In 2021, our Department of Philosophy admitted a PhD cohort composed entirely of nonbinary students. As that cohort, we offer our experiences as a case study, with two aims. First, we investigate and provide examples of the particular kinds of epistemic injustice perpetrated against nonbinary philosophers, and second, we highlight one antidote to this epistemic injustice: communities of epistemic sanctuary. Toward these ends, we offer narrative accounts of three distinct experiences over our first year as PhD students. We discuss how our nonbinary community of three provided insulation against the alienation nonbinary philosophers face in academia. Furthermore, this insulation had a distinctly epistemic hue. Therefore, we argue that developing communities of epistemic sanctuary combats the epistemic injustice that disenfranchises trans thinkers in our field.

Since it neither relies on a collapse postulate, nor posits a hidden variable, Everettian quantum mechanics (EQM) has emerged as an attractive option among the various realist interpretations of quantum mechanics. In this sense, EQM is a simpler theory than its competitors. However, it appears to be quite a bit more complex, ontologically speaking; unlike its competitor theories, EQM has been taken to entail a plethora of worlds. This paper concerns perhaps the most prominent metaphysical objection raised against EQM: that of ontological extravagance. 

Everettians have given this objection little serious attention. For instance, Wallace (2012) dismisses this objection as relying on a misinterpretation of Ockham’s razor. Where Ockham’s razor merely concerns the economy of postulates and the overall intricacy of our body of theory, Wallace insists that his skeptic instead appeals to a new criterion, under which we ought to minimize the size of the universe that our theory posits. Contra Wallace, I argue that the objection does not rest on a misinterpretation of Ockham’s razor, but on a different scientific norm altogether: the minimum divergence norm, as advocated by Emery (2017, 2023). 

According to the minimal divergence norm (MDN), we ought to prefer theories that deviate least from the manifest image, or the way we generally perceive the world to be. For any pair of equally empirically adequate and explanatorily useful theories, then, we ought to prefer the theory that posits the physical reality most closely aligned with our perception of physical reality. Here I diverge from Emery; it is a step too far to assert that there is some image of the world that is the manifest image. After all, observations themselves depend on our theoretical commitments. While EQM does not necessarily posit that the world itself is vastly different from how it appears, it is generally taken to entail many more worlds than its competitor theories. The heart of the objection is this: EQM demands an over-abundance of concreta beyond what we perceive when we look at the world; indeed, for each concrete object we observe, EQM is taken to entail many more such objects, each in a distinct world. On this metaphysical view of EQM, then, that which there is vastly diverges from what we observe, in a dramatic departure from the manifest image. Assuming that we ought to endorse the MDN, this objection poses a serious issue for Everettians committed to a many worlds ontology. 

In this paper, I first present a stronger version of this objection than has been previously articulated. Second, I use this objection to evaluate the most prominent competitor ontologies of EQM, demonstrating that it condemns only those approaches that involve many worlds.

Bare Everettian quantum mechanics (EQM) suggests that for any quantum mechanical process, all possible outcomes obtain. On first inspection, EQM appears to lend itself well to many worlds interpretations. However,  this approach requires the metaphysical commitment to a form of modal realism. In response to this concern, I propose a single-world Everettian universe. On my model, the complete branching structure itself is a metaphysically possible world. To solve the problem of identity in a single world where all possible outcomes obtain, I propose that in addition to the mereological concepts of material and temporal parts, branch-like parts exist. I then use a self-locating approach to treating probabilities as the credences of a rational agent, where the probability of some outcome corresponds to branch weight. This one-world model thus has the capacity to reproduce the predictions of the Born rule while addressing concerns over the apparent frivolity of many-world interpretations.

In many approaches to quantum mechanics, it is common to adopt the eigenstateeigenvalue link (EEL) to describe how the quantum state of a system represents its properties (Fletcher & Taylor, 2021). Any determinable property A of some system can be represented by a self-adjoint operator  with eigenstates |ψ_i⟩ , where the corresponding determinates are given by eigenvalues a_i . EEL states that the system instantiates the property a i just in case it is in the eigenstate |ψ_i⟩ . In Everettian quantum mechanics (EQM), however, the system never enters an eigenstate of any operator that represents a nontrivial determinable of physical relevance; the universal wave function evolves unitarily without collapse, such that for any quantum mechanical process with multiple possible outcomes, decoherence ensures that each possible outcome obtains along a distinct emergent branch. Thus, no Everettian system instantiates nontrivial properties at the most fundamental level of description. This clearly fails to tell the whole story about property instantiation; from the perspective of agents within the emergent branching structure, unique outcomes do obtain and systems have determinate properties. Currently, there is no principle that adequately links the mathematical formalism of EQM to the emergent physical properties instantiated along decoherent branches.

We propose a simple solution: a branch-relative EEL, which states that relative to some branch, the system instantiates the determinate represented by a_i just in case it is in the state |ψ_i ⟩ . This link then allows us to connect the most fundamental description of reality—the universal wave function—to the properties that we observe relative to branches. It is a natural extension of EEL to Everett’s (1957) original relative states formulation, where the “relative state” is just the state relative to a particular branch.

This solution alone may not address all the controversies surrounding the application of EEL to EQM. For instance, Wallace (2019) argues that according to Hegerfeld’s theorem, if a system does not determinately possess some property at some time in the future, then it does not determinately possess that property at any future time, even if it possesses that property in the present. Consequently, a system can only possess a property for at most one instant or for nearly all instants. On this basis, Wallace dismisses EEL as “useless.”

We reconstruct a stronger, more formal version of Wallace’s argument and show that it assumes that the system has a time-independent Hamiltonian. Since interacting subsystems generally have time-dependent reduced Hamiltonians, we propose a second relativision for EEL: relative to some emergent branch and some subsystem, the system instantiates the determinate represented by a_i just in case it is in the reduced state |ψ_i ⟩ . Thus modified, EEL usefully connects the fundamental description of physical reality to emergent properties in branches of the worldly subsystems whose behavior we aim to represent.

There has been a lot of productive discussion about what Bohr’s philosophy of complementarity says. We focus instead on its historical role in pedagogy and research, focusing on relationships between research leaders and their students (mentors and mentees, for short). We find that complementarity is characteristically associated with a particular form of bad epistemic behavior: epistemic infringement, where a mentor systematically contravenes the social and epistemic norms that usually govern their relationship with mentees in a manner that encroaches on the epistemic agency of the latter.  

We argue that Bohr sets the template for this social function of complementarity when he introduces the philosophy in his Como lecture of 1927. Characteristic of epistemic infringement is the abuser’s appeal to the very norms being violated to justify their violation. To illustrate this concept, imagine Sarah, a graduate student, wants to go to a prestigious conference but lacks the funds; her mentor, Peter, offers to cover all her fees if she keeps the source of the money a secret. Peter chides Sarah when she declines the offer, noting that she is shooting herself in the foot: she needs to go to conferences like these to gain scholarly independence. Of course, Peter’s offer would increase Sarah’s reliance on him by establishing a shared secret, contravening the independence norm. Similarly, Bohr appeals repeatedly to the underdetermination of theoretical analogy (particle or wave?) by experiments available at the time of his writing, urging restraint in committing to one of them—a norm which is well-recognized and widely endorsed today among philosophers of physics. Nonetheless, Bohr uses this appeal to argue that physicists should not work with any analogy: only the Copenhagen school’s formally-defined theory can be used with confidence, he argues, and no visualizable depiction of the quantum world is possible. This talk of the finality of the Copenhagen picture is what Mara Beller has memorably deemed Bohr’s “rhetoric of inevitability.” Our assessment goes one step further, suggesting that this rhetoric served a powerful psychological function: to wit, undermining the agency of would-be opponents and dissenters to the Copenhagen paradigm. 

This function becomes clearer when we analyze cases where research leaders like Bohr appeal to complementarity in their relationships with more junior scientists. We focus on two historical case studies: the relationship between Heisenberg and Bohr from 1926 to 1935, and the relationship between Wheeler and Everett around the time of the former’s trip to Copenhagen to advertise his student's work. In both cases, we argue, the mentors succeed in pressuring their students to abandon pursuing their original interpretations of their work—interpretations which, when later resuscitated, proved to be immensely fruitful for the field. We close by reflecting on how these relationships deviate from Carl Rogers’s positive model for healthy mentorship.

Philosophical exchanges can fail in familiar ways. Interlocutors may misjudge one another’s prior knowledge, lack shared hermeneutic resources, or pursue incompatible conversational aims. I argue that such failures do more than produce awkward or frustrating interactions. Even under conditions of ordinary conversational cooperation, they can systematically contribute to the exclusion of philosophers from marginalized groups. To illuminate a possible mechanism underlying this emergent unfairness, I model conversations between philosophers as a repeated social coordination game played between randomly paired agents.

A round of the game is successful just when it generates social utility, either through genuinely collaborative philosophical engagement or through asymmetric informational exchange in which one interlocutor adopts a socially dominant role while the other merely receives. Using an agent-based model with simple reinforcement learning, I show that when this game is played iteratively, stable patterns of epistemic inequality emerge: minority-group agents increasingly select submissive conversational roles, while majority-group agents increasingly select dominant ones. Crucially, the same pattern arises even in the absence of explicit bias; they can arise solely due to population asymmetry. If the game of philosophy is an adequate idealization of professional philosophical interaction in the relevant contexts, the results suggest a striking conclusion: ordinary, cooperative participation in academic philosophy is not neutral, but can itself help reproduce patterns of unfairness endemic to the discipline.