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How can physics, particularly Quantum Field Theory (QFT), contribute to clarifying the ontological nature of objects, in light of different mereological positions such as mereological nihilism, mereological universalism, deflationism, and ordinary object realism?

In particular, how can QFT help us understand the relationship between the properties of fundamental particles and the properties of the objects they compose, and whether there is a "ladder" of ontological fundamentality between objects?

Here are some links to resources that led me to this question:

Do Chairs Exist?, Youtube video from the Vsauce channel.

Comment about electron delocalisation in Electrons and atoms discussion on Physics Stackexchange.

Does a QFT world mean object A becomes object B instead of obj. A moving? Quora Q&A thread.

Julius Hamilton
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Marco Fabbri
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  • I don't think it can help you understand the ladder of fundamentality, it's just another layer on that ladder (or rung? I guess) – TKoL Mar 15 '24 at 14:33
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    You might like this answer to the question: 'Is the idea that "Everything is energy" even coherent?' https://philosophy.stackexchange.com/questions/85899/is-the-idea-that-everything-is-energy-even-coherent/85950#85950 I'd argue that behaviour that only shows up in very rarified high-energy environments like particle colliders, isn't so much more fundamental, as that it provides bridges between domains, like a view into the early universe when we think such small scale forces dominated & much of cosmic structure was determined, & high energy small scale phenomena where all 4 forces are relevant – CriglCragl Mar 15 '24 at 15:46
  • Mereology is akin to logic and mathematics. QFT is compatible with a wide range of mereologies, and can no more help us with sorting out parts and wholes than with deciding whether the axiom of choice is true or large cardinals exist. Those are ultimately judged pragmatically, on the totality of their applications, not on any particular physical theory. But there is some work on "quantum mereology" that services quantum objects specifically, see Holik-Jorge's survey. – Conifold Mar 16 '24 at 01:35

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CriglCragl is correct; you and I can live out our lives on earth with no knowledge or understanding of QFT at all and suffer no philosophical consequences whatever. QFT is important at time and energy scales which are completely outside of normal human experience and for the purposes of philosophy can be safely ignored.

Note also that QFT is a strict mathematical formalism used by specialists to furnish predictive results when running physics experiments. It takes years of post-doctorial effort to master the field. Anyone wishing to contribute substantively to that field must as a prerequisite be fluent in the mathematical language used in it. This does not disqualify philosophers from having opinions about QFT but absent that prerequisite, it means those opinions don't matter.

niels nielsen
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  • Although you make a good point, I think you are overstating it. Physicists working in QM have made philosophical claims based on QM, and the opinions of philosophers about those philosophical points are at least as substantive as those of the physicists--I'd argue more, since the philosophers have a lot more background to know what doesn't work philosophically. – David Gudeman Mar 15 '24 at 18:49
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    I would like to read those philosophical claims. Can you steer me to a source? -NN – niels nielsen Mar 15 '24 at 18:51
  • @NielsNielsen I agree with most part of your answer. Alone, I cannot follow your disesteem of the relevance of QFT. For understanding the interaction of electrons and photons like in QED and also for the philosophical consequences of emphasizing the field concept in explaining nature. – Jo Wehler Mar 15 '24 at 19:14
  • There is so much, I wouldn't know where to start. I suggest doing a search for "quantum mechanics philosophy". – David Gudeman Mar 15 '24 at 20:53
  • @JoWehler, no disesteem intended. I only wanted to make the point that QFD isn't a philosophy topic. – niels nielsen Mar 15 '24 at 22:01
  • "This does not disqualify [set of persons] from having opinions about [idea] but absent that prerequisite, it means those opinions don't matter." Haw haw haw! I wish I could say that to just about everyone, about just about everything! Well put. – Scott Rowe Mar 15 '24 at 23:14
  • But, bridges between domains are philosophically important, as is understanding cosmic structure. General Relativity used to be portrayed like you do QFT, but now people literally study it at high school. Knowledge becomes more digestible & integrated over time. My point was along the lines of the claim that 'everything is energy' is misunderstood as an ontological claim, when I see it more it more as a statement that energy is a language capable of describing many phenomena (but not eg entropy) – CriglCragl Mar 16 '24 at 00:43
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    @ScottRowe, thank you for that, I think. – niels nielsen Mar 16 '24 at 04:34
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  1. Quantum field theory (QFT) is a good opportunity to rethink and check mereological viewpoints like “The part and the whole”. A basic insight from QFT states that the number of particles during an experiment or also spontaneously can change.

    Historically, one of the first examples is the radioactive decay of heavy atoms. A phenomenon observed in the scientific context since more than 100 years, and some decades before the development of QFT.

    A typical examples from QFT is the annihilation of a particle and its antiparticle into a burst of photons. A basic requirement of the theory is to deal with changing particle numbers, and to ask which physical property are conserved even when the particle number changes.

  2. I do not see a close collaboration between physicists working in QFT and philosophers working in mereology. A collaboration to find a common view onto physical processes in microphysics with changing particle numbers.

    QFT emphasizes the viewpoint that thinking in conservation theorems for processes with changing particle numbers is more fruitful than thinking in static compositions of a whole into parts.

    I am sceptical about philosophical approaches which just carry over concepts from everyday world and apply them to the unknown microworld. A standard example is to invoke and to argue with the philosophical “chair” or “table”. Your first link leaves me a bit confused.

Jo Wehler
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    The idea that objects can change goes back to at least 600 BC (see the Sorites Paradox, the Ship of Theseus, and various writings on Classical atomism). I don't see that quantum mechanics has added anything to the already well-known problems of object and parthood. I think it's the other way around: quantum mechanics is physicists finally realizing that atomism doesn't solve the problems that were raised two and a half millennia ago. – David Gudeman Mar 15 '24 at 18:46
  • @DavidGudeman Please note the OP's question is about "particularly Quantum Field Theory", not about quantum theory in the general. – Jo Wehler Mar 15 '24 at 18:51
  • A particle-antiparticle collision will produce 1 photon (see Feynman diagrams), though being high energy if that hits anything it will produce a particle cascade, like cosmic rays do. – CriglCragl Mar 16 '24 at 00:50
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I am not sympathetic to mereological nihilism or universalism, since both, to me, appear empty wordplay with nothing helpful to say. Indeed, I recommend that mereology should be hyphenated. However, I offer the following observations...

QFT seems to offer a challenge to MN in the sense that particles with mass, such as electrons and positrons, can be created or destroyed, replacing, or being replaced by photons. You can't say that an electron and a positron are an arrangement of a photon any more than you can say that a photon is an arrangement of an electron and a positron, so neither can be the simple to the other. At the very least you have to consider two types of simples each of which can disappear and be replaced by the other in the right circumstances. Perhaps the MN fans have a version of their idea that is compatible with that- I wouldn't know.

QFT and quantum mechanics generally are notoriously a mess ontologically speaking, with endless arguments about what is a particle, what is a field and so on (even between physicists, so it gets worse when philosophers start on it). The best you can say is that if you model microscopic systems using wave functions in QM and fields in QFT you can get results that agree with experiments, if you scatter electrons, say, from other particles, they always seem to be tiny point-like things with no structure, and they seem real enough when you get gazillions of them in aggregate, as is the case when you consider a collections of particles forming four legs a seat and a back, aka a chair.

Marco Ocram
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