46 research outputs found
Explaining the Unobserved: Why Quantum Theory Ain't Only About Information
A remarkable theorem by Clifton, Bub and Halvorson (2003) (CBH) characterizes quantum theory in terms of information--theoretic principles. According to Bub (2004, 2005) the philosophical significance of the theorem is that quantum theory should be regarded as a ``principle'' theory about (quantum) information rather than a ``constructive'' theory about the dynamics of quantum systems. Here we criticize Bub's principle approach arguing that if the mathematical formalism of quantum mechanics remains intact then there is no escape route from solving the measurement problem by constructive theories. We further propose a (Wigner--type) thought experiment that we argue demonstrates that quantum mechanics on the information--theoretic approach is incomplete
Maxwellâs Demon in Quantum Mechanics
Maxwellâs Demon is a thought experiment devised by J. C. Maxwell in 1867 in order to show that the Second Law of thermodynamics is not universal, since it has a counter-example. Since the Second Law is taken by many to provide an arrow of time, the threat to its universality threatens the account of temporal directionality as well. Various attempts to âexorciseâ the Demon, by proving that it is impossible for one reason or another, have been made throughout the years, but none of them were successful. We have shown (in a number of publications) by a general state-space argument that Maxwellâs Demon is compatible with classical mechanics, and that the most recent solutions, based on Landauerâs thesis, are not general. In this paper we demonstrate that Maxwellâs Demon is also compatible with quantum mechanics. We do so by analyzing a particular (but highly idealized) experimental setup and proving that it violates the Second Law. Our discussion is in the framework of standard quantum mechanics; we give two separate arguments in the framework of quantum mechanics with and without the projection postulate. We address in our analysis the connection between measurement and erasure interactions and we show how these notions are applicable in the microscopic quantum mechanical structure. We discuss what might be the quantum mechanical counterpart of the classical notion of âmacrostatesâ, thus explaining why our Quantum Demon setup works not only at the micro level but also at the macro level, properly understood. One implication of our analysis is that the Second Law cannot provide a universal lawlike basis for an account of the arrow of time; this account has to be sought elsewhere
The Mathematical Representation of the Arrow of Time
This paper distinguishes between 3 meanings of reversal, all of which are mathematically equivalent in classical mechanics: velocity reversal, retrodiction, and time reversal. It then concludes that in order to have well defined velocities a primitive arrow of time must be included in every time slice. The paper briefly mentions that this arrow cannot come from the Second Law of thermodynamics, but this point is developed in more details elsewhere
Why the Many-Worlds Interpretation of quantum mechanics needs more than Hilbert space structure
McQueen and Vaidman argue that the Many Worlds Interpretation (MWI) of quantum mechanics provides local causal explanations of the outcomes of experiments in our experience that is due to the total effect of all the worlds together. We show that although the explanation is local in one world, it requires a causal influence that travels across different worlds. We further argue that in the MWI the local nature of our experience is not derivable from the Hilbert space structure, but has to be added to it as an independent postulate. This is due to what we call the factorisation-symmetry and basis-symmetry of Hilbert space
A physicalist account of multiple realizability in the special sciences
Multiple realizability seems to be empirically justified and provides the conceptual basis for the autonomy of the special sciences. But it is mysterious. In this talk I propose a new reductionist approach to the special sciences that removes the mystery: I explain why the special sciences kinds appear to be multiply realized although they are identical with physical kinds and in what sense the special sciences kinds and laws are autonomous although they are physical laws. This approach is based on the approach by Hemmo & Shenker (2012) to the reduction of thermodynamics to statistical mechanics
Is the Mentaculus the Best System of Our World?
Barry Loewer and David Albert put forward a theory that they call âThe Mentaculusâ, which they claim to be âarguably a complete scientific theory of the universeâ. Albert and Loewerâs Mentaculus is an expanded version of their version of statistical mechanics. On their view - as recently updated by Loewerâs âPackage Deal Approachâ - The Mentaculus is the âbest systemâ of our world in the Lewis-style sense of this term: it contains a partial description of the fundamental reality (âThe Humean baseâ) and provides the optimal balance between informativeness and simplicity. The Mentaculus has other advantages, in particular, it is reductionist in the sense that it unifies all the sciences, and it is physicalist in the sense that the account of everything is ultimately based on physics. In this paper we examine the extent to which The Mentaculus is reductionist and physicalist. We compare it with âFlat Physicalismâ, which is our version of expanded statistical mechanics, that is a reductive type-type physicalist identity theory of everything that there is. The Mentaculus is less reductionist than Flat Physicalism, since whereas both theories assume the fundamental microdynamics and suitable contingent facts, The Mentaculus assumes the Past Hypothesis and a Statistical Postulate, that Flat Physicalism derives from the microdynamics and the contingent facts. Additionally, Flat Physicalism derives from the latter all the special sciences kinds and laws, while The Mentaculus does not contain any explanatory account of such reduction. Therefore, Flat Physicalism is arguably âbetterâ than The Mentaculus in the âbest systemâ sense of the term
Why Functionalism Is a Form of âToken-Dualismâ
We present a novel reductive theory of type-identity physicalism (called Flat Physicalism), which is inspired by the foundations of statistical mechanics as a general theory of natural kinds. We show that all the claims mounted against type-identity physicalism in the literature donât apply to Flat Physicalism, and moreover that this reductive theory solves many of the problems faced by the various non-reductive approaches including functionalism. In particular, we show that Flat Physicalism can account for the (alleged) appearance of multiple realizability in the special sciences, and that it gives a novel account of the genuine autonomy of the kinds and laws in the special sciences. We further show that the thesis of genuine multiple realization, which is compatible with all forms of non-reductive approaches including functionalism, implies what we call token-dualism; namely the idea that in every token (that partakes in this multiple realization) there are non-physical facts, which may either be non-physical properties or some non-physical substance. In other words, we prove that non-reductive kinds necessarily assume non-reductive tokens, i.e., token dualism. Finally, we show that all forms of non-reductive approaches including functionalism imply a literally multi-leveled structure of reality
The multiple-computations theorem and the physics of singling out a computation
The problem of multiple-computations discovered by Hilary Putnam presents a deep
difficulty for functionalism (of all sorts, computational and causal). We describe in out-
line why Putnamâs result, and likewise the more restricted result we call the Multiple-
Computations Theorem, are in fact theorems of statistical mechanics. We show why
the mere interaction of a computing system with its environment cannot single out a
computation as the preferred one amongst the many computations implemented by
the system. We explain why nonreductive approaches to solving the multiple-
computations problem, and in particular why computational externalism, are dualistic
in the sense that they imply that nonphysical facts in the environment of a computing
system single out the computation. We discuss certain attempts to dissolve Putnamâs
unrestricted result by appealing to systems with certain kinds of input and output
states as a special case of computational externalism, and show why this approach is
not workable without collapsing to behaviorism. We conclude with some remarks
about the nonphysical nature of mainstream approaches to both statistical mechanics
and the quantum theory of measurement with respect to the singling out of partitions
and observables
A Dilemma for Davidsonâs Anomalous Monism
Is freedom compatible with determinism? Davidson (in âMental Eventsâ) famously rephrased this question by replacing âfreedomâ with âanomaly of the mentalâ, that is, failure to fall under a law. In order to prove that the anomaly of the mental is compatible with other conjectures he makes, in particular that: (a) there is psycho-physical causation; (b) âwhere there is causality, there must be a lawâ (Davidson 1970, p. 208); and (c) the mental supervenes on the physical, Davidson proposed a model (i.e., an interpretation under which all these conjectures are true), that came to be known as anomalous monism. Accepting (as working hypotheses) all of Davidsonâs conjectures, we compare the structure of Davidsonâs argument with that of Einsteinâs argument for the special theory of relativity. This leads us to an exposition of Davidsonâs ontology in terms that are inspired by recent results in the philosophy of physics, that is, in terms of fundamental ontology and high-level coarse-grained descriptions. We explain in what sense Davidsonâs model is a principle theory (in Einsteinâs terms) and discuss some requirements that the constructive theory underlying Davidson's principle approach must satisfy. We propose two constructive theories of description that may underlie Davidson's approach and this deeper structure leads us to formulating a dilemma according to which Davidson's approach entails either a non-physicalist type-identity reductive and monistic structure of events; or else it entails a structure of events that requires what we call token-substance dualism. We consider some issues which seem to suggest that the first horn of this dilemma collapses into a reductive type-identity physicalist theory, contrary to Davidson's intent. Finally, we show how Davidson's achievement of accounting for some freedom of the mental from the physical and the anomaly of the mental within anomalous monism can be achieved in a fully reductive type-identity physicalist theory