Allori,Valia, and . On the metaphysics of quantum mechanics

2013, In Soazig Lebihan (ed.), Precis de la Philosophie de la Physique, Vuibert.

Abstract: Many solutions have been proposed for solving the problem of macroscopic superpositions of wave function ontology. A possible solution is to assume that, while the wave function provides the complete description of the system, its temporal evolution is not given by the Schroedinger equation. The usual Schroedinger evolution is interrupted by random and sudden “collapses”. The most promising theory of this kind is the GRW theory, named after the scientists that developed it: Gian Carlo Ghirardi, Alberto Rimini and Tullio Weber. It seems tempting to think that in GRW we can take the wave function ontologically seriously and avoid the problem of macroscopic superpositions just allowing for quantum jumps. In this paper it is argued that such “bare” wave function ontology is not possible, neither for GRW nor for any other quantum theory: quantum mechanics cannot be about the wave function simpliciter. All quantum theories should be regarded as theories in which physical objects are constituted by a primitive ontology. The primitive ontology is mathematically represented in the theory by a mathematical entity in three-dimensional space, or space-time.

Comment: This is a very interesting article on the ontology of Quantum Mechanics. It is recommended for advanced courses in Philosophy of Science, especially for modules in the Philosophy of physics. Previous knowledge of Bohmian mechanics and the Many Words Interpretation is necessary. Recommended for postgraduate students.

Brading, Katherine, and Castellani, Elena. Symmetry and Symmetry Breaking

2013, The Standford Encyclopedia of Philosophy

Introduction: Symmetry considerations dominate modern fundamental physics, both in quantum theory and in relativity. Philosophers are now beginning to devote increasing attention to such issues as the significance of gauge symmetry, quantum particle identity in the light of permutation symmetry, how to make sense of parity violation, the role of symmetry breaking, the empirical status of symmetry principles, and so forth. These issues relate directly to traditional problems in the philosophy of science, including the status of the laws of nature, the relationships between mathematics, physical theory, and the world, and the extent to which mathematics suggests new physics.

This entry begins with a brief description of the historical roots and emergence of the concept of symmetry that is at work in modern science. It then turns to the application of this concept to physics, distinguishing between two different uses of symmetry: symmetry principles versus symmetry arguments. It mentions the different varieties of physical symmetries, outlining the ways in which they were introduced into physics. Then, stepping back from the details of the various symmetries, it makes some remarks of a general nature concerning the status and significance of symmetries in physics.

Comment: This article offers a good introduction to the topic of symmetries. The entry begins with a brief description of the historical roots and emergence of the concept of symmetry that could serve as a reading for undergraduates. It then turns to the application of this concept to physics and merges the discussion with issues in relativity and quantum mechanics. This second part of the article is thus more suitable to postgraduate courses in philosophy of science, specially, philosophy of physics. It could serve as a secondary reading for those researching the laws of nature.

Cartwright, Nancy, and . How the Laws of Physics Lie

1983, Oxford University Press.

Publisher’s Note: Nancy Cartwright argues for a novel conception of the role of fundamental scientific laws in modern natural science. If we attend closely to the manner in which theoretical laws figure in the practice of science, we see that despite their great explanatory power these laws do not describe reality. Instead, fundamental laws describe highly idealized objects in models. Thus, the correct account of explanation in science is not the traditional covering law view, but the ‘simulacrum’ account. On this view, explanation is a matter of constructing a model that may employ, but need not be consistent with, a theoretical framework, in which phenomenological laws that are true of the empirical case in question can be derived. Anti?realism about theoretical laws does not, however, commit one to anti?realism about theoretical entities. Belief in theoretical entities can be grounded in well?tested localized causal claims about concrete physical processes, sometimes now called ‘entity realism’. Such causal claims provide the basis for partial realism and they are ineliminable from the practice of explanation and intervention in nature.

Comment: Essential reading on realism and anti-realism about the laws of nature. Recommended for undergraduates who have prior knowledge of Humeanism about laws and for postgraduates in general. The book consists of a series of philosophical essays that can be used independently.

Ismael, Jenann, and . Quantum Mechanics

2014, The Standford Encyclopedia of Philosophy

Introduction: Quantum mechanics is, at least at first glance and at least in part, a mathematical machine for predicting the behaviors of microscopic particles – or, at least, of the measuring instruments we use to explore those behaviors – and in that capacity, it is spectacularly successful: in terms of power and precision, head and shoulders above any theory we have ever had. Mathematically, the theory is well understood; we know what its parts are, how they are put together, and why, in the mechanical sense (i.e., in a sense that can be answered by describing the internal grinding of gear against gear), the whole thing performs the way it does, how the information that gets fed in at one end is converted into what comes out the other. The question of what kind of a world it describes, however, is controversial; there is very little agreement, among physicists and among philosophers, about what the world is like according to quantum mechanics. Minimally interpreted, the theory describes a set of facts about the way the microscopic world impinges on the macroscopic one, how it affects our measuring instruments, described in everyday language or the language of classical mechanics. Disagreement centers on the question of what a microscopic world, which affects our apparatuses in the prescribed manner, is, or even could be, like intrinsically; or how those apparatuses could themselves be built out of microscopic parts of the sort the theory describes.

Comment: The paper does not deal with the problem of the interpretation of quantum mechanics, but with the mathematical heart of the theory; the theory in its capacity as a mathematical machine. It is recommendable to read this paper before starting to read anything about the interpretations of the theory. The explanation is very clear and introductory and could serve as an introductory reading for both undergraduate and postgraduate courses in philosophy of science focused on the topic of quantum mechanics. Though clearly written, there is enough mathematics here to potentially put off symbol-phobes.

Kleinsschmidt, Shieva, and . Reasoning without the principle of sufficient reason

2013, In Tyron Goldschmidt (ed.), The Philosophy of Existence: Why Is There Something Rather Than Nothing? Routledge. 64-79.

Abstract: According to Principles of Sufficient Reason, every truth (in some relevant group) has an explanation. One of the most popular defenses of Principles of Sufficient Reason has been the presupposition of reason defense, which takes endorsement of the defended PSR to play a crucial role in our theory selection. According to recent presentations of this defense, our method of theory selection often depends on the assumption that, if a given proposition is true, then it has an explanation, and this will only be justified if we think this holds for all propositions in the relevant group. In this paper the author argues that this argument fails even when restricted to contingent propositions, and even if we grant that there is no non-arbitrary way to divide true propositions that have explanations from those that lack them. The author gives an alternate explanation of what justifies our selecting theories on the basis of explanatory features: the crucial role is not played by an endorsement of a PSR, but rather by our belief that, prima facie, we should prefer theories that exemplify explanatory power to greater degrees than their rivals.

Comment: The text covers many topics in a level proper for undergraduates: The principle of sufficient reason, the inductive argument, the problem of the Many, explanatory power, etc. Even if the reader doesn't identify with the view of the author, this article could serve as a good practice to build confidence with philosophical concepts that are crucial for metaphysics and philosophy of science.

Massimi, Michela, and John Peacock. The origins of the universe: laws, testability and observability in cosmology

2014, in M. Massimi (ed.), Philosophy and the Sciences for Everyone. Routledge.

Summary: How did our universe form and evolve? Was there really a Big Bang, and what came before it? This chapter takes the reader through the history of contemporary cosmology and looks at how scientists arrived at the current understanding of our universe. It explores the history of astronomy, with the nebular hypothesis back in the eighteenth century, and in more recent times, Einstein’s general relativity and the ensuing cosmological models. Finally, it explains the current Standard Model and early universe cosmology as well as the experimental evidence behind it.

Comment: This chapter could be used as an introductory reading to philosophy of cosmology. It provides a general overview of the history of cosmology and of the philosophical problems (laws, uniqueness, observability) that stood in the way of cosmology becoming a science. It is recommendable for undergraduate courses.

Massimi, Michela, and John Peacock. What are dark matter and dark energy?

2014, in M. Massimi (ed.), Philosophy and the Sciences for Everyone. Routledge

Summary: According to the currently accepted model in cosmology, our universe is made up of 5% of ordinary matter, 25% cold dark matter, and 70% dark energy. But what kind of entities are dark matter and dark energy? This chapter asks what the evidence for these entities is and which rival theories are currently available. This provides with an opportunity to explore a well-known philosophical problem known as under-determination of theory by evidence.

Comment: This Chapter could serve as an introduction to contemporary cosmology and particle physics or as an example to illustrate the problem of under-determination of theory by evidence. The chapter looks at alternative theories that explain the same experimental evidence without recourse to the hypothesis of dark matter and dark energy and discusses the rationale for choosing between rival research programs. Like the rest of the chapters in this book, it is a reading recommendable for undergraduate students. It is recommended to read it after Chapter 2 of the same book.

Morrison, Margaret, and . Spin: All is not what it seems

2007, Studies in History and Philosophy of Science Part B 38(3): 529-55.

Abstract: Spin is typically thought to be a fundamental property of the electron and other elementary particles. Although it is defined as an internal angular momentum much of our understanding of it is bound up with the mathematics of group theory. This paper traces the development of the concept of spin paying particular attention to the way that quantum mechanics has influenced its interpretation in both theoretical and experimental contexts. The received view is that electron spin was discovered experimentally by Stern and Gerlach in 1921, 5 years prior to its theoretical formulation by Goudsmit and Uhlenbeck. However, neither Goudsmit nor Uhlenbeck, nor any others involved in the debate about spin cited the Stern-Gerlach experiment as corroborating evidence. In fact, Bohr and Pauli were emphatic that the spin of a single electron could not be measured in classical experiments. In recent years experiments designed to refute the Bohr-Pauli thesis and measure electron spin have been carried out. However, a number of ambiguities surround these results – ambiguities that relate not only to the measurements themselves but to the interpretation of the experiments. After discussing these various issues the author raises some philosophical questions about the ontological and epistemic status of spin.

Comment: The goal of the paper is to uncover and isolate how spin presents problems for traditional realism and to illustrate the power that theories like quantum mechanics have for shaping both philosophical questions and answers. It is adequate for higher-level postgraduate courses in Philosophy of Science.

Ruetsche,Laura, and . Interpreting Quantum Theories: The art of the possible

2011, Oxford University Press.

Publisher’s Note: Traditionally, philosophers of quantum mechanics have addressed exceedingly simple systems: a pair of electrons in an entangled state, or an atom and a cat in Dr. Schrodinger’s diabolical device. But recently, much more complicated systems, such as quantum fields and the infinite systems at the thermodynamic limit of quantum statistical mechanics, have attracted, and repaid, philosophical attention. Interpreting Quantum Theories has three entangled aims. The first is to guide those familiar with the philosophy of ordinary QM into the philosophy of ‘QM infinity’, by presenting accessible introductions to relevant technical notions and the foundational questions they frame. The second aim is to develop and defend answers to some of those questions. Does quantum field theory demand or deserve a particle ontology? How (if at all) are different states of broken symmetry different? And what is the proper role of idealizations in working physics? The third aim is to highlight ties between the foundational investigation of QM infinity and philosophy more broadly construed, in particular by using the interpretive problems discussed to motivate new ways to think about the nature of physical possibility and the problem of scientific realism.

Comment: Really interesting book for postgraduate courses involving the study of interpretative theories of Quantum Mechanics. The argument is focused on the quantum theory of systems with infinitely many degrees of freedom. The philosophical approach is defended through careful attention to scientific details.

Spencer, Quayshawn, and . Do Newton’s Rules of Reasoning Guarantee Truth … Must They?

2004, Studies in History and Philosophy of Science 35(4): 759-782.

Abstract: Newton’s Principia introduces four rules of reasoning for natural philosophy. Although useful, there is a concern about whether Newton’s rules guarantee truth. After redirecting the discussion from truth to validity, I show that these rules are valid insofar as they fulfill Goodman’s criteria for inductive rules and Newton’s own methodological program of experimental philosophy; provided that cross-checks are used prior to applications of rule 4 and immediately after applications of rule 2 the following activities are pursued: (1) research addressing observations that systematically deviate from theoretical idealizations and (2) applications of theory that safeguard ongoing research from proceeding down a garden path.

Comment: A good examination of the relationship of scientific practices to truth, put in a historical context. Would be useful in a history and philosophy of science course.