Conference 2021: The Nature of Quantum Objects

University of Geneva, November 11-13, 2021

Quantum theory is the most accurate and comprehensive account of matter: no physical theory in the history of science has told us more about the material objects that constitute the world. At the same time, quantum theory is notorious for its puzzling implications about the nature of the objects it purports to describe: particles without definite locations; waves in a space with a dizzying number of dimensions; and correlations between spacelike-separated physical systems.

Philosophical engagement with quantum theory has traditionally focused on solving the quantum measurement problem, the challenge of forging the hugely successful mathematical and empirical apparatus of quantum mechanics into a physical theory––the kind of thing that is capable of explaining quantum phenomena in terms of the behavior of the material constituents of the world. While such investigations have often gone along with the articulation of proposals for the ontology of quantum mechanics, comparatively little attention has been paid to distinctively metaphysical questions about the nature of quantum objects. What are the laws governing the composition of quantum objects? Are fundamental quantum objects metaphysically independent? Are all fundamental properties of quantum objects determinate? What is the nature of locations of quantum objects? How do quantum objects persist?

The goal of this conference is to showcase new work on such questions by bringing together philosophers of physics and metaphysicians pursuing diverse approaches to such questions. We invite contributions on topics including, but not limited to:

  1. Are there quantum objects? Structuralism, Qualitativism, and Haecceitism
  2. What kind of thing is a quantum object? Particles, Fields, and Monism
  3. Are quantum objects metaphysically dependent?
  4. Does quantum theory imply metaphysical indeterminacy in the properties of quantum objects?
  5. Do quantum objects have essential properties?
  6. How do quantum objects relate to space-time? How do quantum objects persist? Do they have locations?
  7. What is the status of material objects in quantum gravity?


All times UTC+1:00 (Geneva time).

Thursday, November 11thFriday, November 12thSaturday, November 13th
09.00-10.15    Tom Pashby TBD  09.30-10.45    Paul M. Näger The mereological problem of entanglement09.00-10.15    Vera Matarese Quantum Fictionalism  
10.30-11.45      Vanessa A. Seifert TBD    11.00-12.15      Elise Crull Existence Monism from bare quantum theory  10.30-11.45      Tomasz Bigaj Are quantum objects individuals? And why should we care?
12.00-13.15      Bryan W. Roberts Matter-Antimatter Exchange as a Spacetime Symmetry   12.00-13.15      Matteo Morganti Quantum Objects and Haecceitism  
14.45-16.00      Alessandro Torza Derivative metaphysical indeterminacy and quantum physics 13.45-15.00      Alastair Wilson Fundamentality and Levels in  Everettian Quantum Mechanics  
16.15-17.30      David A. Glick Determinacy as a Desideratum    15.15-16.30      Gabrielle Kerbel & Nina Emery Configuration Space Realism and Fundamentality  


Tomasz Bigaj: Are quantum objects individuals? And why should we care?

Elise Crull: Existence Monism from bare quantum theory

Recent work in fundamental mereology tends to consider the debate between priority monism and priority pluralism “the only game in town”.  Both views take metaphysical dependence relations (of some kind or other) to be primitive, and both views make important use of quantum physics.  In this talk I shall try to establish a more controversial position: Existence Monism. I do this in two (largely independent) steps: the first is to argue that quantum physics, construed in an interpretation-neutral way, raises serious problems for metaphysical dependence relations as primitive.  This undercuts the “priority’’ qualifier. The second step is to support monism over pluralism by defending it from the significant objections raised in Calosi (2014) and Tallant & Baron (2018).  This defense will again call upon central features of interpretation-neutral quantum theory.   

David Glick: Determinacy as a Desideratum

Some have alleged that quantum theory involves metaphysical indeterminacy. However, this metaphysical claim is underdetermined—there are accounts of quantum theory that posit metaphysical indeterminacy and others that do not. Fortunately, theoretical virtues can help us to resolve this case of underdetermination. Versions of quantum theory that posit metaphysical indeterminacy will be less simple or less informative than their indeterminacy-free counterparts. Moreover, positing metaphysical indeterminacy does not provide a clear gain in explanatory power, contrary to the suggestion of Calosi and Wilson (2021). Thus, determinacy is a desideratum in an interpretation of quantum theory.

Gabrielle Kerbel and Nina Emery: Configuration Space Realism and Fundamentality

Configuration space realism is an account of quantum ontology according to which the wavefunction represents a field in a high-dimensional space. We present a version of configuration space realism that has largely been overlooked in the literature to date and argue that this version should be taken just as seriously as the standard version. Along the way we show how choosing between these different versions of configuration space realism will turn on philosophically nuanced questions about the nature of grounding, the importance of separability and locality, and the role of explanation in metaphysics and physics.

Vera Matarese: Quantum Fictionalism

Are there quantum objects? While representationalists respond in the affirmative, claiming that quantum states directly represent quantum beables, pragmatists and operationalists respond in the negative, the former interpreting quantum states only prescriptively, the latter as just calculation tools.  In this talk, I propose a fictionalist view to account for the nature of quantum objects. The core idea is that quantum objects do not physically exist, and yet they have an explanatory power that underwrites the kind of explanations normally given by representationalists.

Matteo Morganti: Quantum Objects and Haecceitism

In the debate about the metaphysical status of the entities described by non-relativistic quantum mechanics, two arguments are traditionally used in favour of the ‘Received View’ that quantum objects are non-individuals: one having to do with the Identity of the Indiscernibles, the other with quantum statistics and haecceitism. While the former has been the object of intense discussion as of late, the latter has received comparatively little attention. It basically amounts to the following: if quantum objects were individuals, then many-particle systems of ‘indistinguishable particles’ would give rise to haecceitistic differences – i.e., exactly similar physical states that only differ with respect to which particle is which; quantum statistics doesn’t exhibit such haecceitistic differences; hence, quantum objects are not individuals. This argument certainly looks compelling. However, upon scrutiny, it turns out to be less straightforward than it seems. Here, I will reconstruct the argument in detail, and look at ways to steer clear of its conclusion. 

Paul Näger: The mereological problem of entanglement

It is well-known that the entangled quantum state of a composite object cannot be reduced to the states of its parts. This quantum holism provides a peculiar challenge to formulate an appropriate mereological model: When a system is in an entangled state, which objects are there on the micro and macro level, and which of the objects carries which properties? This paper chooses a modeling approach to answer these questions: It proceeds from a systematic overview of consistent mereological models for entangled systems and discusses which of them is compatible with the quantum mechanical evidence (where quantum states are understood realistically). It reveals that entangled quantum systems neither describe undivided wholes nor objects that stand in irreducible relations. The appropriate model assumes that the entangled property is an irreducible non-relational plural property carried collectively by the micro objects, while there is no macro object. In this sense, quantum holism is an instance of property holism, not of object holism.

Tom Pashby: TBD

Bryan Roberts: Matter-Antimatter Exchange as a Spacetime Symmetry

I argue that the correct local spacetime symmetry group is not the Poincaré group, but its universal covering group SL(2,C). Viewing the local existence of a quantum object in spacetime as a representation of a symmetry group, this provides an elegant explanation of the relationship between matter, antimatter, and spacetime: that matter-antimatter exchange is an automorphism of the local spacetime symmetries.

Vanessa Seifert: TBD

Alessandro Torza: Derivative metaphysical indeterminacy and quantum physics 

Alastair Wilson: Fundamentality and Levels in Everettian Quantum Mechanics

Distinctions in fundamentality between different levels of description are central to the viability of contemporary decoherence-based Everettian quantum mechanics (EQM). This approach to quantum theory characteristically combines a precise fundamental reality (one universal wavefunction) with an imprecise emergent reality (multiple decoherent worlds). I explore how the Everettian appeal to fundamentality and emergence fits within extant metaphysical frameworks, identify grounding and concept fundamentality as promising analytical tools, and use them to characterize a system of explanatory levels (with associated laws of nature) for EQM. This Everettian level structure encompasses and extends the ‘classical’ levels structure comprising levels of physics, chemistry, biology, etc., which are recaptured through a correspondence with levels of explanation for the emergent quasi-classical worlds in EQM. There is however a new kind of fundamental level invoked by EQM, a level below any previously recognised classical level; I argue that this level is novel since it is best understood as physically (indeed metaphysically) non-contingent. This result blocks supervenience-based accounts of levels from applying to EQM. Another contrast with classical level structures arises from the irreducibly self-locating element to probabilities in EQM; I argue that the role of self-location gives rise to an additional novel explanatory level within the overall Everettian levels picture.

Funding: Support for travel and accommodation is available for contributors without institutional funding. Please contact the organizers about travel support once your abstract has been accepted.

Attendance: Attendance is free of charge; if you wish to attend the conference and/or join us for dinner, please email:

Organizers: Claudio Calosi, David Schroeren, Maria Nørgaard, Ryan Miller, members of the SNF funded project “The Metaphysics of Quantum Objects” (SNF grant no. 181088, PI Claudio Calosi), Department of Philosophy, University of Geneva, Switzerland.

Contact: Please direct any queries to