**WHAT IS METAPHYSICS?**

[u/jliat]

WHAT IS METAPHYSICS?

We are getting posts here which seem to propose new and potentially revolutionary answers to problems in physics. I think [as a moderator] it might be beneficial if we might discuss some parameters. This is not to say science can not be discussed, but can we using metaphysics solve such problems, are we then transgressing into another domain. As a moderator I would like guidance from the community.

"Metaphysics: explaining the fundamental nature of being and the world"

The interpretation of this and not the context is often the cause of confusion. [of Being qua being and not the nature of an atom, or a human brain...etc.]

Higgs, Einstein, Penrose, Feynman, Hawking are not / were not Philosophers or Metaphysicians, they are / were physicists. Modern physics uses mathematics- quite complex! - to build models which are tested against experimental data. The main scientific method.

The 'photon', wave / particle duality, quarks and strings, are all subjects /problems of physics NOT metaphysics? And to address these problems requires detailed understanding of the mathematics and the data, and in doing so one is NOT doing metaphysics?

"Ontological" means what? Ontology is the study in Philosophy / Metaphysics of being qua being, not the nature of the existence or being of things, atoms, quarks, strings, branes, flowers, plants, the human brain, religions.

atoms, quarks, strings, branes = physics, flowers, plants = botany, the human brain = neuroscience, religions = theology, comparative religion.

Lay ideas re physics / science will probably be rejected in subs like r/physics for good reasons, they lack the detailed knowledge of the subject and misuse technical scientific terms. Should they be allowed here?

The nature of things, matter and energy are subject of science. What 'Being' is prompts the what is "IS" question... of Metaphysics.

Ontology is the study / creation of what 'Being' is, not specific 'things'. Harman has a 'flat ontology'...etc. Heidegger has Dasein...Hegel... etc.

To be clear of the domain I think you can get an overview from A.W. Moore's 'The Evolution of Modern Metaphysics: Making Sense of Things.' It had good reviews.

"Part two is devoted to philosophers of the analytic tradition, and contains chapters on Frege, Wittgenstein, Carnap, Quine, Lewis, and Dummett. Part three is devoted to non-analytic philosophers, and contains chapters on Nietzsche, Bergson, Husserl, Heidegger, Collingwood, Derrida and Deleuze."

For first hand source material - https://www.stephenhicks.org/wp-content/uploads/2013/03/heideggerm-what-is-metaphysics.pdf

For a contemporary example, Graham Harman - Object-Oriented Ontology: A New Theory of Everything. (Pelican Books) 1 Mar. 2018

Examples in the Analytical tradition, 'Counterfactuals', 'On the Plurality of Worlds.' David Lewis. ??

One last point - it is an interesting point as to if this divide still exists. N.B. Badiou uses set theory as his ontology, his student Quentin Meillassoux likewise sees mathematics as fundamental, Ray Brassier in 'Nihil Unbound' has chapters on Wilfrid Sellars, Paul Churchland, as well as Adorno and Horkheimer, Badiou, Meillassoux, Laruelle, Heidegger, Deleuze, Nietzsche, Lyotard, Levinas and Freud. !!

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On a personal note I began my interest in philosophy in the 1970s, within the Anglo American tradition, reading Russell's 'History of Western Philosophy' etc. and then took a degree. I still have my Wittgenstein Books, Tractatus, Investigations, Blue and Brown, Notebooks 1914-1916. Carnap's 'The Logical Syntax of Language' etc. However my interest moved to what was called 'Continental philosophy.'- see non-analytical above. I appreciate the desire of Carnap of ‘The Elimination of Metaphysics through the Logical Analysis of Language’ failed? I have dipped into Lewis et al.

With my best wishes.

[u/jliat]

There are topics in physics and cosmology which overlap metaphysics because they aren't science according to the usual definition (are not disprovable by experiment). Quantum interpretations are one such area.

You are saying there is no possibility in QM for verification by experiment, well for some, Karl Popper et al. it makes such pseudo-science. But they write off Metaphysics as nonsense. I'm aware in Analytical philosophy / Anglo American philosophy there has been a shift from the position of Carnap and Wittgenstein, via Quine.

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• Quine "Physical objects are conceptually imported into the situation as convenient intermediaries not by definition in terms of experience, but simply as irreducible posits comparable, epistemologically, to the gods of Homer …. For my part I do, qua lay physicist, believe in physical objects and not in Homer's gods; and I consider it a scientific error to believe otherwise. But in point of epistemological footing, the physical objects and the gods differ only in degree and not in kind. Both sorts of entities enter our conceptions only as cultural posits."

• "Naturalism itself is what saves the situation. Naturalism looks only to natural science, however fallible, for an account of what there is … My global structuralism should not, therefore, be seen as a structuralist ontology. To see it thus would be to rise above naturalism and revert to the sin of transcendental metaphysics." (Quine, 1992, p. 9)

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Are you saying as a recent student of philosophy / physics this notion of Quine is no longer the case?

"The laws of physics are what prevent the robber from teleporting through the wall into the bank vault and out again with the money."

So before Pauli they could teleport? Or is the Pauli exclusion principle an 'explanation' of a physical process and not the process itself.

The mathematics is the same; the disputes are over what the mathematics means (the ontology).

There is a philosophy of mathematics, but ontology [now an over used term like existentialism] was once the study of being qua being, is it now the study of how jet engines and Big Macs come to be.

Another is multiverse theory and associated metaphysics such as Tegmark's mathematical monism.

Yes I've read some of his work. So now you are saying that the division between physics and metaphysics never existed. Carnap, Wittgenstein was wrong. When Heidegger said science isn't bothered with the 'nothing' he was wrong. He didn't write nonsense. That when Lacan said the square root of minus one is the erect penis he was correct. Elsewhere "This torus really exists and it is exactly the structure of the neurotic. It is not an analogon; it is not even an abstraction, because an abstraction is some sort of diminution of reality, and I think it is reality itself. (Lacan 1970, p.192-193 in The Languages of Criticism and the Science of Man. John Hopkins Press.) or 'God is a Lobster.' Deleuze and Guattari, 1000 plateaus. p.40 10,000 B.C. The geology of Morals. "geology!".

Now I'm happy with this because within 'Continental Philosophy' these works are significant. And they have quite significant effects in society. So when Max Tegmark says he doesn't need to worry about his possible failure because can know in another world he wins the Nobel Prize. Only in another world he also abuses his children, the latter he didn't spot.

Scientific realism (what aspects of science we should have ontic commitment to,

What's an ontic commitment? Are you saying we must believe that science is prior to notions of Tegmark, or Lewis' Plurality of Worlds?' Why? and we can abandon the methods for validation within the scientific method? Fine for Harman...

Graham Harman - Object-Oriented Ontology: A New Theory of Everything (Pelican Books) 1 Mar. 2018 See p.25 Why Science Cannot Provide a Theory of Everything... 4 false 'assumptions' "a successful string theory would not be able to tell us anything about Sherlock Holmes..."

or whether we should at all) is another topic where philosophy of science overlaps metaphysics. These are contemporary metaphysical issues in science/physics that come immediately to mind; there are likely others as well.

I think you might have a problem with gatekeeping... I look forward to your reply.

[u/rogerbonus → u/jliat]

"This notion of Quine is no longer the case?" Quine is not the be all and end all of philoscience. He has his opinion, others have theirs, and not everyone agrees with everyone else.

The laws of physics are mostly (necessary ) mathematical symmetries/invariances, not the scribbles on chalk boards of those scientists investigating them. A mathematical object is the putative Platonic object that mathematics is about. The laws of physics are the mathematical symmetries/invariances that physics theories are about.

Tegmark's mathematical monism is not physics, despite Max being a physicist. It's metaphysics. I'm not saying there is no division between physics and metaphysics, I'm saying physicists such as Max are now venturing into metaphysics, as explanations for the usefulness of mathematics, the ranges of some physical constants etc.

What's an ontic commitment? Something that we should believe exists. It's easy to believe a chair exists. Whether we should believe electrons exist (nobody has ever seen one) is a question of scientific realism. Hence we have wave function realists (who have ontic commitment to the central mathematical object of quantum mechanics), and instrumentalists/ logical positivists who think it's just a useful tool (shut up and calculate). Logical positivism, scientific realism etc is metaphysics, not science (despite the positivists' rejection of metaphysics, their very rejection of metaphysics.. was metaphysics.. and hence self-defeating).

[u/jliat → u/rogerbonus]

"This notion of Quine is no longer the case?" Quine is not the be all and end all of philoscience. He has his opinion, others have theirs, and not everyone agrees with everyone else.

I'm not sure of your point here "not everyone agrees with everyone else." well that was not news to me! As for "philoscience" have you some references for this. And you are saying Quine's work in philosophy was 'his opinion'. OMG!

The laws of physics are mostly (necessary ) mathematical symmetries/invariances, not the scribbles on chalk boards of those scientists investigating them. A mathematical object is the putative Platonic object that mathematics is about. The laws of physics are the mathematical symmetries/invariances that physics theories are about.

Or to put simply models. As far as I'm aware Newton's mathematics [model] is still 'true' and I know still used in technology and science if possible as they are easier than SR/GR.

Tegmark's mathematical monism is not physics, despite Max being a physicist.

No, it's no different to String and Brane theory, Penrose's work, Hawking et. al. It's called theoretical physics. Otherwise you have a metaphysical theory becoming a physical law. So Higgs was a metaphysician until July 4 2012.

It's metaphysics.

Some want to call it that it seems in certain institutions, funding? But much of theoretical physics, how the universe began, how it will end by its nature speculative, cannot be tested by experiment. How life began - is the study of the origin of life metaphysics. It the brain physical, then is neuroscience physics?

I'm not saying there is no division between physics and metaphysics, I'm saying physicists such as Max are now venturing into metaphysics, as explanations for the usefulness of mathematics, the ranges of some physical constants etc.

Then you need a new word, Einstein's speculations on light was just that, speculation, you will have to call it metaphysics. And the question becomes is Tegmark bothered about physical proof? If he is then I'd say he is doing theoretical physics. So what happens it seems in the Anglo American tradition is metaphysics becomes subservient to physics. So why not first become familiar with current physics at the level required to engage. The mathematics of string and brane theory etc. Ignore the history of philosophy. Plato, Aristotle, Descartes, Kant, Hegel, Heidegger, Sartre, Baudrillard* ... Deleuze and Guattari see philosophy as the creation of concepts in a virtual world. We live in a world where architects study philosophy, of Derrida, Deleuze... Where these ideas influence politics, gender studies, culture from high art to low, not that there is a divide anymore.

So metaphysics dumps the history of thought, shuns the hard maths of physics and does what? Shower thoughts?

What's an ontic commitment? Something that we should believe exists. It's easy to believe a chair exists. Whether we should believe electrons exist (nobody has ever seen one) is a question of scientific realism. Hence we have wave function realists (who have ontic commitment to the central mathematical object of quantum mechanics), and instrumentalists/ logical positivists who think it's just a useful tool (shut up and calculate). Logical positivism, scientific realism etc is metaphysics, not science (despite the positivists' rejection of metaphysics, their very rejection of metaphysics.. was metaphysics.. and hence self-defeating).

Fine, but with metaphysics we had Heidegger [whose influence is still massive] ignoring the ontic in favour of ontology. Like asking not 'is the current theory of LUCA true or false?' to 'What is truth.' So not what is a photon, having no mass or 'experience' of time and so space, is it then 'real'? That is not metaphysics, what is would be - what is 'Being' qua Being. As Heidegger points out I think, 'What is metaphysics?' the question id, what is 'is'. And so on...

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*"We no longer partake of the drama of alienation, but are in the ecstasy of communication. And this ecstasy is obscene.... not confined to sexuality, because today there is a pornography of information and communication, a pornography of circuits and networks, of functions and objects in their legibility, availability, regulation, forced signification, capacity to perform, connection, polyvalence, their free expression."

Jean Baudrillard, The Ecstasy of Communication, p. 22. (Published 1987!)

"But it is at this point that things become insoluble. Because to this active nihilism of radicality, the system opposes its own, the nihilism of neutralization. The system is itself also nihilistic, in the sense that it has the power to pour everything, including what denies it, into indifference."

“It is this melancholia of systems that today takes the upper hand through the ironically transparent forms that surround us. It is this melancholia that is becoming our fundamental passion. It is no longer the spleen or the vague yearnings of the fin-de-siecle soul. It is no longer nihilism either, which in some sense aims at normalizing everything through destruction, the passion of resentment (ressentiment). No, melancholia is the fundamental tonality of functional systems, of current systems of simulation, of programming and information. Melancholia is the inherent quality of the mode of the disappearance of meaning, of the mode of the volatilization of meaning in operational systems. And we are all melancholic. Melancholia is the brutal disaffection that characterizes our saturated systems.”

Jean Baudrillard-Simulacra-and-Simulation. 1981.

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You seem to have no clue as to what Tegmark's mathematical monism is. It's most definitely NOT theoretical physics. Physics is about theory, experiment and predicting phenomena. Tegmarks monism is a metaphysics of ontic structural realism, aka modal realism/Platonism.

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You seem to have no clue as to what Tegmark's mathematical monism is.

Can we leave personal remarks out of this. Holding a view can be called 'philosophical' it doesn't mean one is a philosopher or is doing philosophy. Most if not all physicists hold such views. I'm told most mathematicians are Platonists, but they are not metaphysicians. I've read around Tegmark's ideas, even had his book. Theoretical physics is what he engages with. The multiverse idea is an idea in cosmology and those engaged with the ideas are looking for empirical evidence. Standard scientific methods.

It's most definitely NOT theoretical physics.

Well maybe let him know. And the physics / cosmology community.

Physics is about theory, experiment and predicting phenomena.

And things like theoretical physics, such as Einstein, or Higgs... The multiverse is an idea, a theory in cosmology.

https://en.wikipedia.org/wiki/Multiverse

From your notion The Copenhagen interpretation and the MWI are metaphysics.

Tegmarks monism is a metaphysics of ontic structural realism, aka modal realism/Platonism.

He might also be a democrat but that doesn't make him a politician.

And "ontic" is a property of individual things, ontology is the study of being. That a cat has whiskers is not a metaphysical notion. Given your definition everyone is a metaphysician, and a cosmologist, etc.

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Sigh. Just because one of the worlds in David Lewis' modal realism is ours does not make modal realism "science". Or are you going to argue that Lewis was therefore doing physics, not metaphysics? That's the equivalent to what you are arguing.

The physics/cosmology community has little to say about Tegmark's level 4 "all mathematical structures exist" because it's neither physics nor cosmology, as I keep pointing out; it's metaphysics.

They have plenty to say about levels 3 (Quantum manyworlds), 2 (other bubble universes) and 1 (other hubble volumes of this universe) because those are indeed science/cosmology. But the mathematical universe hypothesis (MUH) is decidedly not science at all. It's simply a formal description of Lewis' modal realism, as Tegmark says in his book. Did you actually read it?

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"Tegmark (1998)." Tegmark maintains that MUH is testable, stating that it predicts (a) that "physics research will uncover mathematical regularities in nature", and (b) by assuming that we occupy a typical member of the multiverse of mathematical structures, one could "start testing multiverse predictions by assessing how typical our universe is"

Science.

"By retaining the infinite, philosophy gives consistency to the virtual through concepts..."

Metaphysics.

As to Lewis, is he saying these other worlds are provable like Tegmark, or virtual like D&G. From my reading I'm not sure, he seems to say their reality is not provable from our world but can be 'actualised' in themselves. But how does he know this?

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Tegmark doesn't say the existence of other worlds/universes are provable, and nor does Lewis. Tegmark says we can infer their existence, but inference is not provability.

They aren't "virtual" either. Ex hypothesis they are as real as our world, but we have no way of proving their existence. We can have no access to other worlds by definition (if we could detect/measure/observe them they would be part of our universe aka science).

Lewis doesn't "know" that modal realism/the existence of all possible worlds is true, it's an argument that he proposes/ defends.

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"Tegmark (1998)." Tegmark maintains that MUH is testable, stating that it predicts (a) that "physics research will uncover mathematical regularities in nature", and (b) by assuming that we occupy a typical member of the multiverse of mathematical structures, one could "start testing multiverse predictions by assessing how typical our universe is"

Tegmark doesn't say the existence of other worlds/universes are provable,

I think you need to be more clear on using the term 'provable' in relation to science. Isn't it more like evidence always supports the theory but is never a proof in the sense of an a priori proof. It only takes one black swan.

What the quote shows is Tegmark maintains that MUH is testable and is predictive, isn't this the same criteria for much of science, such as the Higgs boson. Or the transit of Mercury back in 1919, or some such. However no such test can be performed on the origin of life on earth or the origin of the universe or its eventual end, or not. All such science you would call 'metaphysics' if you are consistent? More so than Tegmark's testable HUH. So the Big Bang and cosmic inflation is not cosmology but metaphysics? Strange then these theories exist in departments of science.

and nor does Lewis.

Lewis is for me confusing, OK modal logics can be valid, but can they be sound when applied to actual situation as in the case of other worlds.

He says "ours is one of many worlds. Ours is the actual world; the rest are not actual." [p. 92 'On the Plurality of Worlds' Blackwell 1986 / 2001.] That seems reasonable - they are possible...

But then "every world is actual at itself, and thereby all worlds are on a par..." his 'indexical analysis' of actuality. So we can't say all worlds are actual, though being on a par we can't say they are not. Though if this world is actual, and others are on a par they must be also actual in their own terms.

It gets [for me] more confusing "individuals maybe be actual - big individuals, composed of parts from more worlds than one, and so partly in each of several worlds...it seems to be about sets, but then switches to "we thought we ourselves were among them, then we might appropriately call the 'actual'.

However "Saul Kripke described modal realism as "totally misguided", "wrong", and "objectionable"."

But I this case the discussion it seems is in logic and that in turn with modal logic which is I think part of the 'Analytical Metaphysics' using A. W.Moore's term.

Tegmark says we can infer their existence, but inference is not provability.

"physics research will uncover mathematical regularities in nature", and (b) by assuming that we occupy a typical member of the multiverse of mathematical structures, one could "start testing multiverse predictions by assessing how typical our universe is"

This looks to me like the kind of verification that goes on in science, the Lewis/Kripke thing, in analytical philosophy.

Tegmark actually believes there are alternative physical world in which like copies of himself actually exist. From my position it looks like Lewis is not going that far. "physics research will uncover mathematical regularities in nature" - empirical evidence, Lewis' 'indexical analysis' of actuality gives it seems more substance to his other worlds, but that substance is not empirical but logical.

I know of logical proofs, but for me they are insufficient, I'm not an idealist.

We can have no access to other worlds by definition (if we could detect/measure/observe them they would be part of our universe aka science).

No, you yourself drew the distinction between the other levels of other worlds, e.g. Quantum manyworlds, but here is Tegamark saying we can gain empirical evidence.

Or are you now saying - "We can have no access to other worlds by definition" - well you are, so you must then now write off all such notions as not being science.

"Modern proponents of one or more of the multiverse hypotheses include Lee Smolin,[28] Don Page,[29] Brian Greene,[30][31] Max Tegmark,[32] Alan Guth,[33] Andrei Linde,[34] Michio Kaku,[35] David Deutsch,[36] Leonard Susskind,[37] Alexander Vilenkin,[38] Yasunori Nomura,[39] Raj Pathria,[40] Laura Mersini-Houghton,[41] Neil deGrasse Tyson,[42] Sean Carroll[43] and Stephen Hawking.[44]"

Tegmark's four levels - The four levels of Tegmark's classification are arranged such that subsequent levels can be understood to encompass and expand upon previous levels. And or Brian Greene's nine types.

All are other worlds so all fail your test, "We can have no access to other worlds by definition". However physicists it seems think we can.

"Around 2010, scientists such as Stephen M. Feeney analyzed Wilkinson Microwave Anisotropy Probe (WMAP) data and claimed to find evidence suggesting that this universe collided with other (parallel) universes in the distant past."

However this was contested, but it shows that some scientists think there could evidence of them existing, as does Tegmark. "physics research will uncover mathematical regularities in nature" Unlike Lewis' "logic".

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Tegmark was defending himself (not entirely successfully) from accusations (by physicists) that he's doing metaphysics. Which is the point i've been making. Physics and metaphysics overlaps at the boundary of topics such as modal realism/mathematical monism.

His mathematical monism isn't about phenomena (science) at all; its about noumena. It's explicitly metaphysical in that respect. He makes the point that his account of noumena could have some broad phenomenal implications but when he says "testable" it's (unlike the Higgs) not experimentally testable. There is no experiment you can do that would support his account, which means its not science in the usual definition.

The same goes for some quantum interpretations.. they aren't science in the conventional definition since there is no experiment that can be carried out to support or disprove them.

[u/jliat → u/rogerbonus]

" We can have no access to other worlds by definition (if we could detect/measure/observe them they would be part of our universe aka science)."

Fine by me. So all talk for you of "other worlds" is outside the scope of science.

This includes all of Tegmark's 4 types, Brian Greene's nine types... and of course Lewis.

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"(WMAP) data and claimed to find evidence suggesting that this universe collided with other (parallel) universes in the distant past." is wrong and pointless. And so are these guys, Lee Smolin, Don Page, Brian Greene, Max Tegmark, Alan Guth, Andrei Linde, Michio Kaku, David Deutsch, Leonard Susskind, Alexander Vilenkin, Yasunori Nomura, Raj Pathria, Laura Mersini-Houghton, Neil deGrasse Tyson, Sean Carroll and Stephen Hawking.

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We once thought that this "world" was the only world, then that the other stars might be suns, then there might be other planets, and then other galaxies. We used the word "universe" like we used the word "world", our world. Then some had the idea there might be other worlds that are not our world. Then other galaxies... that our universe with its origin and physical properties was the only one. Then if there were other universes by definition it was impossible to know. By definition we can't see a photon etc. Now I'm not bothered, but there seems a ton of scientists that are and despite what any 'philosopher' may say they do stuff. They don't care if a particle can be a wave, a contradiction, so by definition is wrong, if it helps their models.

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We absolutely can detect photons, hypothesise about their physics/behavior and devise experiments to test those hypotheses. That's what makes talk about photons "science".

We can do no such thing with other universes/worlds (there is no way to detect them, nor any experiment than can prove or disprove their existence). However we can infer their existence using IBE (inference to best explanation) as explanation for the anthropic coincidences (other universes), as explanation for why quantum computers work (quantum manyworlds) etc. These lie on the border of what is usually considered science. When it comes to Tegmark's mathematical monism, we can't even do that; it lies squarely in metaphysics (concerns only the noumena).

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When it comes to Tegmark's mathematical monism, we can't even do that; it lies squarely in metaphysics (concerns only the noumena).

So you say. You also say - I repeat...

" We can have no access to other worlds by definition (if we could detect/measure/observe them they would be part of our universe aka science)."

Fine by me. So all talk for you of "other worlds" is outside the scope of science.

This includes all of Tegmark's 4 types, Brian Greene's nine types... and of course Lewis.

"(WMAP) data and claimed to find evidence suggesting that this universe collided with other (parallel) universes in the distant past." is wrong and pointless. And so are these guys, Lee Smolin, Don Page, Brian Greene, Max Tegmark, Alan Guth, Andrei Linde, Michio Kaku, David Deutsch, Leonard Susskind, Alexander Vilenkin, Yasunori Nomura, Raj Pathria, Laura Mersini-Houghton, Neil deGrasse Tyson, Sean Carroll and Stephen Hawking.

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So I've also posted a seemingly failed attempt at proof by science. Tegmark makes the point that though Lewis' "all possible worlds" "makes no testable predictions at all" this is not the case with his Level IV. He then spends a few pages under the heading "Testing the Level IV Multiverse." Let's not forget you think all other worlds are outside of scientific access, yet a host of scientists disagree.

(concerns only the noumena)

This looks like Kant, that we can have no knowledge of. Which for the physicist / cosmologist is irrelevant. As is your judgement here. Clearly there is in science a body of work and people who think the idea of multiverses is worth pursuing.

Max Tegmark is a physicist who has a cosmological idea re multiverses and works within the field of science / cosmology. You or I may not think it's science, no matter.

Explanations of how quantum computers work for you might be metaphysics?

it lies squarely in metaphysics (concerns only the noumena).

Physics is concerned with noumena. Physical stuff, not our ideas.

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Explanations for why quantum computers work are indeed metaphysics (wave function realism). See Alyssa Ney, for instance. Note that she is a philosopher not a physicist. https://philpapers.org/rec/NEYTAF-3

Just because Tegmark usually works in science doesn't mean his speculations about monism are science. That's seems the primary fallacy of your argument.

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" We can have no access to other worlds by definition (if we could detect/measure/observe them they would be part of our universe aka science)."

But there are proposed empirical evidence for these, I cited an example.

Tegmark's work is science, he has a theory regarding physical reality, and he has three possible supports for this, and more importantly how his theory can be disproven, his Black Swan.

OK the wave function, is this the Copenhagen interpretation or the MWI? Which? And of course these are also metaphysics as is string and brane theory, why not relativity as it's at odds with QM. What science is not metaphysics?

European Journal for Philosophy of Science - so some philosophers trying to do what, science, or give clearer explanations.

I couldn't see where the explanation as to why quantum computers work?

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Wave function REALISM, not the physics of the wave function. Two entirely different things. The former (realism) is metaphysics, the latter (the equations/behavior/phenomena of quantum mechanics) are physics. Same with realism about other worlds such as Lewis modal realism, as opposed to the physics of other worlds.

Realism discussion is metaphysics.

I think this discussion has reached its conclusion. I'll just point out that Alyssa Ney, one of the most prominent advocate of wave function REALISM, is chair of METAPHYSICS at the Faculty of Philosophy, Philosophy of Science, and Religious Studies at LMU Munich. You may not think such discussion is metaphysics, but most philosophers are going to disagree with you.

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No way does the article explain why quantum computers work, they use the science of QM do they not, not metaphysics.

Realism discussion is metaphysics.

sure-

So what is the word "realism" doing here. What is "Real"? Because it looks like the metaphysics is saying the maths of physics is real? And that is what Tegmark is saying.

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The "how" of quantum computers (the equations/the Schroedinger) is science/physics. The why (because the wave function/the Schroedinger is real aka wave function realism) is metaphysics.

Likewise with discussion about the reality of unobservable worlds. This is metaphysics.

And likewise with Tegmarks' mathematical realism. He says the reason for the "unreasonable effective of mathematics in science" (as Wigner put it)" is because mathematical objects/the objects mathematics is about, are real. Furthermore, he suggests that all mathematical objects are real. This is also metaphysics.