that its momentum is in a certain range is possible in classical physics, but not in quantum theory because...

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Manuel S Morales wrote on Jun. 24, 2013 @ 03:05 GMT

I found your essay to be an excellent analysis of the various aspects of probability in order better understand statistical laws. When you mentioned that probability theory needs to be generalized, I noticed that you did not mentioned how these probabilities can be distinguished as such without defining aspects of certainty. Perhaps I missed that point. Nonetheless, I found your presentation masterfully done and have rated it accordingly. Good luck with your entry.

Meanwhile, I hope you take the time to review my essay which touched upon some of the topics in your essay as well. The findings as presented in my essay have led me to how causality unifies gravity with the strong, weak, and electromagnetic forces as one super-deterministc force, see:

Best wishes,


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Author Matthew Saul Leifer replied on Jun. 24, 2013 @ 12:01 GMT
Thanks. I will take a look at your essay. Unfortunately, I do not really understand the meaning of:

"I noticed that you did not mentioned how these probabilities can be distinguished as such without defining aspects of certainty"

There is probably something being lost in translation here, but what exactly do you want me to distinguish probabilities from and what do you mean by "aspects of certainty". If you can try to clarify then I will do my best to address your concerns.

Jacek Safuta wrote on Jun. 24, 2013 @ 16:50 GMT
Hi Matthew,

Your essay is too difficult for my lack of expertise in that field to discuss technical details at the moment. But it is one of the advantages of the contest we can spot something interesting to learn. Nevertheless I would like to address some general, and in my subjective opinion, important issues.

Jochen Szangolies complains on “troll votes” but we know that the...

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Author Matthew Saul Leifer replied on Jun. 24, 2013 @ 17:18 GMT
Regarding "troll votes" I am inclined to believe that the opinions of the judging panel hold a lot more weight than the community ratings, so I am not too worried about it. Also, troll voters probably give everybody's essays low ratings, so they probably all cancel out in the end.

As for different senses of "it", I do think that physicists share a common language, which is the language of...

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Jacek Safuta replied on Jun. 24, 2013 @ 18:54 GMT
Matthew ,

You are right, the opinions of the judging panel hold a lot more weight however it regards only to finalists. Never mind. A perfect system does not exist.

For you and me it is clear from Wheeler writings that it was not intended to mean "everything is discrete" or "everything is made of information", but rather "everything that appears to us to be real is a result of our interventions into nature" but I have read all the essays in the contest and I can assure you that we are in minority.

The language of mathematics and empirical observation is really a beautiful common language. E.g. the mathematical formulations of quantum mechanics gives a rigorous description nevertheless we have got so many interpretations…

Thanks for the clarifications.


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Akinbo Ojo wrote on Jun. 28, 2013 @ 09:24 GMT
Dear Matthew,

Very nice essay with a lot of reductio ad absurdum type arguments. As a realist myself, let me play Wheeler's game of twenty questions with you...

My chosen word is "non-existence".

It is clear that if you start with questions such as, "Is it a living object?" No."Is it here on earth?" No."Is it red?" No. "Is it round"? No, etc. You will never get the answer, 'Yes' and you must fail.

That being the case, I suspect that the first question, the question at "the very bottom" (Wheeler), that which "lies at the ontological basement" (Paul Davies), that which must first be asked and to which we must first get a No or Yes answer depicted by the binary digits 0 and 1, will be: is it existing (1) or not-existing 0)? It is after you get the answer depicted 1, that you then continue. Hope

I explore the meaning of that first question and its digital answers (Yes/No), here. Agreeing with Julian Barbour that the 0 and 1 cannot be abstract symbols but must stand for something ontologically concrete.

But you redeem the situation somewhat in your conclusion, "We have arrived at the conclusion that noncontextuality must be derived in terms of an analysis of the things that objectively exist. This implies a realist view of physics..."

Best regards,


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Author Matthew Saul Leifer replied on Jun. 28, 2013 @ 17:23 GMT
``It is clear that if you start with questions such as, "Is it a living object?" No."Is it here on earth?" No."Is it red?" No. "Is it round"? No, etc. You will never get the answer, 'Yes' and you must fail.''


To clarify my position, I want to make it clear that I am also a realist, as you can tell from the last section and conclusion of my essay. I am just trying to argue for this in a different style --- one that I hope is more effective against anti-realists. One can develop all sorts of a priori arguments against "it from bit" based on the idea that we should be realists. However, if you are an anti-realist then your response to this would be "What do I care? I am an anti-realist so I do not buy these arguments". To argue effectively against this, one has to start from a position that an anti-realist can support and then argue for realism on those grounds. Now, "it from bit" was posited by Wheeler as a foundational principle within a broadly ant-realist or neo-Copenhagen framework. If we can show that this principle cannot do the work required of it without being backed up with a realist conception of physics, then that should be a much more compelling argument for an ant-realist than any a priori argument for realism. That is the sort of argument I was trying to construct.

George Kirakosyan wrote on Jul. 1, 2013 @ 05:10 GMT
Dear Matthew,

I welcome your essay not for only it written professionally, but there I find very important for my point - the right physical science can not be builded without of realism. I am hopefully by listening this from professionals (it is true, they are not too much at present, or they afraid talk openly!) Let us we connect your realism with your colleague Ben Dribus' demand - to return to a causality principle, taking care also Lee Smolin's conclusion - about necessity to find more weighty interpretation to QM phenomena, then we will come to one complex approach - how to reconstruct physics. I hope you will find some useful things on this matter in my essay, then we can continue talk if you see it reasonable. I appreciate your work on (9)




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Member Giacomo Mauro D\'Ariano wrote on Jul. 1, 2013 @ 22:25 GMT
Dear Matthew,

I enjoyed the first part of your essay, but I couldn’t follow the second part, where you use a language that is unusual for me, despite I have my own baggage of philosophy of probability. As you know I am a Bayesian, but my way of thinking seems to differ from yours more than from that of a frequentist. I really cannot capture your meaning of "context".

For me things...

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Author Matthew Saul Leifer replied on Jul. 1, 2013 @ 23:43 GMT
Hi Mauro,

I am flattered that you think I have philosophical training. I don't. I just read a lot of books about the philosophy of probability.

If you are a follower of Cox then it is definitely true that there is a wide gap between your position and mine. I am a subjective Bayesian in the vein of Ramsey, de Finetti, Savage, Jeffrey et. al. and I think that Cox's derivation of...

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Member Giacomo Mauro D\'Ariano replied on Jul. 2, 2013 @ 09:27 GMT
Dear Matthew

I need to re-read your answer more closely, though there are many point that will remain missing. We would need a real conversation in person. I hope we will someday be able to come back to the old days of our first Cambridge meeting.

The only thing I want to stress here, where it seems that I may have been misunderstood, is that also for me the context is a "parameter" for which it makes no sense to provide a probability. Second simple thing is that I remain convinced that all your line of research is motivated by the realist's epistemic interpretation of probability. Even though I admit that we cannot live without a personal interpretation, I try to stay over interpretations, and look for just the minimization of the axioms, and seeking clear relations between different axiomatizations and theories: things that have a much more general value than pursuing just a single viewpoint. Instead of marking the differences between us, as a rule we should try to understand the relations and the common points.

It is always a pleasure to discuss with you.

My best regards


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Michel Planat wrote on Jul. 2, 2013 @ 08:15 GMT
Dear Matt,

In view of your deep knowledge of what (non-)contextuality means in the different approaches of quantum theory, you may be interested in mine, that is quite orthodox (in the Bohr sense) but pushes the meaning of observables towards graphs, finite geometries and algebraic curves (you would call them epistemic concepts).

Going to your essay, and the related publications, I realize how deep the problem is and I certainly learn a lot by reading you.

Best wishes.


ps/ I completely agree with Jochen Szangolies about the poll-votes.

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George Kirakosyan wrote on Jul. 3, 2013 @ 11:21 GMT
Dear Matthew,

I see you are too busy with interesting discussions.

For this, I just asking you to check my essay in your good time (from above my post) and in two words only write your opinion (it will valuable for me as from professional scientist.) Let me say - there are no any quantitatively reasoning contain, and it will necessary spent short time only to study it.

With best wishes,


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Author Matthew Saul Leifer replied on Jul. 3, 2013 @ 15:48 GMT
Dear George,

There are a lot of interesting essays to read and unfortunately I do not have time to read all of them. I hope you will understand that I cannot guarantee to read someone's essay just because they mention it here. If the abstract looks interesting to me then I will read it and rate it.

This thread is supposed to be for comments about my essay, so if you have something specific to say about it then I would be glad to respond.

George Kirakosyan replied on Jul. 3, 2013 @ 18:11 GMT
Dear Matthew! let me see that my previous post concerns to your work manly (1 Jul, see above.) I did not get response even as small thanks, that may be enough for me. Of course, for us own work is important first that is clear for everyone.



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James Lee Hoover wrote on Jul. 3, 2013 @ 18:01 GMT

If given the time and the wits to evaluate over 120 more entries, I have a month to try. My seemingly whimsical title, “It’s good to be the king,” is serious about our subject.


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Edwin Eugene Klingman wrote on Jul. 4, 2013 @ 21:54 GMT
Dear Matt,

I've read your essay and many of your comments. I particularly appreciate your sober approach: "All too often people take a very strong stance on the interpretation of quantum theory and see their job as defending their view against all comers."

As part of writing my essay, I studied ET Jaynes "Probability Theory: the Logic of Science". Your "Dutch book" discussion is a...

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Author Matthew Saul Leifer replied on Jul. 4, 2013 @ 23:14 GMT
Regarding Jaynes, I made some less than sympathetic comments about the Cox approach to probability in my response to D'Ariano and of course Jaynes relies on that approach as his foundation. As with Cox, I find Jaynes a little too simple minded for my taste, as he ducks some major issues with the choice of prior and makes too many arguments based on simplicity. Of course, Jaynes was working in a...

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Edwin Eugene Klingman replied on Jul. 5, 2013 @ 01:40 GMT
Dear Matt,

Thanks for the answers and explanations. I'm not familiar with Cox, so did not make the connection. Nor am I deeply focused on probability, but instead on the underlying ontology. I may return with a comment or question on the partition function as the basis for a Born interpretation of the wave function, after digesting your answer. You say, "If you want to come up with a fullblown interpretation of quantum theory then I think you need to start from a well-defined ontology. You need to say what things would exist in reality if quantum theory were literally true." I do this, and use the partition function to explain why the wave function yields probability. I guess you would call this a suggestive argument, but it works, and you seem to be happy with that as a start.

You say, "Once we have done that, we then realize that the only thing that matters about the hidden variables for the purposes of the argument is what measurement results they predict." The measurement results predicted by my model yield the cosine result Bell said is impossible -- as long as Alice and Bob make independent choices!

I would hate to steer you away from Gordon's essay because I misstated or badly summarized it. I understand "had your fill", so I won't push the issue, but hope you change your mind.

Your remarks about Ken's approach surprise me. Perhaps I should re-read your exchange with him.

I'm not sure whether you answered the question as to whether non-locality would be obvious had Bell never invented his inequality. If you'd care to clarify it, I'm still interested.

Thanks again for your detailed answers to my questions.

Best wishes,

Edwin Eugene Klingman

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Author Matthew Saul Leifer replied on Jul. 5, 2013 @ 12:39 GMT
"Your remarks about Ken's approach surprise me. Perhaps I should re-read your exchange with him."

Well, I am critical not because I believe that his models are a bad idea, but because I believe that the conceptual framework needs to be developed more carefully. After all, there are ways of writing down classical theories that make them look like they involve weird causality, such as the...

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Peter Jackson wrote on Jul. 5, 2013 @ 20:09 GMT
Dear Matt,

Well argued and mostly very agreeable. I appreciate your views of Bayesianism, Sample Space, psi, probablism and the Born rule, all of which I too discuss. I found your noncontextuality definition fascinating and analogous to a unique new realist derivation of QM. I present this by invoking 'IQbit's, which using orbital angular momentum in 3D space +t can contain more than O(2^n)...

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Edwin Eugene Klingman replied on Jul. 5, 2013 @ 20:35 GMT

I wrote this on your blog [Jun. 9, 2013 @ 22:45]: "As for Bell's so-called 'proof' that no locally real model can produce the cosine squared result, I produce it in my previous essay (link above). Joy has complained that it only works when Alice and Bob make independent selections, but I believe that is implied by Bell's formulation. I'm communicating with MJW Hall who specializes in determining the limiting cases implied by Bell assumptions. So I need to study your EPR discussion more before I form an opinion about it, although I am favorably disposed to your argument that there is a mismatch between statistics and 'real physical interactions' at each detector. I plan to study your approach further."

Thus I agree that the cosine curve can be reproduced, contrary to Bell, but I am not yet committed to the Malus' Law derivation. I still need to study it.

Sorry to intrude on Matt's blog, but he is clearly a stickler for details, so I wanted to clear up that detail.

Edwin Eugene Klingman

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Author Matthew Saul Leifer replied on Jul. 5, 2013 @ 21:39 GMT
This discussion thread is supposed to be about my essay. I am happy for people to talk about their own essays provided this is done in the context of commenting on something specific that I have said in my essay, or something specific that has come up in the subsequent discussion. If you want to make a comparison between something you have said in your essay and something I said in mine then that is perfectly fine, especially if you do so in order to raise a specific question that we can then go on to discuss.

Posts that are essentially just a summary of your own essay and/or a request for me to read your essay are against the FQXi terms of use which state that posts should not be outside the scope of the forum topic.

I do not mean to offend anyone. It is obviously a judgement call as to whether or not a particular post contains substantive comment on my essay and the subsequent discussion, but I will report posts that seem inappropriate to me. It is then up to FQXi to decide whether or not they are appropriate.

Finally, let me reiterate that I cannot read all the essays but I will read those that I think look interesting. I will do this primarily based on reading the abstracts of the essays. Posting a summary of your essay here will not make me more likely to read it.

Akinbo Ojo wrote on Jul. 8, 2013 @ 11:06 GMT
Dear Matt,

I want to be clear and to be able to quote you on this, as I am not sure you gave a committal answer above:

Question: Is existence/non-existence on the list of possible binary choices? That is, 'is IT existing or not existing' among the questions that can be asked in the game of twenty questions?



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Author Matthew Saul Leifer replied on Jul. 8, 2013 @ 11:20 GMT
Within the context of the essay, there are two possible positions that make sense to me. One could be completely operational about things and say that the only things that exist are the readings on our experimental apparatus, e.g. detector clicks, instrument readings and so forth. In that case, we are assuming that our macroscopic apparatus exist, but not that there is necessarily any deeper reality underlying them. However, the position that I prefer is to assume that there are things called quantum systems that exist independently of us and we are just asking questions about the properties of those systems. In that sense, I am assuming that "it" in the sense of "a quantum system" exists and is not being questioned.

Of course, one can also consider situations in which you are not sure whether a particular quantum system exists, e.g. a laser typically emits a superposition of different numbers of photons. In that case, it sometimes makes sense to include a question about whether the system exists if you can ask it without destroying the system. For example, there are heralded single photon sources that produce two photons in an entangled state and then one can use a measurement on the first photon as evidence that the second photon exists.

I hope that answers your question, but of course it depends on precisely what you mean by IT.

Armin Nikkhah Shirazi wrote on Jul. 14, 2013 @ 21:33 GMT
Dear Matthew,

You have presented a very thoughtful and at times surprisingly subtle analysis of the argument that even a subjective Bayesian view of quantum mechanics must be grounded in some sort of external reality, although this reality need not be understood in terms of classical concepts.

It seems to me that your argument could provide a starting point through which quantum Bayesianism could attain wider acceptance. As far as I can tell, a major point of criticism is that QBism does not really offer a clear ontology (if any at all), and I imagine most physicists do not see themselves in the business of figuring out degrees of belief. Your approach reminds me a bit of what I read in Howard Barnum's entry, to try to find some sort of neat integration between the subjectivist approach and an objective reality (at least at some level).

It would seem, then, that the next step is to try to find out how to map the external requirement for non-contextuality on any purported features of the external reality. Is that correct? If it is, how do you intend to accomplish this? Also, your entry whetted my appetite for learning more about the philosophy of probability about which I know next to nothing (other than what I learned in your article). Can you recommend one or more introductory texts?

I have developed an original framework myself, and while it seems that it can reproduce major features of QM, I do not at present know how to get the Born Rule out of it. I strongly suspect that it is due to my ignorance in precisely this area, so I intend to change that.

I enjoyed your essay and wish you all the best,


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Author Matthew Saul Leifer replied on Jul. 14, 2013 @ 22:02 GMT
Thanks for your kind comments about my essay.

It is important to distinguish two things:

1) Believing in the subjective Bayesian interpretation of quantum theory and wanting to employ it in understanding the probabilities that arise in quantum theory.

2) Being a QBist, i.e. believing in what Caves, Fuchs and Schack have called quantum Bayesianism.

Quantum Bayesianism,...

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Armin Nikkhah Shirazi wrote on Jul. 15, 2013 @ 01:31 GMT
Dear Matthew,

Thank you for clarifying the distinctions. I looked at the reading list and it is far more extensive than I imagined. Thank you!


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john stephan selye wrote on Jul. 16, 2013 @ 15:39 GMT
Hi Matthew -

Your discussion of subjectivity is crucial to the subject of this contest. It is interesting to consider how we might apply the concept to an evolving observer, one who makes decisions at every moment, and over a very long period of time, during which his relation to the physical world - his own biological configuration, if you will - is continuously altered.

All conceivable decision scenarios are then possible, as you say in referring to It from Bit - 'with only certain subsets of all possible bets being jointly resolvable'.

If evolution affects us at every moment (and it is impossible to argue that it doesn't) then It from Bit is true: We live in a Species Cosmos that is being evolved from ourselves. However, it can and should be countered that we do seem to possess a certain objectivity - that Bits appear to be founded upon a reality greater than the continually evolving Species Cosmos - a reality where our logical and scientific parameters are less applicable, and often not applicable at all.

You might be interested to see how I treat this evolutionary argument as a realist interpretation of the field of reality, thus expanding the definitions of It and Bit far beyond those signified by Wheeler. I think you touch on this when you allude to '"it from bit from it", where the first "it" refers to classical ontology and the second refers to quantum stuff.'

I give this It-Bit-It sequence a structure you might find useful.

All the Best,


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Author Matthew Saul Leifer replied on Jul. 19, 2013 @ 13:29 GMT
Thanks for your comments. I think this is related to the longstanding debate about diachronic coherence in the literature on subjective Bayesian probability. Basically, the issue is about whether one can regard "you now" and "you at some point in the future" as one and the same agent. If you answer yes then it would be irrational to do something now that you believe with certainty that the future version of you will regard as irrational. Such kinds of argument are necessary to derive Bayesian updating as an rationality constraint. I have always been in the camp that regards diachronic coherence as unfounded. At most you can derive constraints on what you now expect that the future version of you will do, and not on what the future version of you actually should do. If this is the case then constraints on how probabilities evolve need to be grounded in physical reality rather than just rationality, but I believe that this point is already made just by considering alternative measurements at a single instant of time.

Antony Ryan wrote on Jul. 19, 2013 @ 11:57 GMT
Dear Matthew,

Excellent essay. I like the realist views and how you back up this approach. Moreover I really think you raise an excellent point and are dead right that we also need to consider the likes of wave fuctions, so it isn't a straightforward as It from Bit or vice versa.

Hopefully you'll get a chance to look at my essay, which I hope you find of interst too.

Best wishes & congratulations on your essay,


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Author Matthew Saul Leifer replied on Jul. 19, 2013 @ 13:18 GMT
Thanks for your comments. Being an advocate of the epistemic interpretation of the wavefunction, I don't actually think that the wavefunction is a viable contender for the fundamental ontology, but I mentioned it in the essay because it is an obvious counterexample to the idea that the "it" has to be made of things that we view as real in classical physics, like particles and fields. I believe that the "quantum stuff" is something more exotic that does not yet appear in contemporary interpretations of quantum theory.

Antony Ryan replied on Jul. 20, 2013 @ 22:49 GMT
Hi Matthew,

Exactly how I interpreted your essay. Well done on great work!


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Member Ken Wharton wrote on Jul. 19, 2013 @ 12:43 GMT
Hi Matt,

Excellent essay! I never know quite what to make of it when someone carefully reasons out an argument that (in the end) agrees with my reasoning, but clearly is far more detailed and careful than my own considerations. Did I really just get lucky through sloppy reasoning? Are both arguments merely rationalizations, trying to justify a previously-held common conclusion? Or had I...

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Author Matthew Saul Leifer replied on Jul. 19, 2013 @ 13:13 GMT
When attempting to argue against anti-realists, I think it is more effective to try and take all their assumptions on board and then show that it leads to a contradiction than to try and argue for realism a priori on the basis of what constitutes a "scientific explanation" or something like that. Of course, most realists will agree with such a priori arguments, but that is just preaching to the choir. An anti-realist is, by definition, someone who does not agree with such arguments and thinks that they have valid counterarguments, so they can just go ahead and adopt something Copenhagen-like anyway. If you want to persuade them then you have to argue on their home turf.

Regarding correlations that don't require a physical explanation, I would say that, technically speaking, the probabilities on a "semi-classical test space" are of this sort. This is where you just have N different betting contexts, each of which gets assigned its own independent classical probability distribution and there are no additional constraints. In this case, all the constraints are coming from the Dutch book argument, so they don't depend on any assumptions about a pre-existing reality. You may be inclined to reject such cases as uninteresting because they are only a slight modification of classical probability theory, but, as I mentioned in a footnote in the essay, such a system can be thought of as half of a nonlocal box, so interesting things can happen with such systems when we compose them. In fact, I would argue that the nonsignalling condition does have a viable physical explanation if one accepts fundamental Lorentz invariance, so in that case we could regard the PR-box correlations as an example of a set of probabilities that does not require additional physical explanation beyond what we already have.

Yutaka Shikano wrote on Jul. 20, 2013 @ 15:19 GMT
Hi Matt,

I really enjoyed reading your essay. While you defined the event space of subjective Bayesian probability as the discrete set, you mentioned about the Newtonian mechanics to seem to require the continuous event space. I a little confuse this point. How to explain that? Also, is there no difference or no technical or mathematical problem to extend the continues set from the discrete set? For example, considering functional analysis, there are many nontrivial examples to be satisfied in the continuous set but not in the discrete one and vice verse.

Best wishes,


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Author Matthew Saul Leifer replied on Jul. 20, 2013 @ 15:45 GMT
The example I gave from Newtonian mechanics does employ a continuous ontological state space, although we might imagine be betting on some coarse graining of that, in which case the event space would be discrete.

Nevertheless, there are of course additional issues that come up in the case of a sample space of infinite cardinality, even for a countably infinite space let alone the continuum....

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Cristinel Stoica wrote on Jul. 20, 2013 @ 18:59 GMT
Dear Matt,

I enjoyed very much your essay. It contains a very profound part on probabilities, but it is deep also from the viewpoint of physics and philosophy. Indeed, the standard view on probabilities should be reviewed and generalized, to allow "a bunch of probability distribution, rather than just one". What mysteries remain in quantum mechanics, after this revision is done?

I also like the angle your essay takes on the main theme of the contest, namely that 'it from bit' is compatible with your proposed 'bit from it' by the scheme "it-as-quantum-stuff => bit => it-as-particles-and-fields".

There are many points of your essay that I would like to understand better, so I intend to reread it, and also more of your writings in this direction.

Best regards,

Cristi Stoica

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Sreenath B N wrote on Jul. 21, 2013 @ 18:11 GMT
Dear Matthew Leifer,

I have down loaded your essay and soon post my comments on it. Meanwhile, please, go through my essay and post your comments.

Regards and good luck in the contest,

Sreenath BN.

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Than Tin wrote on Jul. 24, 2013 @ 22:44 GMT
Dr. Leifer

Richard Feynman in his Nobel Acceptance Speech (

said: “It always seems odd to me that the fundamental laws of physics, when discovered, can appear in so many different forms that are not apparently identical at first, but with a little mathematical fiddling you can show the relationship. And example of this is the Schrodinger equation and the Heisenberg formulation of quantum mechanics. I don’t know why that is – it remains a mystery, but it was something I learned from experience. There is always another way to say the same thing that doesn’t look at all like the way you said it before. I don’t know what the reason for this is. I think it is somehow a representation of the simplicity of nature.”

I too believe in the simplicity of nature, and I am glad that Richard Feynman, a Nobel-winning famous physicist, also believe in the same thing I do, but I had come to my belief long before I knew about that particular statement.

The belief that “Nature is simple” is however being expressed differently in my essay “Analogical Engine” linked to .

Specifically though, I said “Planck constant is the Mother of All Dualities” and I put it schematically as: wave-particle ~ quantum-classical ~ gene-protein ~ analogy- reasoning ~ linear-nonlinear ~ connected-notconnected ~ computable-notcomputable ~ mind-body ~ Bit-It ~ variation-selection ~ freedom-determinism … and so on.

Taken two at a time, it can be read as “what quantum is to classical” is similar to (~) “what wave is to particle.” You can choose any two from among the multitudes that can be found in our discourses.

I could have put Schrodinger wave ontology-Heisenberg particle ontology duality in the list had it comes to my mind!

Since “Nature is Analogical”, we are free to probe nature in so many different ways. And you have touched some corners of it.

Good luck,

Than Tin

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Héctor Daniel Gianni wrote on Jul. 24, 2013 @ 22:47 GMT
Dear Matthew Saul Leifer:

I am an old physician and I don’t know nothing of mathematics and almost nothing of physics, so is almost impossible for me to give an opinion in your essay. I this contest are many theories, mine is not.

Maybe you would be interested in my essay over a subject which after...

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Member Ian Durham wrote on Jul. 25, 2013 @ 22:08 GMT
Hi Matt,

This is a really thought-provoking essay. I'm in full agreement with your conclusion via-a-vis an underlying reality. However, if I'm reading your essay correctly, your definition of noncontextuality seems to differ a bit from the usual Kochen-Specker sense (Ken Wharton tells me you're further developing this?). In my own essay I proposed *contextuality* as a sort of underlying principle which I guess (?) would be in accord with the notion that noncontextuality must be derivable, but I think that assumes that we're using the terms in a similar sense. Could you elaborate on your notion of noncontextuality a bit?


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Author Matthew Saul Leifer replied on Jul. 25, 2013 @ 22:57 GMT
There is some subtlety surrounding the terminology of contextuality and noncontextuality, so let me distinguish two types. Gleason noncontextuality is the idea that a generalized probability measure on the set of quantum measurement outcomes should assign the same probability to outcomes that are represented by the same projector. From this assumption and Gleason's theorem we get the set of...

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Member Ian Durham replied on Jul. 26, 2013 @ 02:45 GMT
Thanks for the clarification. Personally I think there's more to the Kochen-Specker result than meets the eye. Or, rather, there's a really a third possible view of (non)contextuality that has a limited Bayesian subjectivity to it, i.e. there are degrees of dependence of the projectors on other projectors (if that makes any sense).

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eAmazigh M. HANNOU wrote on Jul. 29, 2013 @ 03:26 GMT
Dear Matthew,

One single principle leads the Universe.

Every thing, every object, every phenomenon

is under the influence of this principle.

Nothing can exist if it is not born in the form of opposites.

I simply invite you to discover this in a few words,

but the main part is coming soon.

Thank you, and good luck!

I rated your essay accordingly to my appreciation.

Please visit My essay.

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Richard N. Shand wrote on Jul. 30, 2013 @ 19:04 GMT
Dear Dr. Leifer,

I found your essay to be very lucid and informative! ! I particularly enjoyed the use of the Dutch book argument to explain subjective Bayesian probability.

A realist approach to physics is possible if quantum potential is construed as constituting "objectively existing external reality." Counterfactual assertions can be applied to all possible paths calculated by the Lagrangian, in which probabilities are bound globally in time.

Contextual information, on the other hand, arises from the conditional entropy of the observer, who is locally part of the path selection process. The observer iteratively generates knowledge by erasing the entanglement information that encodes the quantum potential. (See my essay "A Complex Conjugate Bit and It".) In a sense, then, contextuality and noncontextuality are two sides of the same coin acting in reciprocity with each other.

Best wishes,


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Peter Jackson wrote on Aug. 2, 2013 @ 09:47 GMT

I've just re-read your essay in a 'round up' and confirm my initial favourable impressions. I think it very relevant and complimentary with mine, particularly the Bayesian interpretation, and "there is something wrong with our basic framework for realist models of quantum theory. The right framework ...should reveal that quantum theory is not nonlocal after all.!!"

I'm sad you haven't read mine, but note you choose mainly by abstract. I'm told my dense abstract has put some off. I hope I may persuade you to ignore it in this instance by quoting from my blog posts, which include;

"groundbreaking", "remarkable!", "clearly significant", " fantastic job", "wonderful essay", "deeply impressed", "valuable contribution", "Technically challenging and philosophically deep", "Rubbish", etc. (ok, I made that last one up!).

I hope you don't judge my book by it's cover as I think we may even be on the brink of an important step forward, or even quantum leap!.

Best wishes


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Peter Jackson wrote on Aug. 3, 2013 @ 19:23 GMT
Dear Matt,

My admiring post, comments on commonality and 'thought experiment' seemed to upset you (July 5th). I sincerely apologise if it did. You say you mainly use abstracts to select essays to read. In my case this may be wrongly judging a book by it's cover. A few have said the abstract is too dense but the essay excellent, indeed blog comments include; "groundbreaking", "clearly significant", "astonishing", "fantastic job", "wonderful", "remarkable!", "deeply impressed", etc.

I do hope I can prevail on you to check it over and offer any views and advice.

Thank you kindly and very best wishes


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Peter Jackson replied on Aug. 4, 2013 @ 16:51 GMT
Aha! The lost posts are returning from wandering in cyberspace! Sorry about the repeat.


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eAmazigh M. HANNOU wrote on Aug. 4, 2013 @ 18:32 GMT
Dear Matthew,

We are at the end of this essay contest.

In conclusion, at the question to know if Information is more fundamental than Matter, there is a good reason to answer that Matter is made of an amazing mixture of eInfo and eEnergy, at the same time.

Matter is thus eInfo made with eEnergy rather than answer it is made with eEnergy and eInfo ; because eInfo is eEnergy, and the one does not go without the other one.

eEnergy and eInfo are the two basic Principles of the eUniverse. Nothing can exist if it is not eEnergy, and any object is eInfo, and therefore eEnergy.

And consequently our eReality is eInfo made with eEnergy. And the final verdict is : eReality is virtual, and virtuality is our fundamental eReality.

Good luck to the winners,

And see you soon, with good news on this topic, and the Theory of Everything.

Amazigh H.

I rated your essay.

Please visit My essay.

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Charles Raldo Card wrote on Aug. 6, 2013 @ 03:44 GMT
Late-in-the-Day Thoughts about the Essays I’ve Read

I am sending to you the following thoughts because I found your essay particularly well stated, insightful, and helpful, even though in certain respects we may significantly diverge in our viewpoints. Thank you! Lumping and sorting is a dangerous adventure; let me apologize in advance if I have significantly misread or misrepresented...

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Torsten Asselmeyer-Maluga wrote on Aug. 6, 2013 @ 12:02 GMT
Dear Matthew,

very interesting point of view. I completely agree that quantum mechanics enforces us for a new probability theory. von Weizsäcker was one of the first who noticed it. Maybe have a look into my essay?

It is a more geometrical point of view. I think that the structure of the spacetime determines a lot.

Best wishes


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Stephen James Anastasi wrote on Aug. 6, 2013 @ 12:32 GMT
Hello Matthew

I found your discussion of Bayesianism quite fascinating. You said that there is nothing in logic that tells you what premises you have to start with.

In my essay, one begins with all possible propositions. How this connects with yours, I am not quite sure yet. Logic is subjugate to the General Principle of Equivalence, as is every proposition, and the GPE filters out all propositions but two at the first step.

I found the last parts quite hard to follow, but liked the main theme.

Best wishes

Stephen Anastasi

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Member Howard N Barnum wrote on Aug. 7, 2013 @ 23:11 GMT
Really excellent essay, Matthew, one of the very best here.

I'm not sure I'd agree that quantum theory represents a situation in which there is a failure of the normative force of standard probability theory... I think that whatever normative force it has still holds within contexts, and shouldn't be expected to hold across contexts, so I prefer not to say that quantum theory(and other...

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Author Matthew Saul Leifer replied on Aug. 8, 2013 @ 13:09 GMT
"I'm not sure I'd agree that quantum theory represents a situation in which there is a failure of the normative force of standard probability theory"

It is pretty important for me to view things this way from a rhetorical point of view, even if it does not make much difference to the mathematics. The reason is that many Bayesians seem to think that their derivations of probability theory...

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Member Howard N Barnum replied on Aug. 8, 2013 @ 23:11 GMT
Matt, I'd love to see your derivation of probabilities in an Everett-style theory sometime. When you write:

"For example, Adrian Kent's argument that the amplitudes are just "numbers in the sky" which should not constrain rational decision making is avoided by saying that amplitudes do not constrain probabilities (only the branching structure does)."

I think Adrian's objection is...

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Paul Borrill wrote on Aug. 8, 2013 @ 00:18 GMT
Dear Matthew - My goal was to review and rate every single essay on this site. I thought I had finished a few hours ago, but my assistant just checked off the whole list, and discovered that I had missed you. I will fix this and review it now (may take me an hour or more to do a good job). I promise I will get a rating in before the contest closes in 3 1/2 hours from now. From skiming through it quickly, I can already tell it looks good, but in the spirit of academic integrity, I need to read it properly in order to rate it accurately.

In the meantime, I suspect you were not even aware of my essay, in which case, I would be honored if you would take a look at it.

You can find the latest version of it here:

(sorry if the fqxi web site splits this url up, I haven’t figured out a way to not make it do that).

Kind regards, Paul

p.s. I will delete and replace this message with my actual comments later.

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Paul Borrill wrote on Aug. 8, 2013 @ 03:16 GMT
Matthew - yours was the last of the over 180 essays I reviewed. I apologize for overlooking it earlier.

As the wormhole is about to close ... this is a superb piece of work, clearly one of the most outstanding essays on this site.

It would appear to go hand in hand with the essay by Mark Freely: a beautiful explication of what probability theory means, and how we (as physicists) abuse the mathematics without quite knowing what it means.

As a realist, I totally resonated with your conclusion: extra physical principles are needed in the agent-independent reality in order justify the faith we have in probability.

Well done. I believe this is a major contribution to the debate.

Kind regards, Paul

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Héctor Daniel Gianni wrote on Aug. 10, 2013 @ 22:18 GMT
Dear Matthew Saul Leifer:

I am an old physician and I don’t know nothing of mathematics and almost nothing of physics, so is almost impossible for me to give an opinion in your essay. In this contest are many theories, mine is not.

Maybe you would be interested in my essay over a subject which after the common people, physic discipline is the one that uses more than any other, the...

view entire post

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Jayakar Johnson Joseph wrote on Nov. 2, 2013 @ 17:14 GMT
Congratulations, dear Leifer.

I think constrains on generalising the probability theory is with Frequency probability, while non-zero intervals of events is subjective.

In this context, quantum probability needs quantization of time, in that cyclic-time emerges subjectively without uncertainty of events. This is conclusive while matters comprised of eigen-rotational string-like structures rather than point-like particles, in that time emerges with the eigen-rotation of sting-matter segment.

Thus I think the subjective Bayesian interpretation is applicable for the time quantisation in this string-matter continuum scenario, as it evolves probability from prior probability.

With best wishes,


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