Search

Call ‘the realism problem’ the problem of providing realist understandings of quantum theory. Scientific realists usually claim that this problem is settled by solving the measurement problem. Nonetheless, people disagree about which is the best solution. In this paper I argue that the disagreement among certain views can be tracked down to the fact that there are different views about what the realism problem is supposed to be. I distinguish between an adequacy problem, a precision problem (which is the measurement problem), and a completeness problem. I argue that the reason why some people disagree is that they have different realist commitments: ‘relaxed’ realists like proponents of the information-theoretical interpretation of quantum theory, think it is enough to solve the adequacy problem, ‘modest’ realists like wavefunction realists instead believe that there is also a precision problem, while ‘robust’ realists like primitive ontologists insist that quantum theory, even if it solves the precision problem, still needs to be suitably completed. These attitudes are explained by the type of theories one finds satisfactory: while relaxed realists favor principle theories, robust realists prefer constructive theories, and modest realists provide nonconstructive dynamical hybrids as long as they preserve locality and separability. This clarifies why the proponents of the information-theoretical approach endorse standard quantum mechanics with the collapse rule, wavefunction realists favor the many-worlds theory or GRW, and primitive ontologists support the pilot-wave theory.

In this paper, I argue that the many-worlds theory, even if it is arguably the mathematically most straightforward realist reading of quantum formalism, even if it is arguably local and deterministic, is not universally regarded as the best realist quantum theory because it provides a type of explanation that is not universally accepted. Since people disagree about what desiderata a satisfactory physical theory should possess, they also disagree about which explanatory schema one should look for in a theory, and this leads different people to different options.

For scientific realists, quantum mechanics is unsatisfactory because it suffers from the measurement problem. However, there are at least three promising solutions: the pilot-wave theory, the many-worlds theory, and the theory of spontaneous collapse. In this paper I argue that the measurement problem is a false problem for the realist: it was proposed as the last resort to convince the positivists that the theory is not empirically adequate. Instead realists should focus on preserving the reductive explanatory schema that had worked so well in physics before, which requires a theory to have a three-dimensional ontology. Incompleteness argument to this effect have been proposed in the 1920s, but effectively ignored due to the positivistic climate, other unscientific reasons, and theorems which claimed that this project was impossible. When realists re-examined quantum mechanics in the 1950s and later, they happened to focus on the measurement problem. In this paper I speculate on what would have happened if realists instead focused on finding a three-dimensional ontology to complete quantum theory. I show that most paradoxes, puzzles and mysteries connected with quantum mechanics would have never emerge, and that many of what are now considered possible ontological interpretations of the theory would have hardly been taken as viable options.

This paper aims to investigate the so-called paradox of deterministic probabilities: in a deterministic world, all probabilities should be subjective; however, they also seem to play important explanatory and predictive roles which suggest they are objective. The problem is then to understand what these deterministic probabilities are. Recent proposed solutions of this paradox are the Mentaculus vision, the range account of probability, and a version of frequentism based on typicality. All these approaches aim at defining deterministic objective probabilities as to make them compatible with determinism. In this paper I argue that one can think of the equivalent of subjective and objective deterministic probabilities in terms of typicality. Also, I show that only what I identify with objective probabilities play the necessary explanatory and predictive roles, while the subjective components essentially guide beliefs. In this way, the paradox is solved.

The scientific realist wants to read the metaphysical picture of reality through our best fundamental physical theories. The traditional way of doing so is in terms of objects, properties, and laws of nature. For instance, there are families of fundamental particles individuated by their properties of mass and charge, which determine how they move around. One could call this view an object-oriented metaphysics grounded on properties. In this paper, I wish to present an alternative view that one can dub a thin object-oriented metaphysics grounded on structure: there are fundamental entities with no fundamental properties other than the one(s) needed to specify their nature. I argue that my view has several advantages over the received one. In particular, I compare my proposal to the traditional view in the quantum domain and I argue that my view provides a better fit for both approaches to quantum metaphysics, namely the primitive ontology programme and wave-function realism.

Spontaneous localization theories are a class of quantum theories which solve the so-called measurement problem by non-linearly and stochastically modifying the Schrödinger dynamics. In this paper I briefly explain where these theories are coming from, what their driving ideas and main features are, and how they were historically developed. Also, I discuss their empirical and ontological adequacy, as well as their relativistic extensions and their experimental confirmation.

Spontaneous localization theory is a quantum theory proposed by GianCarlo Ghirardi, together with Alberto Rimini and Tullio Weber in 1986. However, soon it became clear to Ghirardi that his work was more than just one theory: he actually developed a framework, a family of theories in which the wavefunction jumps, but where the ontology of the theory is underdetermined. After acknowledging that the wavefunction did not provide a satisfactory ontology, he assumed that matter was described by a continuous matter density field in three-dimensional space, whose evolution is governed by a stochastic wavefunction evolution. Alternatively, Bell assumed that the wavefunction would govern a spatiotemporal event ontology, dubbed ‘flashes.’ However, not much work has been done with the perhaps most obvious possibility, namely that physical objects are made of particles. This paper has two aims. First to explain the reason why people require spontaneous localization theory to be more than just a theory about the wavefunction. This is done by showing how the problem everyone in the foundation of quantum mechanics take to be the fundamental problem of quantum mechanics, namely the measurement problem, is a red herring. Then, the paper explores the possibility of spontaneous localization theories of particles. I argue that this discussion is not a mere exercise, as spontaneous localization theories of particles may be amenable to a relativistic extension which does not require a foliation, and because in general the peculiar type of indeterminism of spontaneous localization theories may help shedding new light on the nature of the tension between quantum theory and relativity.