A Saarbrücken Workshop on:
Philosophical Aspects of
March 15, 2006,
IFOMIS, Saarland University
The workshop is designed to encourage interest in the philosophical questions,
ontological as well as epistemological, that permeate quantum mechanics. The four talks
have no other underlying common theme. There is no fee for participation, but
participants are required to register before March 1 by sending an email to
firstname.lastname@example.org. Each session is meant to consist of a 30
minute presentation followed by 30 minutes of discussion.
1:00 pm Barry Smith (IFOMIS), “Quantum Mechanics and Realism”
2:15 Ingvar Johansson (IFOMIS), “Ontology Instead of Epistemology?”
3:45 Daniel Schoch (Department of Philosophy), “The Role of Locality in
Impossibility Theorems for Hidden Variables”
5:00 Uwe Meixner (Department of Philosophy), “On Teasing Philosophical
Significance Out of Quantum-Mechanical Results”
Place: IFOMIS conference room (house A2:4, room 1.32).
Barry Smith: M. Lockwood in The Grain Problem (1993) points out that “people are
very apt to suppose that only microstructure is, so to speak, God given, and that any
higher level of structure is, at best, ontologically or metaphysically derivative, and at
worst, a mere conceptual artefact.” We shall show how, on the basis of the consistent
histories interpretation of quantum mechanics advanced by Omnés, Gell-Man, and
others, one can do justice to the fact that there are not only quantum-level structures but
also all those other structures at higher levels of granularity which are presupposed by
sciences such as chemistry, biology, astronomy, and so forth.
Ingvar Johansson: Some philosophers have claimed that there are two completely
different ways in which entities can exist in time. In this vein, W.E. Johnson
distinguished a hundred years ago between “continuants” and “occurrents”; more
recently, David Lewis has distinguished between “endurants” and “perdurants”. I will
introduce a similar distinction between (i) universals whose instances necessarily either
endure (are continuants) or are punctual, and (ii) universals whose instances necessarily
perdure (are occurrents). All kinds of energy so far used and discussed in physics are of
the first kind, but a dimensional analysis of QM energy shows that some such energy
may in principle also be regarded as being of the second kind. On the latter
interpretation, the uncertainty relation for energy can be seen as not laying down
temporal uncertainty requirements for classical (enduring or punctual) energy but as
stating a law for perduring “time-extended energy”. I have published a paper about this:
“Planck’s Constant and Necessarily Time-Extended Phenomena” (1999).
Daniel Schoch: It is currently assumed that no-go theorems for hidden variable
interpretations of quantum mechanics, such as Bell’s Theorem, require the following two
assumptions for a certain quantum state: 1. (Reality) Quantum observables have a
counterpart in reality independently of its measurement; and 2. (Locality) Absence of
causal or stochastic interdependence of space-like events. Bohm’s hidden variable theory
seems to be perfectly compatible with this view, since it violates the locality principle.
Three arguments shall demonstrate that the locality condition is not necessary to
derive an impossibility result. First, A. Fine has shown that Bell’s inequality is indeed
equivalent to the existence of joint probabilities for a specific experimental setup.
Second, a simple proof of Bell’s inequality can be formulated with reality assumptions
alone for the same setup. Third, in a more general framework including mixed states, a
factorisation condition implying locality follows already from a representation of a
mixture of states as a mixture of representation of these states.
Consequently, Bell’s theorem shows a lack of reality, not of locality. This is reflected
in Bohms ontology, where electrons are real particles, but spin is not represented by an
objective property of these particles in his model.
Uwe Meixner: The experimentally confirmed violation of Bell’s inequalities is supposed
to show that there is no hidden-variable theory which preserves causal locality and is in
agreement with the empirical findings (as, in fact, is QM). But the alleged consequences
of the violation are not easily substantiated. It is not easy to find out what precisely is
violated by the experiments, and what precisely are the assumptions that must therefore
be drawn into doubt. In fact, neither locality nor “hidden-variableness” appear to be
among those assumptions. Let’s see …