Certain of Takabayasi's criticism of a causal re-interpretation of the quantum theory are answered in detail. It is indecated how this interpretation can be extended to the Dirac equation, and the problem of the identity of equivalent particles is discussed, for the case of particles that satisfy the Pauli principle. Possible extensions of theory are indicated. Finally, criticisms at the philosophical level are discussed, especially the question of what it means to call a theory "metaphysical" and the reasons why the concept of causality is indispensable in scientific theories.
Certain of Takabayasi's criticism of a causal re-interpretation of the quantum theory are answered in detail. It is indecated how this interpretation can be extended to the Dirac equation, and the problem of the identity of equivalent particles is discussed, for the case of particles that satisfy the Pauli principle. Possible extensions of theory are indicated. Finally, criticisms at the philosophical level are discussed, especially the question of what it means to call a theory "metaphysical" and the reasons why the concept of causality is indispensable in scientific theories.
The disagreement with regard to the validity of the principle of causality, existing to-day among scientists, has its roots in the diversity of definitions of the principle itself rather than in a problematic scientific situation. As far as the formulation of quantum theory is complete its bearing upon philosophical questions can be fixed with precision provided the questions are phrased intelligibly. But a question is intelligible from a scientific point of view only if it satisfies two conditions: (1) the meaning of its terms must be fixed; (2) it must be in accord with the conventions of the science to which the question is put.
Beginning in 1900 with 1-iax Planck's hypothesis of quanta, physics has been embarked on a course which has raised serious questions about the true nature of physical reality, about the foundational assumptions and structures of science, and about the relationships between physical reality and physical theory. In particular, attempts to give a physical interpretation to quantum theory seem to result in "pictures" of nature which are paradoxical. A subatomic entity is described by the theory as exhibiting the properties and behavior of both particle-like phenomena and wavelike phenomena. Since it seems unreasonable that a single entity could be both a point-like mass and a wave spread out through a region of space, quantum theory would seem to be less than satisfactory or less than complete at the interpretational level. The purpose of this dissertation is to investigate the underlying causes of this paradox. The dissertation proceeds by reviewing the development of quantum theory and the emergence of the paradox. Next, the problem of physical interpretation is examined and several of the more significant existing interpretations are discussed and analyzed. Finally, the foundations of science and the general structure of scientific theory are examined in a search for the origins of the paradox. As a result of these investigations and analyses, it is concluded that the paradoxical nature of the physical interpretation of quantum theory is the consequence of certain paradigms and preconceptualizations about physical reality which have been incorporated into the theory at the foundational level. These fundamental assU14ptions produce, within quantum theory, a forced marriage of the plenum and atomic views of physical reality. They also produce an ambiguity with respect to the nature of causality which is charaeteristic of the theory. These problems are reflected in the mathematical formalisms and physical concepts of the theory as well as in its metaphysical foundations. Lastly, methods of resoling the paradox are discussed. It is argued that a successful solution is possible, but that it would involve the creation of a new metaphor-an extension of the present language--which would lead science to a deeper, subquantum level in terms of which the present paradox would vanish.
ABSTRACT The paper aims to bridge the history of quantum theory with its philosophical implications. The focus is not only on the scientific underpinnings of quantum mechanics (these theories emerged as ‘ad hoc’ responses to experimental anomalies) but also on the philosophical ramifications of its probabilistic nature and indeterminacy, which differ from classical realism. The paper examines Dirac's, Bell's, and modern views, focusing on how quantum mechanics (QM) challenges traditional notions of causality, objectivity, and truth while embracing epistemological and metaphysical perspectives. Debates over collapse theories and hidden variables are discussed, as well as Putnam's philosophical outlook, which includes his trenchant involvement with realism, logic, and the measurement problem. Finally, the paper proposes that QM represents a philosophical revolution that renews our understanding of reality, knowledge, and scientific explanation, rather than simply serving as a physical theory for assessing the prospects of quantum philosophy by connecting it to broader aspects such as relativity, causality, and scientific realism.
By re-expressing the generalized Schrodinger equation in its coordinate representation in terms of amplitude and phase of the state vector, a quantum-mechanical change of a system can be made to correspond to an ensemble of classical motions of the system to which is added some internal potential. This ensemble may be taken as the statistical. This enables an alternative formulation of quantum mechanics with which is associated that classical picture. Such a formulation leads, however, if developed straightforwardly according to the picture, to a theoretical scheme quite different from that of ordinary quantum mechanics concerning the problems other than the equation of motion. Furthermore, this formulation is not applicable to Fermions when spin, or exclusion principle is taken into account. Bohm's recent renewed form of the statistical interpretation of quantum mechanics referring to this formulation is criticized in several points. On this formulation we can construct a singular ensemble which is shown to correspond to the transformation kernel of the wave function to infinitesimally later instant, and thus a connection between this formulation and that of Feynman's is taken out. Hydrodynamical picture formally equivalent to the statistical picture in one-body problems is also considered, and from such analogy certain formal generalization of Schrodinger equation is suggested.
The causal interpretation of quantum mechanics, as originally stated by deBroglie and Bohm, had several attractive features. Among these is the possibility that it could address some of the most fundamental questions on quantum phenomena. However, subsequent theoretical conjectures, which have now been included in the orthodox view of the deBroglie Bohm theory, are unphysical and have done much to undermine the original theory's appeal. We, therefore, return to the original theory as our starting point and address one of its perplexing areas: the quantum potential. By avoiding the unphysical conjectures we are led to an understanding of the quantum potential which is distinctly different from that of the orthodox deBroglie Bohm view.
In quantum mechanics, quantum nonseparability is at the core of philosophical debates regarding its meaning. In the context of the process matrix formalism, causal nonseparability characterises quantum processes (connecting the inputs and outputs of different local quantum operations) that are incompatible with any definite causal structure among interacting parties. One talks about indefinite causal orders. A famous example of causally nonseparable processes is called the quantum switch (QS). It is extensively studied in the literature in virtue of its simple architecture and its various implementations in laboratories.The present work will discuss the possible interpretations of the QS's causal nonseparability under the assumption that causal nonseparability is seen as pointing towards novel objective features of nature.It was first defended that a scientific realist approach towards the process matrix formalism, which is an operational theory generalising quantum mechanics, was as much legitimate as any possible antirealist reading, contrary to certain views found in the literature. The reason is that operational formalisms are ontologically and epistemically neutral.From there, the theoretical concepts of interest, namely causal nonseparability and its model-independent counterpart called noncausality, were analysed in more details, in order to highlight in what sense they are distinct from the standard notions of quantum nonseparability and nonlocality in quantum mechanics.The discussion then focused on noncausality. It was argued that noncausality has a strong connection with a notion of temporal nonlocality. In the same way that Bell nonlocality is given different underlying explanations depending on the details of the chosen quantum mechanics' account, noncausality pointing towards temporal nonlocality can be given a variety of underlying descriptions depending on the exact way to interpret the process matrix formalism.The last chapter focused precisely on this particular point, namely on the various ways to understand process matrices and causal nonseparability in a realist context. In order to explore the potential impact of causal nonseparability on spacetime,we shifted from the notion of (indefinite) causal structure to (indefinite) spatiotemporal ones. This shift was allowed under a set of reasonable assumptions regarding the properties of a physical spacetime manifold and the connection between an operational and relativistic notions of causal relations.While different readings were suggested for indefiniteness of spatiotemporal relations, we insisted in particular on an objective understanding appealing to the concept of metaphysical indeterminacy. It was argued that such an approach could prove useful in a more general theoretical context such as quantum gravity, while being already partly supported in standard quantum mechanics.