# Berlin 2014 – wissenschaftliches Programm

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# AGPhil: Arbeitsgruppe Philosophie der Physik

## AGPhil 3: Symposium Quantum-Classical Divide

### AGPhil 3.4: Hauptvortrag

### Donnerstag, 20. März 2014, 12:00–12:30, Audimax

**Why Physics Needs a Classical World...and How It Can Get One** — •Tim Maudlin — New York University, Department of Philosophy

One basic question about a proposed fundamental physical theory is how it makes contact with empirical data. If a theory does not provide empirically testable predictions then it cannot be part of empirical science, and if the theory is supposed to be a fundamental physical theory then those predictions should be derivable from the account of the world provided by the theory itself. It has never been clear how quantum theory is supposed to meet this demand. Bohr's presentation of the theory had a "two-worlds" character: the microscopic world is represented by a mathematical quantum state, but the laboratory had to be described in "classical language". Bohr's approach provided (somewhat vague) rules for how to derive probabilistic predictions about the latter given a mathematical representation of the former, but did not even aspire to show how the laboratory equipment itself could be understood as a fundamentally quantum-mechanical system. John Bell proposed a general solution to this problem with what he called the "Theory of Local Beables". I will review Bell's general program and discuss several quite different concrete ways it can be realized.