Henri Poincaré: The Status of Mechanical Explanations and the Foundations of Statistical Mechanics

The first goal of this paper is to show the evolution of Poincaré’s opinion on the mechanistic reduction of the principles of thermodynamics, placing it in the context of the science of his time. The second is to present some of his work in 1890 on the foundations of statistical mechanics. He became interested first in thermodynamics and its relation with mechanics, drawing on the work of Helm-holtz on monocyclic systems. After a period of skepticism concerning the kinetic theory, he read some of Maxwell’s memories and contributed to the foundations of statistical mechanics. I also show that Poincaré's contributions to the founda-tions of statistical mechanics are closely linked to his work in celestial mechanics and its interest in probability theory and its role in physics

Models as make-believe

In this paper I propose an account of representation for scientific models based on Kendall Walton’s ‘make-believe’ theory of representation in art. I first set out the problem of scientific representation and respond to a recent argument due to Craig Callender and Jonathan Cohen, which aims to show that the problem may be easily dismissed. I then introduce my account of models as props in games of make-believe and show how it offers a solution to the problem. Finally, I demonstrate an important advantage my account has over other theories of scientific representation. All existing theories analyse scientific representation in terms of relations, such as similarity or denotation. By contrast, my account does not take representation in modelling to be essentially relational. For this reason, it can accommodate a group of models often ignored in discussions of scientific representation, namely models which are representational but which represent no actual object

Maurice Allais on the quantity theory of money: the ontological restatement

International audienceThis paper is about a little known part of Allais’ oeuvre, namely his restatement of the quantity theory of money. It shows that this restatement contains an original refinement of the notion of stability of the relative demand for money. To explain this refinement, this essay investigates Allais’ concept of psychological time – a concept strongly emphasised but not duly examined by most of his commentators. It shows how Allais’ restatement of the quantity theory amounts – in the final analysis – to a theory of time. It explores an analogy, Allais mentioned, between his quantity theory and the theory of relativity in physics, revealing thereby the ontological nature of this restatement