Tactile and visual space. Origin of the concept of expanse in Jules Lachelier [Espace tactile et espace visuel. L’origine de la notion d’étendue chez Jules Lachelier]

At the end of the 18th century, the German physician and philosopher Ernst Platner, reporting an observation made on a man born blind, states that a man deprived of the sense of sight cannot have the category of space. This brief observation soon becomes a privileged reference in the debate on the acquired or innate nature of knowledge. One of the main contributions published in France on this subject is a text by Jules Lachelier on the origin of the notion of space. Although quite unknown, "L'Observation de Platner" (1903) showcases some interesting insights on the problem. By relying on an in-depth understanding of the era's psychological debate, Lachelier gives a new shape to the spiritualist positions formulated on the subject, and ends up reconceptualising the dualism between nativism and empiricism.