Their cause, he asserts, is "the industry of our forefathers ("l'industrie de nos premiers pères")." He adds later that bronze and iron implements imitate the uses of the stone ones, suggesting a replacement of stone with metals. Mahudel is careful not to take credit for the idea of a succession of usages in time but states: "it is Michel Mercatus, physician of Clement VIII who first had this idea". He does not coin a term for ages, but speaks only of the times of usages. His use of "l'industrie" foreshadows the 20th century "industries," but where the moderns mean specific tool traditions, Mahudel meant only the art of working stone and metal in general.