Poincaré, Le Roy, and the Nouveau positivisme

Henri Poincaré’s philosophy of science has been widely studied and has been related to other important scientific and philosophical figures such as Einstein, Hilbert, Helmholtz, Duhem, and even Bergson. Poincaré refers to many people in his works, but there is one name that appears repeatedly in his texts, in particular when he develops his general views on the value of science. That is Édouard Le Roy. There is a lack of secondary sources on Le Roy’s work and, when compared to Poincaré, references are usually given to Poincaré’s interpretation of his works and not to Le Roy himself. When writing on the value of science, Poincaré structures his discourse as a reply to Le Roy’s views. This paper aims at clarifying why it was so important for Poincaré to reply to Le Roy. To do that, we will discuss the figure of Le Roy in the context of the time, his philosophy (which he called nouveau positivisme), and the relation between Poincaré’s philosophical position and Le Roy’s. This will make Le Roy’s work more familiar to contemporary audiences but will also clarify some controversial aspects in Poincaré’s position.