## Section IV

###### Classical Concepts in Quantum Mechanics

Session Chair: Jaume Navarro

Speakers: Arne Schirrmacher, John Stachel, Kristian Camilleri, Anthony Duncan and Michel Janssen

##
*Arne Schirrmacher*

## Heisenberg's Ladder Didn't Fall.

The conclusion of Wittgenstein's Tractatus (6.54, before he recommends silence for the unspeakable, published 1921 in Annalen der Naturphilosophie) *More Heisenberg's Ladder Didn't Fall.*

##
*John Stachel*

## Bohr: Complementarity and Correspondence

Exchanges with Einstein during the 1920s contributed to Bohr's development of the concepts of complementarity and correspondence in the late 1920s and 1030s. *More Bohr: Complementarity and Correspondence*

##
*Kristian Camilleri*

## The Doctrine of Classical Concepts in Historical Perspective

It is widely recognised that Bohr’s view of the indispensability of classical concepts plays a central role in his interpretation of *More The Doctrine of Classical Concepts in Historical Perspective*

##
*Anthony Duncan, Michel Janssen*

## (Never) mind your p's and q's: Von Neumann versus Jordan on the Foundations of Quantum Theory

In two papers in 1927, Jordan published his version of a general formalism for quantum mechanics now *More (Never) mind your p's and q's: Von Neumann versus Jordan on the Foundations of Quantum Theory*