In the recent philosophical literature, several counterexamples to the interpretative principle that symmetry-related models are physically equivalent have been suggested The Oxford handbook of philosophy of physics, Oxford University Press, Oxford, 2013, Noûs 52:946–981, 2018; Fletcher in Found Phys 50:228–249, 2020). Arguments based on these counterexamples can be understood as arguments from scientific practice of roughly the following form: because in scientific practice such-and-such symmetry-related models are treated as representing distinct physical situations, these models indeed represent distinct physical situations. In (...) this paper, a strategy for analysing arguments of this type is presented and applied to the examples that can be found in the literature. I argue that if we are exclusively interested in models understood as representing entire possible worlds, arguments from scientific practice should involve some additional assumptions to guarantee they are relevant for models understood in this way. However, none of the examples presented in the literature satisfy all these additional assumptions, which leads to the conclusion that arguments from scientific practice based on these examples do not undermine the interpretative principle that different symmetry-related models represent the same possible world. (shrink)

Absolute velocities in Newtonian mechanics are commonly regarded as unmeasurable. Roberts (Br J Philos Sci 59(2):143–168, 2008) provides a justification for this thesis which appeals to the observational indistinguishability of boost-related models of Newtonian mechanics. Middleton and Murgueitio Ramírez (Australas J Philos, 2020) criticise his argumentation by pointing out that his analysis of the notion of measurement is too restrictive, and that, under a weaker analysis (based on counterfactuals), absolute velocities are measurable. Jacobs (Australas J Philos, 2020) opposes their view, (...) arguing that, on a properly formulated counterfactual-based account of measurement, absolute velocities are unmeasurable. However, in his argument, observational indistinguishability plays no role, even though, intuitively, it is very relevant for the issue of (un)measurability. This paper’s aim is to bring observational indistinguishability back to this discussion. I build upon the observation that there is an analogy between possible views on knowledge and justification on the one hand, and on measurement on the other. In particular, I explore the distinction between externalist and internalist approaches. Counterfactual-based accounts are all externalist, whereas the observational indistinguishability of boost-related models becomes relevant if we are interested in an internalist concept of measurement. (shrink)

The article investigates the relations between Hausdorff and non-Hausdorff manifolds as objects of general relativity. We show that every non-Hausdorff manifold can be seen as a result of gluing together some Hausdorff manifolds. In the light of this result, we investigate a modal interpretation of a non-Hausdorff differential manifold, according to which it represents a bundle of alternative space-times, all of which are compatible with a given initial data set.

In this paper non-Hausdorff manifolds as potential basic objects of General Relativity are investigated. One can distinguish four stages of identifying an appropriate mathematical structure to describe physical systems: kinematic, dynamical, physical reasonability, and empirical. The thesis of this paper is that in the context of General Relativity, non-Hausdorff manifolds pass the first two stages, as they enable one to define the basic notions of differential geometry needed to pose the problem of the evolution-distribution of matter and are not in (...) conflict with the Einstein equations. With regard to the third stage, various potential conflicts with physical reasonability conditions are considered with a tentative conclusion that non-Hausdorff manifolds are more likely to pass this stage than is typically assumed. When dealing with some of these problems, the modal interpretation of non-Hausdorff manifolds is invoked, according to which they represent bundles of alternative possible spacetimes rather than single spacetimes. (shrink)

In this paper, I argue that the Hole Argument can be formulated without using the notion of isomorphism, and for this reason it is not threatened by the criticism of Halvorson and Manchak (Br J Philos Sci, 2022. https://doi.org/10.1086/719193). Following Earman and Norton (Br J Philos Sci 38, pp. 515–525, 1987), I divide the Hole Argument into two steps: the proof of the Gauge Theorem and the transition from the Gauge Theorem to the conclusion of radical indeterminism. In the analaysis (...) of the first step, I argue that the Gauge Theorem does not rely on the notion of isomorphism but on the notion of the diffeomorphism-invariance of the equations of local spacetime theories; however, for this approach to work, the definition of local spacetime theories needs certain amendments with respect to Earman and Norton’s formulation. In the analysis of the second step, I postulate that we should use the notion of radical indeterminism instead of indeterminism simpliciter and that we should not decide in advance what kind of maps are to be used in comparing models. Instead, we can tentatively choose some kind of maps for this purpose and check whether a given choice leads to radical indeterminism involving empirically indistinguishable models. In this way, the use of the notion of isomorphism is also avoided in the second step of the Hole Argument. A general picture is that physical equivalence can be established by means of an iterative procedure in which we examine various candidate classes of maps, and, depending on the outcomes, we need to broaden or narrow these classes. The Hole Argument can be viewed as a particular instance of this procedure. (shrink)

In this paper, it is argued that, contrary to some suggestions in the philosophical literature, dispositions cannot replace laws in the description of the physical world. If for a certain type of physical situation a well-working law-based account is available, then it is not possible to describe that situation equally well in terms of dispositions. Using an example consisting of four laws (Coulomb’s law, Newton’s law of gravitation, the rule for the composition of forces and Newton’s second law), it is (...) shown that when one attempts to replace a law-based account with a disposition-based account, the latter turns out to be either less informative or inferior with respect to theoretical virtues, such as simplicity, unification, non-triviality of predictions and explanatory power. Laws are also better suited to deal with interactions and their screening off. Using inference to the best explanation, one can conclude from this comparison that it is laws rather than dispositions that should be included in our ontological picture of nature. (shrink)

In the recent philosophical debate about the relationship between symmetries and physical equivalence, two approaches have been distinguished: motivationalism and interpretationalism. In this paper, I point out that there are variants of interpretationalism that have not been taken into account by the proponents of motivationalism. I also argue that some of these overlooked variants of interpretationalism are not prone to the motivationalists’ criticism and overall are the most attractive positions available.

In this paper, I challenge the distinction between “epistemic” and “ontic” states propounded by Harrigan and Spekkens (Found Phys 40:125–157, 2010) by pointing out that because knowledge is factive, any state that represents someone’s knowledge about a physical system thereby also represents something about the physical system itself, so there is no such thing as “mere knowledge”. This criticism leads to the reformulation of the main question of the debate: instead of asking whether a given state is ontic or epistemic, (...) we should instead ask whether a given change of a state is ontic or epistemic. In particular, in the context of quantum mechanics, one can ask whether the collapse of the quantum state could be understood as an epistemically successful change of the observer’s beliefs about the complete state of the system that is not associated with any change in the physical reality. I argue that the answer to this question should be in the negative because it is possible that, in a series of measurements, the collapse rule tells us to update a certain state to a different one and then back to the same state; if both of these updates are merely changes of our beliefs, then they could not both be epistemically successful. (shrink)

This paper investigates various properties that may by possessed by quantum states, which are believed to be specifically “quantum” and their opposites. It also considers their “absolute” counterparts in the following sense: a given state has a given property absolutely if after an arbitrary unitary transformation it still possesses it. The known relations between the listed properties and between their absolute counterparts are summarized. It is proven that the only two-qubit state that has zero quantum discord absolutely is the maximally (...) mixed state. Finally, related conceptual issues concerning the terms “classical” and “quantum” are discussed. (shrink)

One of the modern approaches to the laws of nature regards them as relations between universals. The most advanced version of such an approach has been presented by D. M. Armstrong. The aim of this paper is to reconstruct and interpret Armstrong’s conception but also to evaluate his theory and to point out what expectations from it are inadequate. My point of reference are two objections to Armstrong’s ideas, namely the problems of identification and inference. I claim that Armstrong’s theory (...) in general and his response to both problems in particular are based on some fundamental metaphysical principles, namely: the principle of identity for universals, the principle of non-contradiction, the relational principle of the indiscernibility of identicals and the principle of contingent necessity. The central part of my interpretation shows how from the laws of nature, properly understood, the occurrence of some states of affairs necessarily results provided that these principles are employed. (shrink)