Privileged-perspective realism (PPR) is a version of metaphysical realism that takes certain irreducibly perspectival facts to be partly constitutive of reality. PPR asserts that there is a single metaphysically privileged standpoint from which these perspectival facts obtain. This chapter discusses several views that fall under the category of privileged-perspective realism. These include presentism, which is PPR about tensed facts, and non-multiverse interpretations of quantum mechanics, which the chapter argues, constitute PPR about world-indexed facts. Using the framework of the bird perspective and the frog perspective, it argues that PPR views are motivated by the assumption that the frog perspective is metaphysically primary. The chapter considers case studies of metaphysical interpretations of special relativity and quantum mechanics in order to demonstrate that such motivations for PPR are non-naturalistic. It considers psychological factors that motivate the appeal of PPR views and offers naturalistic explanations of why we should not expect them to lead to good metaphysics of science.
Privileged-perspective realism (PPR) is a version of metaphysical realism that takes certain irreducibly perspectival facts to be partly constitutive of reality. PPR asserts that there is a single metaphysically privileged standpoint from which these perspectival facts obtain. This chapter discusses several views that fall under the category of privileged-perspective realism. These include presentism, which is PPR about tensed facts, and non-multiverse interpretations of quantum mechanics, which the chapter argues, constitute PPR about world-indexed facts. Using the framework of the bird perspective and the frog perspective, it argues that PPR views are motivated by the assumption that the frog perspective is metaphysically primary. The chapter considers case studies of metaphysical interpretations of special relativity and quantum mechanics in order to demonstrate that such motivations for PPR are non-naturalistic. It considers psychological factors that motivate the appeal of PPR views and offers naturalistic explanations of why we should not expect them to lead to good metaphysics of science.
Abstract The theories of pre-quantum physics are standardly seen as representing physical systems and their properties. Quantum mechanics in its standard form is a more problematic case: here, interpretational problems have led to doubts about the tenability of realist views. Thus, QBists and Quantum Pragmatists maintain that quantum mechanics should not be thought of as representing physical systems, but rather as an agent-centered tool for updating beliefs about such systems. It is part and parcel of such views that different agents may have different beliefs and may assign different quantum states. What results is a collection of agent-centered perspectives rather than a unique representation of the physical world. In this paper we argue that the problems identified by QBism and Quantum Pragmatism do not necessitate abandoning the ideal of representing the physical world. We can avail ourselves of the same puzzle-solving strategies as employed by QBists and pragmatists by adopting a perspectival quantum realism. According to this perspectivalism (close to the relational interpretation of quantum mechanics) objects may possess different, but equally objective properties with respect to different physically defined perspectives. We discuss two options for such a perspectivalism, a local and a nonlocal one, and apply them to Wigner’s friend and EPR scenarios. Finally, we connect quantum perspectivalism to the recently proposed philosophical position of fragmentalism.
Abstract Perspectivist positions have been proposed in physics, notably in order to address the interpretive difficulties of quantum mechanics. Recently, some versions of perspectivism have also been proposed in general philosophy of science to account for the plurality of scientific practice. Both kinds of views share the rejection of what they metaphorically call the “view from nowhere”. However, beyond this superficial similarity, they are very different: while quantum perspectivism entertains a concrete notion of perspective associated with individual agents or systems or concrete contexts, perspectival realism adopts a more abstract notion associated with explanatory aims or conceptual schemes. The aim of this paper is to clarify what is at stake with perspectivism in general. The general notion of a perspective, as well as the various attitudes one can entertained towards them, are characterised using the concepts of harmless contradiction and cross-perspectival accessibility. A taxonomy of positions ranging from absolutism to relativism is proposed on this basis. Then the framework is applied to quantum perspectivism and perspectival realism to show its fruitfulness. Finally, I argue that abstract versions of perspectivism are bound to be metaphysically weaker than concrete versions.
Recent no-go theorems challenging the absoluteness of events have highlighted the possibility that dynamical facts in quantum theory are observer-relative. This thesis examines the metaphysical and conceptual foundations of quantum relativism, focusing on Relational Quantum Mechanics (RQM). It analyzes arguments for relativism through Wigner’s Friend and Extended Wigner’s Friend thought experiments, explores the link between relative physical facts and experiences, and offers the first metaphysical definition of "relative facts." The thesis argues: RQM supports a perspectival retro-determination of past events based on later acquisition of information; Quantum relativists must also relativize facts about observers’ experiences; the strongest arguments for relativism lead to unbounded higher-order relativity, precluding any absolute 'view from nowhere'; Only a metaphysical framework that relativized the composition of reality itself can accommodate such an unrestricted iteration. These conclusions deepen our grasp of a thoroughly perspectival quantum world.
This paper examines the metaphysical foundations of Relational Quantum Mechanics (RQM), with special attention to its compatibility with scientific realism. We argue that RQM faces a dilemma. In its original formulation, RQM secures a sparse ontology of relative quantum events, but lacks the world-building structure needed to explain how these events jointly constitute a single, coherent reality of the kind presupposed by scientific realism. Recent discussions have already emphasized the difficulties that RQM faces concerning intersubjective agreement, communication, and the emergence of stable facts. Our contribution is to diagnose these difficulties as symptoms of a deeper metaphysical problem: RQM provides relative facts, but no clear account of what makes them facts of one world. We then assess the revised formulation proposed by Adlam and Rovelli, centered on the Cross-Perspective Links (CPL) principle. While CPL aims to restore intersubjective agreement by guaranteeing consistency across perspectives, we argue that it does so at a significant cost. It introduces observer-independent facts, persistent information-bearing structures, and global consistency constraints that sit uneasily with the relational spirit of the original interpretation. Thus, RQM either remains thoroughly relational but metaphysically too weak to support robust scientific realism, or it repairs this weakness by compromising its own relational foundations.
Realism in Context: The Examples of Lifeworld and Quantum Physics Lifeworld realism and quantum-physical realism are taken as experience-dependent conceptions of the world that become objects of explicit reflection when confronted with context-external discourses. After a brief sketch of the two contexts of experience—lifeworld and quantum physics—and their realist interpretations, I will discuss the quantum world from the perspective of lifeworld realism. From this perspective, the quantum world—roughly speaking—has to be either unreal or else constitute a different reality. Then, I invert the perspective and examine the lifeworld from the standpoint of quantumphysical realism. This conception of the lifeworld has gained momentum from new research results in recent decades. Despite its experiential basis, quantum-physical realism bears an ambiguity akin to that of lifeworld realism. While the perspectival inversion serves to highlight the problem, it also contributes to an improved understanding of lifeworld-realism.
According to scientific realism, science gives us an approximately true description of what the world is like. But what does it mean? In this chapter, we focus on the ontological and metaphysical aspects of this discussion. That is, we are concerned with the following questions: what there is, according to our best scientific theories? And how are these things that theories say exist? We start from the assumption that a genuine scientific realism must deal with these issues. Taking non-relativistic quantum mechanics as a case study, we discuss some of the challenges currently faced by a genuinely realistic stance. We argue, first, that in the ontological aspect, realists are in the same boat as science, that is, without sufficient epistemic justification to adopt the belief in the entities postulated by a single quantum theory, given that experience (currently) is not able to decide between rival theories; in the metaphysical aspect, realists also encounter problems with theory choice, given the possibility of associating more than one metaphysical theory with the description of the entities postulated by each quantum theory. The same goes for structuralist alternatives, since, even if we accept that scientific theories are committed to the existence of structures, but not objects, we still do not know what structures are, metaphysically. Finally, we move forward in the discussion with the meta-Popperian method, which serves to reduce the metaphysical alternatives associated with the ontological postulates of scientific theories. We may not know what the correct alternative is, but we have been able to progressively check which metaphysical alternatives are incompatible with each scientific theory.