As it stands, QBism faces two problems, an epistemic and a semantic one: That it is unclear how, on QBism, an agent can coherently abduce the existence of others and an external, mind-independent world, and that it is unclear how talk of that world even becomes meaningful within the QBist framework. I will here go into elements of phenomenology that could potentially help in solving these problems, but also into what I see as their limitations within ‘phenomenology proper’. I will then go back to Kant, in whose writings some of these phenomenological ideas are rooted, and make a big leap forward, in suggesting a broadly ‘neo-Kantian’ constructivism that I believe evades both problems.
As it stands, QBism faces two problems, an epistemic and a semantic one: That it is unclear how, on QBism, an agent can coherently abduce the existence of others and an external, mind-independent world, and that it is unclear how talk of that world even becomes meaningful within the QBist framework. I will here go into elements of phenomenology that could potentially help in solving these problems, but also into what I see as their limitations within ‘phenomenology proper’. I will then go back to Kant, in whose writings some of these phenomenological ideas are rooted, and make a big leap forward, in suggesting a broadly ‘neo-Kantian’ constructivism that I believe evades both problems.
QBism may be the most significant contribution to the search for meaning in quantum mechanics since Bohr, even as Bohr's philosophy remains the most significant revision of Kant's theory of science. There are two ironies here. Bohr failed to realize the full extent of the affinity of his way of thinking with Kant's, and QBists fail to realize the full extent of their agreement with Bohr. While Bohr's discovery of contextuality updates Kant's transcendental philosophy in a way that leaves the central elements of the latter intact, Kant's insight into the roles that our cognitive faculties play in constructing physical theories can considerably alleviate the difficulties that Bohr's writings present to his readers. And while throwing a QBist searchlight on Bohr's writings can further alleviate these difficulties (as well as reveal the presence in them of the salient elements of QBist thought), Bohr's writings can in turn provide answers to important questions that QBism leaves unanswered (and also allay some of QBism's excesses). In the final sections I confront the two most impenetrable mysteries yet unearthed: making sense of quantum mechanics, and the dual mystery of making sense of (i) the existence of consciousness in a seemingly material world and (ii) the existence in consciousness of a seemingly material world. Here the relevant arguments are framed in the context of the philosophy of the Upanishads, according to which we (as Schrödinger put it) "are all really only various aspects of the One." There is no world that exists out of relation to consciousness, but there are different poises of consciousness. In particular, there is a poise of consciousness peculiar to the human species at this point in time, and there are poises of consciousness that are yet to evolve (and that may be essential to averting the calamities towards which humanity appears to be heading).
This article explores the relationship between Kantian epistemology and QBism, a modern interpretation of quantum mechanics. QBism reconceives scientific objects not as independent entities but as phenomena synthesized through the observer's active role. It emphasizes the interdependence of knowledge and observation, rejecting the notion of a pre-existent, absolute reality. Much like Immanuel Kant's assertion that the thing-in-itself lies outside human cognition, QBism denies ontological status to the unobservable or unexperienced, grounding objectivity in intersubjectivity: the shared cognitive structures of human agents. Within this Critical framework, I address an objection raised by Carlo Rovelli, who critiques QBism for anchoring reality to the observer, claiming it risks falling into idealism by positioning the subject outside nature. Rovelli defends a relational view, situating the observer within the world as describable by the same physical laws that apply to all objects. In response, I argue that the QBist observer represents a universal human subject, not a single determinate agent and that intersubjective agreement ensures objectivity without collapsing into solipsism.
The interpretation of quantum mechanics known as QBism developed out of efforts to understand the probabilities arising in quantum physics as Bayesian in character. But this development was neither easy nor without casualties. Many ideas voiced, and even committed to print, during earlier stages of Quantum Bayesianism turn out to be quite fallacious when seen from the vantage point of QBism. I trace the history of what we might call “proto-QBism” becoming QBism proper, showing that the process was one of becoming consistently Jamesian. But William James and phenomenology are evolutionary cousins, and so guided by QBism's history, I will sketch ways in which phenomenological turns may be inspirational for future developments in the QBist project. The prize, I will argue, would be if phenomenology can evoke a new technical development in the reconstruction of quantum theory or the understanding of the classical limit.
In this programmatic article, our aim is to sketch the outlines of a phenomenological constitution of quantum mechanics, thus drawing the ultimate consequence of previous phenomenological approaches to this theory. In other terms, we wish to show a way to ascend from the situated lived experience of a knowing and acting subject, to the structure and use of the quantum formalism. QBism (Quantum Bayesianism), with its motivated focus on lived experience, and its decision to take the elementary epistemic attitudes of agents as primitives of its axiomatics, will prove a decisive step to progress in this direction.
This is the first volume that focuses specifically on phenomenological approaches to quantum mechanics. It is also the first volume focusing on the philosophical implications of QBism. This coincidence is not accidental. Phenomenology's rich potential for our understanding of quantum mechanics has long been overlooked by analytic philosophers and phenomenologists alike. The experience-first approach of phenomenology, its descriptive methodology, and Husserl's critique of mathematization do not sit well with “mainstream” analytic philosophy of physics. But as this volume will demonstrate, it sits nicely with the basic tenets of QBism. Conversely, QBism constitutes the most consistent and best-developed interpretation of quantum mechanics that fully embraces the Bohrian idea that a proper understanding of science must be based on the concept of experience. However, since its inception in the early 2000s, QBism has struggled to connect with the philosophical community. Not only are the underlying intuitions shaping and dominating contemporary philosophy of quantum mechanics—namely, that a scientific theory must be purged of all subjective and operational notions such as “experience” or “measurement” and that, consequently, a successful approach to quantum mechanics must be formulated as a “quantum theory without observers”—at odds with QBism. It seems that sometimes the incommensurability already starts at the level of the basic conceptual framework which, in the case of mainstream analytic philosophy, is not very well suited to express some of QBism's main tenets. Considering this situation, the main hypothesis of this volume is that phenomenology and QBism are natural bedfellows, and that both can profit from mutual exchange. In order to make this exchange as profitable as possible, the aim of this introductory chapter is to identify, clarify, and motivate some of the cornerstones of phenomenological approaches to quantum mechanics, to shed light on the main ideas and virtues of QBism, and to discuss points of contact and points of possible conflict between these two projects.
The interpretation of quantum theory known as QBism argues that many elements of the formalism have a subjective interpretation. At the same time, QBism claims to be a broadly realist programme. This implies that reality in QBism must be somehow founded upon an agent's subjective experiences (measurement outcomes). To make this idea more precise, we propose to interpret QBism's “experiences” as synonymous with the concept of “perceived phenomena” in phenomenology. This suggests an approach to ontology in which objects can only be physically real if they are in principle observable. But what does “observable” mean? Are atoms, electromagnetic fields, quantum states, or probabilities observable? Here we discuss the different answers to this question given by QBists and phenomenologists, and attempt to reconcile them.