Abstract Recently several philosophers including Huw Price, Peter Lewis, and David Lewis have argued that on one interpretation of quantum theory (genus Indeterminacy, species No Collapse) death is an illusion.1 Taking Schroedinger’s unhappy cat as the standard example, this interpretation tells us that it is as if the whole universe splits into two copies in one of which the cat survives and in the other there is a corpse. Fission into a living organism on the one hand and a corpse on the other is, most of us agree, a way of surviving.2 So we arrive at the first premise, namely that organisms survive situations like that of SchrÖdinger’s cat.
Abstract Recently several philosophers including Huw Price, Peter Lewis, and David Lewis have argued that on one interpretation of quantum theory (genus Indeterminacy, species No Collapse) death is an illusion.1 Taking Schroedinger’s unhappy cat as the standard example, this interpretation tells us that it is as if the whole universe splits into two copies in one of which the cat survives and in the other there is a corpse. Fission into a living organism on the one hand and a corpse on the other is, most of us agree, a way of surviving.2 So we arrive at the first premise, namely that organisms survive situations like that of SchrÖdinger’s cat.
Abstract The prospect, in terms of subjective expectations, of immortality under the no‐collapse interpretation of quantum mechanics is certain, as pointed out by several authors, both physicists and, more recently, philosophers. The argument, known as quantum suicide, or quantum immortality, has received some critical discussion, but there hasn't been any questioning of David Lewis's point that there is a terrifying corollary to the argument, namely, that we should expect to live forever in a crippled, more and more damaged state, that barely sustains life. This is the prospect of eternal quantum torment. Based on some empirical facts, I argue for a conclusion that is much more reassuring than Lewis's terrible scenario. 1
Erwin Schrodinger first described the thought-experiment which has since become known as 'the paradox of Schrodinger's cat' 51 years ago. In recent years, popular accounts of quantum mechanics have tended to adopt one or other of the philosophically most extreme solutions to this paradox, i.e. the consciousness hypothesis or the many worlds interpretation. The author attempts to redress the balance by describing what he takes to be the orthodox solution to the paradox which explains the paradox, without recourse to such counterintuitive notions as a cat simultaneously dead and alive or a universe continually splitting into multiple worlds, as being due to a misapplication of the quantum formalism.
The interplay between non-relativistic quantum theory and metaphysics has generated radically opposed interpretations for quantum theory: Niels Bohr's 'orthodox' interpretation, and Einstein's 'realist' one. Out of this debate emerged the classical first-generation paradoxes of quantum theory: Schrodinger's Cat and the Einstein-Podolsky-Rosen paradoxes. And more recently a range of new paradoxes has emerged from the work of J.S. Bell which questions the `local' nature of quantum theory, prefiguring a return either to an action-at-a-distance metaphysics or to a radically holistic conception of matter. This book outlines the contours of these debates, and presents an interpretation of quantum theory which, while metaphysically realist, resolves most of the paradoxes. This interpretation takes quantum systems to be fuzzy particles, piloted by fields of propensities which are represented by density operators on Hilbert space; and constitutes, in part, a return to an earlier view of quantum systems advanced by De Broglie, Schrodinger, Born, and Einstein. A book for philosophers and physicists who are interested in the philo sophy o f science.
Abstract To reach the point I want to discuss, I must begin with a sketchy review of quantum mechanics. I apologise to those of you who know this material already, perhaps better than I do. But it will be an opinionated review: some of my opinions are eccentric. So there may be something in it even for those who are already expert. Quantum mechanics is, in a nutshell, the theory of suprpostons. To introduce this concept, I begin with the standard account of the benzene ring-an account so well entrenched in organic chemistry that it would probably survive even if its quantum-mechanical foundation crumbled away beneath it. The benzene ring is a hexagon of carbon atoms, each with a hydrogen atom attached. Replace two adjacent hydrogens with two different substituents, so that we can unambiguously number the sides of the hexagon. Two structures conform to the rules of valence: one with double bonds on the odd-numbered sides, another with double bonds on the even-numbered sides (see Figure 1).The molecule reacts sometimes as if it had one structure, sometimes as if it had the other. Yet we do not think that a population of molecules is a mixture of the two structures. Neither do we think that each molecule oscillates rapidly between one structure and the other. Neither do we think that the molecule has a betwixt-and-between structure- there is no such thing as a bond midway between double and single. Rather, we think that each molecule is in a superposition: a state objectively indeterminate between the two structures. Objective indeterminacy is multiplicity: a cloud of indeterminate extent, for instance, is really many clouds, almost but not quite identical to one another [Unger 1980; Lewis 1999b]. Likewise a molecule with an objectively indeterminate structure is really two coexisting molecules, one with one structure and one with the other. (Or at any rate, two things that are molecule-like except for from their coexistence with one another.)
Abstract In ‘How Many Lives Has Schro dinger’s Cat?’ David Lewis argues that the Everettian no-collapse interpretation of quantum mechanics is in a tangle when it comes to probabilities. This paper aims to show that the difficulties that Lewis raises are insubstantial. The Everettian metaphysics contains a coherent account of probability. Indeed it accounts for probability rather better than orthodox metaphysics does. On 27 June 2001, not four months before his untimely death, David Lewis delivered the third Jack Smart Lecture at the Australian National University. His title was ‘How Many Lives has Schro dinger’s Cat?’ > and he spoke on a topic which is absent from his published writings, the interpretation of quantum mechanics. More specifically, he discussed the ‘no-collapse’ interpretation of quantum mechanics pioneered by Hugh Everett III [1957]. Lewis allowed that this interpretation offers initial theoretical attractions, but also argued that it suffers from irremediable flaws. If you have heard of Everett because of his association with the ‘many-worlds’ interpretation of quantum mechanics popularised by Bryce Dewitt [1970; 1973], you might suppose that there is some affinity between the no-collapse interpretation and Lewis’s philosophical realism about possible worlds. But this would be a mistake. While Everett’s interpretation does add extra ‘branches’ to the reality recognized by common sense, these additions fall far short of Lewis’s multiplication of worlds. For a start, the extra ‘branches’ that Everett adds to reality all lie within the actual world that evolves from the actual initial conditions in line with the actual laws of physics-these branches by no means include all possibilities. Moreover, Everett’s branches are best conceived, not as sundering’s of the whole universe, but rather as entities that spread out causally at finite speeds, ‘like ripples on a pond’, as Lewis puts it. For example, in the Schro dinger’s Cat experiment, firstthe photon branches into a deflected and undeflected version when it passes through the half-silvered mirror; thenthe detector branches into a triggered and untriggered state when it interacts with the photon; thenthe poison bottle branches into a smashed bottle and an unsmashed bottle under the influence of the detector; and so on, culminating in the cat branching into a live and dead cat, and the human observer branching into a self who sees a live cat and a self who sees a dead cat. >
The most discussed of ``live'' metaphors in physical sciences is that of the Schrödinger cat. Introduced in the early, but mature days of the new quantum theory, in 1935, the parable of the cat has provoked and enlivened debates on the meaning of the quantum theory, on the ontology of the quantum wavefunction, on the puzzle of the collapse of the wavefunction, on the meaning of quantum measurement, and on the boundary between the quantum world and the classical world. In this article, I will discuss these issues of the quantum theory focussing on various aspects of the metaphor of the Schrödinger cat.