As he developed his technological interests in the setting of the Musée de l’Homme, Leroi-Gourhan was particularly attentive to the description and documentation of material objects. Cardboard fiches (index cards) with standardized entries – name, function, material, location of finding, etc. – served to ‘bring the milieu of the object’ back into the museum. During his fieldwork in Japan from 1937 to 1939, Leroi-Gourhan refined his documentary approaches, combining ethnographic photographs and object collections. Back in France, however, following the defeat and German occupation, this mass of accumulated fiches became less compelling, especially when Leroi-Gourhan discovered Henri Bergson’s Creative Evolution (1907) with its élan vital and intuitionist philosophy. This notably inspired him to develop the distinction between technical ‘facts’, which are unstable and localized, and technical ‘tendencies’, which are stable, wide-ranging and deterministic. These two concepts, outlined in Evolution et techniques (1943, 1945), characterized his approach to technical phenomena and material civilizations.