I recently read an interesting book on reality, entitled The Fabric of Reality. In the book, David Deutsch constructs a unified theory of reality by combining four fundamental theories:
1. Quantum mechanics (multiverse interpretation).
2. Turing principle of computers and artificial intelligence.
3. Popperian epistemology.
4. Darwinian evolution.
In all cases the theory that now prevails, though it has definitely displaced its predecessor and other rivals in the sense that it is being applied routinely in pragmatic ways, has nevertheless failed to become the new ‘paradigm’. That is, it has not been taken on board as a fundamental explanation of reality by those who work in the field.
Thus practitioners may reject the multiverse, which Deutsch regards as the straightforward explanation of quantum mechanics. Or they may deny that a machine could replication a human brain. Or they may argue for “exceptions” to evolution, such as punctuated equilibria. Or they may argue that Popperian epistemology has a “problem of induction” and create alternative models such as the Kuhnian explanation of scientific progress.
Unlike many others, Deutsch takes the straightforward interpretation of these 4 theories quite seriously:
My thesis, therefore, also takes the form ‘the prevailing theory is true after all!’ . . .
I have also argued that none of the four strands can be properly understood independently of the other three. This is possibly a clue to the reason why all these prevailing theories have not been believed. All four individual explanations share an unattractive property which has been variously criticized as ‘idealized and unrealistic’, ‘narrow” or ‘naive’ — and also ‘cold’, ‘mechanistic’ and ‘lacking in humanity’.
[Note: When Deutsch says: “the reason why all these prevailing theories have not been believed”, I believe he means the straightforward interpretation of these theories have not been believed. See the first quote above.]
Deutsch is doing something quite strange. He’s claiming to be a contrarian because he accepts a straightforward explanation of all four standard models. I don’t have enough expertise to evaluate his views on the nature of reality, but these comments reminded me of many of the disputes that I see in economics. Hypotheses such as the Efficient Markets Hypothesis and Rational Expectations lie right at the center of modern finance and macroeconomic models. And yet many economists claim not to believe these theories. They regard them as ‘idealized and unrealistic’, ‘narrow” or ‘naive’.
Like David Deutsch, Paul Krugman found himself playing the role of being a rebel, merely by defending the standard model of comparative advantage:
There is nothing that plays worse in our culture than seeming to be the stodgy defender of old ideas, no matter how true those ideas may be. Luckily, at this point the orthodoxy of the academic economists is very much a minority position among intellectuals in general; one can seem to be a courageous maverick, boldly challenging the powers that be, by reciting the contents of a standard textbook. It has worked for me!
But to many non-economists, and even some economists, concept such as comparative advantage and creative destruction can seem (to quote David Deutsch):
‘idealized and unrealistic’, ‘narrow” or ‘naive’ — and also ‘cold’, ‘mechanistic’ and ‘lacking in humanity’.
At times, I find myself in a small minority simply by defending the standard model. I argued that the 2000 tech stock boom and the 2005 house price boom were not bubbles, because the EMH says that bubbles do not exist. People have rational expectations regarding the future path of asset prices. I really believe that.
Or take the standard model of money, spending and the business cycle:
1. Monetary policy determines the path of nominal spending, at least when interest rates are positive.
2. A crash in nominal spending would cause a severe recession.
3. NGDP growth plunged dramatically during 2008, at a time when interest rates were not stuck at zero.
So . . . what is the straightforward interpretation of these three uncontroversial claims? I argued that this suggests the Fed caused the Great Recession with a tight money policy that drove NGDP growth from positive 5% to negative 3%. But almost no one accepts my claim.
“Yes, that’s what the model suggests, but it sure didn’t look like the Fed caused the recession.”
I feel a bit reassured that people much smarter than me run into the same resistance:
“Yes, Ricardian theory suggests that the US benefits from imports, but it sure feels like they hurt our economy.”
“Yes, the EMH suggests that the stock market is efficiently priced, but it sure looks like there are periods of irrational exuberance.”
“Yes, quantum mechanics seems to suggest that there are a dizzying number of universes, but that seems implausible.”
“Yes, the Turing Principle suggests that a computer could have human-like consciousness, but my own consciousness seems sort of special, not merely mechanical.”
Mar 7 2023 at 3:33pm
I agree that there’s a correspondence between you and Deutsch.
I have two degrees in economics, but macro never really seemed coherent to me.
I was in software in the 90s and as soon as I was exposed to the Deutsch paradigm, I quickly concluded that this was obviously correct. But for some reason, most people were adopting epicycles to avoid acknowledging the obvious.
Then when I was started reading your blog in the late 2000s, I had exactly the same mental feeling.
Mar 7 2023 at 4:22pm
I can echo essentially the same experience as Kevin.
Mar 7 2023 at 5:00pm
Full disclosure: Don and I have been friends since college, so these datapoints are not independent. Though we did come to follow your blog independently.
Mar 7 2023 at 8:48pm
I know of Turing test but i hadn’t heard of Turing principle.
All these interpretations of quantum mechanics, strong AI etc are quite contentious within the field. For example, the multiverse is not widely accepted, leaving aside basic philosophical problems associated with it.
Mar 7 2023 at 4:21pm
That seems reminiscent of another famous quote:
Mar 8 2023 at 4:57pm
I used that quote at the very beginning of my book “The Money Illusion”.
Knut P. Heen
Mar 10 2023 at 9:11am
I use the Wittgenstein quote as an introduction to one of my business economics classes (before I start talking about the virtue of profits).
Mar 7 2023 at 4:49pm
re: continuous creation
Thankfully, God keeps the order by creating new things that appear like the things that existed before in their place. This a few centuries earlier from the Sufi Al-Ghazali:
Motion, like time, is an illusion of the mind.
Mar 7 2023 at 7:28pm
“my own consciousness seems sort of special”
Seems special to whom or to what? If there is no consciousness or soul outside the computable processes of the physical brain, then what is the thing that is supposedly being fooled into thinking that it is “special”?
Mar 8 2023 at 8:14am
That is begging the question.
Mar 7 2023 at 8:52pm
I am not sure if Darwinian evolution belongs to any list that has multiverse. Except for the American sect of Intelligent Design, the Darwinian evolution is universally accepted and used by the biologists.
Mar 8 2023 at 8:16am
As mentioned in the article, punctuated equilibrium is non-Darwinian.
Mar 8 2023 at 8:58pm
Is it? Punctuated equilibrium is just the proposition that evolution is characterized by long periods of stasis.
It refers to the pattern of long-term evolution but does not deny the fundamental Darwinian evolution.
Mar 9 2023 at 5:59am
Punctuated equilibrium is actually a straightforward prediction of Darwinian evolution: natural selection will tend to optimize organisms to a given environment such that any further mutations will not be favorable. There might be organismal designs that are better, but the mutational path to get there would require transitional forms that are less fit. Thus, the central problem of evolution is how populations manage to “travel” from one adaptive peak to the next one. When this happens, it’s usually too fast to leave much of a fossil record.
Mar 8 2023 at 11:57am
There’s still some reluctance to accept Cochran’s theory that Ashkenazi IQs have been influenced by recent evolution.
I often suspect that medical researchers pay too little attention to questions about why evolution would allow the existence of the problem they’re focused on.
Mar 7 2023 at 10:09pm
David Deutsch constructs a unified theory of reality by combining four fundamental theories…
Which, remember, have no explanation for 95% of the universe (dark matter and dark energy) — and until the 1990s didn’t even know that they didn’t know about 75% of the universe. Also, the two best theories of the universe, general relativity and quantum mechanics, flatly contradict each other where they intersect, so one or both be seriously wrong. And science has zero explanation for consciousness and a whole lot of other very basic things I could list… So maybe a bit of modesty is in order when constructing “unified theories of reality”?
Thus practitioners may reject the multiverse, which Deutsch regards as the straightforward explanation of quantum mechanics… Unlike many others, Deutsch takes the straightforward interpretation of these 4 theories quite seriously: “My thesis, therefore, also takes the form ‘the prevailing theory is true after all!” .
That was the deal pre-Copernicus & Galileo, and pre-Einstein. Worked well enough back then. What could go wrong now? It’s not like there are any big problems in our most important theories. 🙂
Or maybe this is a case where the expert professional “practitioners” are right? I’ll establish my woke cred by pointing to one of the world’s leading female theoretical physicists…
The Multiverse: Science, Religion, or Pseudoscience?
Sabine points out that now there are more than nine different multiverse theories. And growing! Why? Because, have a problem you don’t understand — the wave function, basic constants — don’t say “we don’t understand yet”, say: Multiverse! We’re just in the appropriate multiverse. Done.
She points out elsewhere that scientists, being human, are quite fond of “the god of the gaps” fallacy. Don’t know why the sun rises or storms blow: the gods. How the eyeball could be formed: God. But they don’t like to say “god” so they say “multiverse” to the same effect.
My favorite example is how we live in “simulation multiverses ” as pushed by Nick Bostrom, Neil deGrasse Tyson, et. al. This solves all the mysteries of our existence because the simulations are run to create us. Very logical! And who is running the base root simulation creating our universe amid all the other multiverses? God, maybe in his parents’ basement.
“Yes, Ricardian theory suggests that the US benefits from imports, but it sure feels like they hurt our economy.”
That’s just basic, banal, low-level generic human thinking. It will be endemic forever.
“Yes, quantum mechanics seems to suggest that there are a dizzying number of universes, but that seems implausible.”
That’s one of the world’s leading female theoretical physicists being polite about it, plus most quantum physics “practitioners”, calling out pop “pseudo science” (she said it, not me!) and their peers who foster it.
I see and sympathize with the point you are making, but think this is not the best illustration of it. Ricardian theory explains and predicts many important things accurately. Multiverses explain as well as “god” — and predict absolutely nothing.
Mar 7 2023 at 10:18pm
I mean, dang, even Modern Monetary Theory made predictions!
Mar 7 2023 at 11:34pm
You seem to be confusing “multiverse” speculations with the “Multiple Worlds Interpretation” of quantum mechanics (aka “decoherence”). They aren’t at all the same thing.
Mar 8 2023 at 9:26am
Best explanation why many worlds interpretation is not science. It is the description of a subjective interpretation, that can’t be objectively verified and adds nothing to the science. Just one of many place holders, masquerading as a solution to our ignorance about the unsolved measurement problem.
Mar 7 2023 at 10:21pm
The West followed the wrong Greek. It’s been wrong about reality ever since.
Mar 8 2023 at 2:17am
Physical theories are devised to explain and understand change–myriad changes that occur in material bodies.
Thus, it would be a logical error for a physical theory or interpretation thereof to deny change altogether.
Mar 8 2023 at 10:28am
re: “the Fed caused the Great Recession” Damn straight.
Capt. J Parker
Mar 8 2023 at 11:13am
I believe Scott Sumner when he says the Fed caused the great recession with a tight money policy. But,
One reason money was tight was because there was a increased demand for cash because mortgage backed securities values were collapsing.
Perhaps the Feds interest rate increases in 2004-2006 set the collapse of mortgage bonds in motion.(the rate increases surely correlate with a drop in housing starts) But,
What the heck kind of a risk model would you have to use for an asset price to collapse due to a Fed Funds rate increase from 1% in mid 2004 to 5% in mid 2006 given that for 30 years prior to 2001 Fed Funds rate had never gone below 3%?
Maybe the low rates of 2001 to 2004 created mispricing of mortgage bonds and preordained their collapse.
But, If EMH were true then markets should have a stabilizing effect on the macro economy.
In the case of MBS, the market for them certainly seems destabilizing.
My conclusion – Believing that the Fed caused the great recession or that deviations in the path of NGDP can cause recessions is not a sufficient condition for EMH to be true.
Mar 8 2023 at 1:50pm
re: “My conclusion – Believing that the Fed caused the great recession or that deviations in the path of NGDP can cause recessions is not a sufficient condition for EMH to be true.”
Exactly. And the Ph.Ds. at the FED still don’t know a debit from a credit.
The “money multiplier”, or required reserves was 106:1. Draining reserves for 29 contiguous months destroyed the means-of-payment money supply causing the GFC.
Mar 8 2023 at 2:54pm
The trouble with the example of quantum mechanics is that the many-worlds interpretation is not the dominant view among physicists and never has been. The dominant view is the Copenhagen interpretation. That’s what’s been taught in textbooks since it emerged as dominant in the 30s or 40s. That’s quite different than evolution by natural selection, which nearly every biological scientist accepts, or even the textbook macroecon models you refer to. Many-worlds never made it into textbooks, except for mere mentions.
Most physicists think string theory is the most promising next general theory of physics, and it can be interpreted as predicting a multiverse, but not the many worlds version.
Then, you have cosmic evolutionary theories….
But, I could be wrong, given that I’m not a physicist.
Mar 8 2023 at 5:01pm
“The trouble with the example of quantum mechanics is that the many-worlds interpretation is not the dominant view among physicists and never has been.”
Yes, but that’s the whole point of Deutsch’s example. So it’s not the “trouble” with using it as an example.
Mar 8 2023 at 11:09pm
“In all cases the theory that now prevails, though it has definitely displaced its predecessor and other rivals in the sense that it is being applied routinely in pragmatic ways”
Which is precisely not the case with many-worlds interpretation (which is again distinct from multiverse theory, which is not an interpretation of quantum mechanics) .
The many-worlds interpretation has not displaced the Copenhagen interpretation (just check textbooks) and neither it is routinely applied. Interpretations of quantum mechanics are not in the business of being applied ( quantum mechanics is what is applied).
Mar 9 2023 at 2:17pm
He’s saying that the multiverse approach is the straightforward interpretation of QM, but most physicists don’t believe it. But they do accept the model in a technical sense. As an analogy, recall when the Church wanted Galileo to claim that his model was merely predictive, and didn’t describe the reality of the Solar System.
Mar 9 2023 at 11:48pm
He’s saying that the multiverse approach is the straightforward interpretation of QM, but most physicists don’t believe it.
Right. They believe there are other, better, interpretations of QM — Deutsch’s modest opinion that his own is “the” interpretation of QM as opposed to “an” interpretation notwithstanding. From a long Less Wrong post on a conference on cosmology discussing the multiverse….
This commenter’s science opinions aside, his objective count of how many premier physicists respect the multiverse squares exactly with Sabine’s, “there are very, very few people working on it. It’s fringe.” But why???
As an analogy, recall when the Church wanted Galileo to claim that his model was merely predictive, and didn’t describe the reality of the Solar System.
So, the populist uneducated mob is again stifling the best minds of science, as per Galileo and Ricardian comparative advantage ideas? No … the opposite!
The populist uneducated mob loves multiverses, the more the better. It is best minds of science that say “no”. But why?
But they do accept the model in a technical sense.
No. They use QM (not “the model”) constantly in a very practical sense. Nobody uses the “multiverse interpretation” at all for anything. How could they? It does not observe our universe and so makes no falsifiable predictions. As Penrose said, “It’s pointless”. THAT’S why almost all physicists prefer other interpretations that are potentially testable, as they relate to our real world. As Galileo’s and Ricardo’s observations did.
Sabine interviews Deutsch in her recent book, Existential Physics. They’re friendly. Check it out. This argument is not such a big deal.
I looked up reviews of Deutsch’s book, mostly very positive, “imaginative … informative … engaging”, also with frequent use of the word “speculative”, such as ….
If that’s the future he deduces from his “unified theory”, I’m all for it!
Mar 9 2023 at 12:18am
Deutsch says:“In all cases the theory that now prevails, though it has definitely displaced its predecessor and other rivals in the sense that it is being applied routinely in pragmatic ways, has nevertheless failed to become the new ‘paradigm’. “”
This is definitively not true as to “1. Quantum mechanics (multiverse interpretation).” If the former video wasn’t good enough for you, here are Nobelist Roger Penrose, Michio Kaku, and Sabine discussing the matter..
The 53 minutes In brief… Michio spends his time defending the declining reputation of string theory, leaving Penrose repeatedly asking: “What’s that got to do with the multiverse?” (At minute 27:15) The moderator asks, “What difference is there between the multiverse proposal and the traditional explanation of God”? (At 36:20) Penrose is politely semi-snarky about the multiverse all the way through. Several: “I’m confused.” E.g., at 38:00: Is the multiverse proposal trying to eliminate the uncertainly in quantum mechanics that made Einstein uneasy? “If so, it’s not very impressive.” What makes the concept of the multiverse appealing? “I have no idea”. Laughter.  Sabine, next: “It’s appealing in the media and for selling books, but if you actually look in the physics community, there are very, very few people working on it. It’s a fringe part. It’s not in any meaningful way popular in physics.”
Hmm … in Economics terms that seems a lot like Modern Monetary Theory. How does it square with “it has definitely displaced its … rivals in the sense that it is being applied routinely in pragmatic ways” ?
IIRC you like philosophy, so here’s a question for you. How does one “apply routinely in pragmatic ways” a concept that does not apply to our universe and makes no falsifiable predictions of any kind?
Again, I sympathize very much with the argument you are making. But to embrace the over-popularized, fringe, physics equivalent of MMT over the objections of Nobel winners and top professionals looks like engaging in the very behavior you are protesting against in economics.(Penrose/Krugman, Sabine/you, physics/econ)
Mar 8 2023 at 3:09pm
I should clarify and say that, many Copehagen interpretation proponents, including Bohr himself, argued that the many worlds interpretation resulted from a misunderstanding of basic quantum theory. They are argued that it could not be true.
Mar 8 2023 at 9:12pm
“it has not been taken on board as a fundamental explanation of reality by those who work in the field. ”
This is entirely absurd as applied to Darwinian evolution. All working biologists routinely treat Darwinian evolution as fundamental explanation of reality. Except for the tiny American sect of Intelligent Design.
” the theory that now prevails, though it has definitely displaced its predecessor and other rivals in the sense that it is being applied routinely in pragmatic ways,”
It is also absurd as applied to multiverse interpretation. Indeed there is nothing called multiverse interpretation of quantum mechanics. There is many-worlds interpretation and the multiverse theory is quite separate and answers quite different questions.
Mar 8 2023 at 11:18pm
I am mystified by this Turing Principle or Turing theory “that suggests that computer could have human-like consciousness”.
I know merely of a Turing test which is essentially behavioral and thus has nothing to do with consciousness. And it is a test for intelligent-seeming behavior of a computer, not an expectation or principle that computer could be intelligent-seeming.
Mar 10 2023 at 1:29pm
I think for Turing himself, if a computer was intelligent-seeming enough, it was conscious.
Mar 10 2023 at 1:50pm
Speaking of unification, I think it would be fun to unify Darwinism with cosmology. If you just look at the universe, it seems awfully well-designed to be able to produce life, and eventually intelligent life. There’s a gap for you. The two main explanations are God, and the multiverse: there were multitudes of universes, and only one or a relative tiny few were suitable for life, and so here we are as a matter of random chance.
Still that begs the question: you find a watch on the beach, there had to be a watchmaker. Similarly, when you look at an organism, it is obviously so well-designed that there also must be a watchmaker, but the blind watchmaker of natural selection suffices.
Now, it could be the case that universes within the multiverse give rise to other universes. If so, some universes probably will be better at reproduction than other universes. Thus the possibility of natural selection is set up.
It could further be the case that universes suitable for intelligent, technological life are especially good at reproducing. Consider truly being able to understand how the Big Bang happened in detail. That would imply the knowledge of how to make a new universe, would it not? And since when did humans come up with a theoretical invention that they didn’t try to instantiate?
Thus, it could be that Homo sapiens constitutes the “germ line” of the universe, and that it is our eventual, God-like destiny to create a new universe before ours dies naturally of its inevitable heat death.
You heard it here first! 🙂
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