Dr. Marij van Strien

September 1 - November 30, 2020

and March 1 - May 31, 2023

Affiliation: University of Wuppertal

Research for a study about:

Quantum mechanics. Causality, and the limits of science. 1920-1940

Abstract of the Research Project:

My main research project at the moment deals with the impact of quantum mechanics on twentieth century philosophy. Quantum mechanics is a very successful theory describing nature at a fundamental level, and at the same time it is routinely presented as mysterious, paradoxical and impossible to understand. My general research question is how the puzzles connected to quantum mechanics have affected the general image of science in the twentieth century.

While in Vienna, I am looking specifically at the engagement of Moritz Schlick and Philipp Frank with the philosophical implications of quantum mechanics. Quantum mechanics was often connected to logical empiricism because of the central role of observations in the theory; at the same time, the fact that causality was thought to be limited in quantum mechanics opened the door to a wide range of speculations concerning free will, vitalism, psychology and religion. Schlick and Frank were faced with the task of revising the concept of causality in the light of the development of quantum mechanics, while guarding the limits of science. This project thus looks at the broader context to debates on the implications of quantum physics for causality at that time, connecting these debates with the issue of the limits of science and the public image of science.

Project-Plan from March 1 - May 31, 2023:

Project 1 - Overcoming Newton in the Twentieth Century: The Development and Rhetorical Uses of the Concept of Classical Physics
Project 2 - Reichenbach and Jordan on the Implications of Quantum Mechanics for Free Will

Online Lecture

The challenge of quantum mechanics to the limits of science and the Vienna Circle's response

Moderator: Iulian Toader

Date: 12/11/2020

Time: 15h00 - 17h00

Plattform: ? | Talks at Physics-meets-Philosophy-in-Vienna

Access: To appear soon


The modern theory of quantum mechanics, developed in 1925-26, has often been seen as a positivistic theory, because of the central role of observations in the theory and the dismissal of questions about the reality of quantum processes independent of measurement. At the same time, in the 1920s and 1930s, it was often concluded that quantum mechanics implies that there is a limit to what can be known scientifically, and this opened the door to a wide range of speculations, in which quantum mechanics was connected with free will, organic life, psychology and religion – connections which were drawn not in the least by quantum physicists themselves. This tension is perhaps nowhere stronger than in the work of Pascual Jordan, one of the leading quantum physicists of the period, who emphasized the positivistic elements in quantum mechanics as well as using it as the basis for an extravagant theory about the essence of organic life and the psychology of the will, a theory which, moreover, had National Socialist overtones. It is thus no wonder that when Jordan published his quantum speculations in *Erkenntnis* in 1934, they were harshly criticized by members of the Vienna Circle. But although Jordan's claims could easily be dismissed, the resulting discussion (to which especially Moritz Schlick and Philipp Frank made extensive contributions) did reveal broader challenges posed by quantum theory: both Heisenberg's uncertainty relations and Bohr's notion of complementarity were often used to argue that there are fundamental limits to physical knowledge, and these possible limits to the scope and unity of science were more challenging to deal with for defenders of the scientific world view.