What is a physical object according to the theory of quantum mechanics? The first answer to be considered is that given by Bohr in terms of the concept of complementarity. This interpretation is illustrated by way of an example, the two slit experiment, which highlights some of the associated problems of ontology. One such problem is the so-called problem of measurement or observation. Various interpretations of measurement in Quantum Theory, including those of Heisenberg, von Neumann, Everett and Bohr, are compared (...) and contrasted. A second problem concerns whether or not QT can be considered complete and therefore satisfactory as a basis for physics. Various attempts to complete QT by means of the addition of ‘hidden variables’ to the quantum mechanical state function are considered and their aims and achievements assessed. Finally, we investigate some of the characteristic ontological problems for the orthodox interpretation of Relativistic Quantum Theory. -/- . (shrink)

The work of Gleason and of Kochen and Specker has been thought to refute a naïve realist approach to quantum mechanics. The argument of this paper substantially bears out this conclusion. The assumptions required by their work are not arbitrary, but have sound theoretical justification. Moreover, if they are false, there seems no reason why their falsity should not be demonstrable in some sufficiently ingenious experiment. Suitably interpreted, the work of Bell and Wigner may be seen to yield independent arguments (...) for the falsity of naïve realistic approach to quantum mechanics. Quantum mechanics is no more like classical statistical mechanics than its creators thought it was. (shrink)

The transactional interpretation of quantum mechanics, following the time-symmetric formulation of electrodynamics, uses retarded and advanced solutions of the Schrödinger equation and its complex conjugate to understand quantum phenomena by means of transactions. A transaction occurs between an emitter and a specific absorber when the emitter has received advanced waves from all possible absorbers. Advanced causation always raises the specter of paradoxes, and it must be addressed carefully. In particular, different devices involving contingent absorbers or various types of interaction-free measurements (...) have been proposed as threatening the original version of the transactional interpretation. These proposals will be analyzed by examining in each case the configuration of absorbers and, in the special case of the so-called quantum liar experiment, by carefully following the development of retarded and advanced waves through the Mach-Zehnder interferometer. We will show that there is no need to resort to the hierarchy of transactions that some have proposed, and will argue that the transactional interpretation is consistent with the block-universe picture of time. (shrink)

Since the appearance of T. S. Kuhn's The Structure of Scientific Revolutions, scholars from various fields have sought to evaluate their disciplines in the light of Kuhnian criteria for scientific change. In this paper I argue that a new paradigm seems needed in high energy physics, and that there is no more reason to say that matter is made of elementary particles, than to say that it is not. My argument, that high energy physics is approaching a state of crisis, (...) and that a new paradigm is needed, is based on an examination of two events which, according to Kuhn, presage a conceptual revolution: (1) the "old" paradigm of normal science becomes unclear; and (2) this paradigm fails to support normal problem solving research, and scientists begin to use it as if it were merely definitional. After examining the elementary particles paradigm in the light of these two criteria, I conclude that high energy physics is moving from "normal science" to "extraordinary science." I argue neither that a new paradigm has been found, nor that a return to normal science is imminent; instead I attempt to briefly outline some of the conceptual problems in high energy physics to which Heisenberg, Feynman, and others have alluded, but which so far have not been spelled out in any great philosophical detail. No attempt is made to argue about what the specific consequences of these difficulties might be, but merely to begin to clarify the problems facing scientists dealing with elementary particles. (shrink)