The Many Worlds Interpretation of quantum mechanics - arguably our most powerfully predictive scientific theory to date - describes a branching Universe composed of an infinite number of quasi-classical macroscopic physical worlds. Though elegant in its straightforward rendering of the mechanics, the Many Worlds Interpretation presents a challenge for understanding identity over time. If we wish to preserve the notion of strict numerical identity, we are faced with the choice between: denying the transitivity of identity; very short-lived lives with near constant death; or accepting that the world is filled with many more individuals than we previously dreamed. In adopting a perdurantist account of identity over time, I argue for this last option. But questions remain about the relationship that branching individuals have to those from whom they’ve split. In this dissertation, I develop a novel account that I call Many Worlds Counterparts. This theory takes its inspiration from Lewis’s Counterpart Theory in offering a modal analysis of de re possibility, but avoids the major challenges that Lewis’s theory faces.
The Many Worlds Interpretation of quantum mechanics - arguably our most powerfully predictive scientific theory to date - describes a branching Universe composed of an infinite number of quasi-classical macroscopic physical worlds. Though elegant in its straightforward rendering of the mechanics, the Many Worlds Interpretation presents a challenge for understanding identity over time. If we wish to preserve the notion of strict numerical identity, we are faced with the choice between: denying the transitivity of identity; very short-lived lives with near constant death; or accepting that the world is filled with many more individuals than we previously dreamed. In adopting a perdurantist account of identity over time, I argue for this last option. But questions remain about the relationship that branching individuals have to those from whom they’ve split. In this dissertation, I develop a novel account that I call Many Worlds Counterparts. This theory takes its inspiration from Lewis’s Counterpart Theory in offering a modal analysis of de re possibility, but avoids the major challenges that Lewis’s theory faces.
This paper examines personal identity in the context of the Everett interpretation of Quantum Mechanics. According to Everett, the universe branches many – perhaps an infinite number of – times per second. This leads to a universe in which many versions of ‘you’ exist, many of whom are living different lives to yours. How are we to make sense of the continuation of the self in this context? This is of particular importance for Christian theism, which is committed to an enduring self that can be held responsible for past actions and can develop an ongoing relationship with God. The paper argues that the best way to understand identity in the Everettian world as fundamentally narrative in nature.
Abstract What does realism about the quantum state imply? What follows when quantum theory is applied without restriction, if need be, to the whole universe? These are the questions which are debated in this book. All the chapters start from the point of realism, and based on the need, or the aspiration, for a theory that unites micro- and macroworlds, at least in principle. But the further claim argued by some is that if you allow the Schrödinger equation unrestricted application, supposing the quantum state to be something physically real, then this universe is one of countlessly many others, constantly branching in time, all of which are real. The result is the many worlds theory, also known as the Everett interpretation of quantum mechanics. The contrary claim sees this picture of many worlds as in no sense inherent in quantum mechanics, even when the latter is allowed unrestricted scope and even given that the quantum state itself is something physically real. For this picture of branching worlds fails to make physical sense, let alone common sense, even on its own terms. The status of these worlds, what they are made of, is never adequately explained. Ordinary ideas about time and identity over time become hopelessly compromised. The concept of probability itself is brought into question. This picture of many branching worlds is inchoate, it is a vision, an error. There are realist alternatives to many worlds, some even that preserve the Schrödinger equation unchanged. Twenty chapters, accompanied by commentaries and discussions, examine these claims and counterclaims in depth. They focus first on the question of ontology, the existence of worlds, second on the interpretation of probability, and third on alternatives or additions to many worlds. The introduction offers a helpful guide to the arguments for the Everett interpretation, particularly as they have been formulated in the last two decades.
Abstract Inspired by David Lewis’s work on possible worlds, there has been some discussion about whether the fission of worlds in the quantum many-worlds theory should be considered branching (where fission is like a branching path) or diverging (where the worlds are separate but qualitatively identical until some point of divergence). Several authors favour the latter on the basis that we can delineate worlds that are separate from each other prior to fission using a consistent histories approach. However, these worlds are not entirely independent of each other prior to fission, rendering neither of Lewis’s options fully compelling. I propose that the process is better conceptualised as splitting , analogous to the splitting of classical waves. When an entity splits, it separates into its component parts, each reduced somehow from the original, and so the original entity only partially persists as each of its successors. I propose that understanding many-worlds fission as one world splitting into its component parts aligns more closely with the physics and provides a more natural and intuitive understanding of the fission process.
The many-worlds interpretation offers a fundamental explanation to the seemingly bizarre quantum theory; however, it lacks empirical significance. In this work I put forward the concepts of “nousor” and “counterpart”, and the notion of self structure scheme, by which I argue that the existence of other parallel worlds could be revealed by dream, and those counterparts in different worlds can exchange information through the special nousor to ensure the oneness of counterparts. Many worlds and all lives there follow the rules of correspondence, convergence, limitation, as well as love and hate. Based on the proposed theory, I analyze not only déjà vu phenomenon, but also actual dreams and sleepwalking, to assist us to understand the concept of self. A large database of humanity’s dreams should be constructed for helping predict disruptions both individually and environmentally.
The purpose of this paper is to give an overview of modal realism and many worlds interpretation of quantum mechanics and compare the concepts of many worlds in those two theories. Main source for modal realism is David Lewis' book On the Plurality of Worlds (1986). For many worlds interpretation I rely on Bryce DeWitt and Lev Vaidman. First part of the paper concerns modal realism, second is about many worlds interpretation and third is the comparison of those two. Many worlds in modal realism and many worlds interpretation have the same phenomenology, but are different ontologically. The worlds of modal realism are causally and spatiotemporally separated and have always been, while the worlds of many worlds interpretation are part of a branching universe. That means they were the same world at some point in the past, even though they are equally separated, as the worlds of modal realism are, after the branching.
The nature of branching in the many-worlds interpretation (MWI) of quantum mechanics remains an open question, particularly regarding its locality and compatibility with special relativity. This paper challenges the conventional view that branching is either global or local, demonstrating instead that it is nonlocal for entangled systems. Through a new analysis of the EPR-Bohm experiment, I argue that global branching has several potential issues and can hardly be justified. At the same time, I argue that branching cannot be entirely local, as entangled particles exhibit simultaneous, spacelike-separated branching, manifesting an apparent action at a distance within individual worlds. However, while nonlocal branching suggests the emergence of a preferred Lorentz frame within each world, the multiverse as a whole retains full Lorentz invariance, ensuring no superluminal signaling. By refining the ontology of branching and resolving tensions between MWI and relativistic constraints, this analysis may help advance our understanding of quantum nonlocality and also strengthen MWI's standing as a viable interpretation of quantum mechanics.