Muller and Saunders ([2008]) purport to demonstrate that, surprisingly, bosons and fermions are discernible; this article disputes their arguments, then derives a similar conclusion in a more satisfactory fashion. After briefly explicating their proof and indicating how it escapes earlier indiscernibility results, we note that the observables which Muller and Saunders argue discern particles are (i) non-symmetric in the case of bosons and (ii) trivial multiples of the identity in the case of fermions. Both problems undermine the claim that they (...) have shown particles to be physically discernible. We then prove two results concerning observables that are truly physical: one showing when particles are discernible and one showing when they are not (categorically) discernible. Along the way we clarify some frequently misunderstood issues concerning the interpretation of quantum observables. 1 Background2 Criticisms2.1 Bosons2.2 Fermions3 Reformulating the Insight3.1 What weakly discerns?3.2 General results4 Conclusion. (shrink)

The Hole Argument was originally formulated by Einstein and it haunted him as he struggled to understand the meaning of spacetime coordinates in the context of the diffeomorphism invariance of general relativity. This argument has since been put to philosophical use by Earman and Norton to argue against a substantival conception of spacetime. In the present work I demonstrate how Earman and Norton’s Hole Argument can be extended to exclude everything and not merely substantival manifolds. These casualties of the hole (...) demonstrate that the Hole Argument hinges essentially on our notion of determinism and not on the diffeomorphic freedom of general relativity. Just as Earman and Norton argue that we should not let our metaphysics run roughshod over the structure of our physical theories, so I will argue that, in particular, we should not uncritically allow our metaphysics to dictate what our physical theories must determine. The central conviction which drives the arguments of this paper is that deterministic theories are not required to determine for future moments what they cannot determine for any present or past moments. I provide two arguments to the effect that a physically informed notion of determinism does not require general relativity to determine substantival facts. Consequently the Hole Argument cannot be used against substantival spacetime. The position that I advocate is an instance of “sophisticated determinism.”. (shrink)

Some authors have attempted to defend Leibniz’s Identity of Indiscernibles through weak discernibility. The idea is that if there is a symmetric, nonreflexive physical relation that holds between two particles, then those particles cannot be identical. In this article I focus only on Muller and Saunders’s account and argue that the means by which they achieve weak discernibility is not through a quantum mechanical observable but an alternate mathematical construction that is both unorthodox and incomplete.

In this paper, I will argue that metaphysicians ought to utilize quantum theories of gravity as incubators for a future metaphysics. I will argue why this ought to be done and will present cases studies from the history of science where physical theories have challenged both the dogmatic and speculative metaphysician. I provide two theories of QG and demonstrate the challenge they pose to certain aspects of our current metaphysics; in particular, how they challenge our understanding of the abstract–concrete distinction. (...) I demonstrate how five different accounts of the distinction each fail to hold under the received interpretations of loop quantum gravity and string theory. The central goal of this paper is to encourage metaphysicians to look to physical theories, especially those involving cosmology such as string theory and loop quantum gravity, when doing metaphysics. (shrink)

In this paper, I will argue that metaphysicians ought to utilize quantum theories of gravity as incubators for a future metaphysics. In §1, I will argue why this ought to be done. In §2, I will present case studies from the history of science where physical theories have challenged both the dogmatic and speculative metaphysician. In §3, I will present two theories of QG and demonstrate the challenge they pose to certain aspects of our current metaphysics; in particular, how they (...) challenge our understanding of the abstract-concrete distinction. In this section I demonstrate how five different accounts of the distinction each fail to hold under the received interpretations of loop quantum gravity and string theory. The central goal of this paper is to encourage metaphysicians to look to physical theories, especially those involving cosmology such as string theory and loop quantum gravity, when doing metaphysics. (shrink)

A popular-level discussion of the mutual significance of physics and philosophy over the ages.

The ontological issues at stake given the theory of loop quantum gravity include the status of spacetime, the nature and reality of spin-networks, the relationship of classical spacetime to issues of causation and the status of the abstract-concrete distinction. I this paper I argue that, while spacetime seems to disappear, the spirit of substantival spacetime lives on under certain interpretations of the theory. Moreover, in order for there to be physical spin-networks, and not merely mathematical artifacts, I argue that we (...) must interpret the theory as including a substantival background manifold. This latter result is important for any project which interprets spacetime as an emergent structure from physical spin-networks. (shrink)

It is argued that certain quantum theories of gravity — string theory, loop quantum gravity, non-commutative field theory — do not include spacetime as part of their fundamental ontology. There is a concern in the literature that theories of this kind are physically opaque and empirically incoherent. In this paper, I clarify and amend Huggett and Wüthrich’s argument against these claims. Whereas the content of this paper centres on the disappearance and re-emergence of spacetime in quantum gravity, much of the (...) philosophical work centres more generally on issues of (emergent) ontology and how this ontology can be extracted from formal theories, the role of formal derivations in justifying ontological relations, the nature of Kuhnian revolutions, and the application of these revolutions to quantum gravity. (shrink)

Theoria, Volume 88, Issue 4, Page 727-732, August 2022.