 These, he claimed, had transformed 17th and 18th century studies of "general grammar" into modern "linguistics", "natural history" into modern "biology", and "analysis of wealth" into modern "economics"; though not, claimed Foucault, without loss of meaning.According to Foucault, the 19th century transformed what knowledge was.Perhaps Foucault's best-known claim was that "Man did not exist" before the 18th century.