This article discusses the limits of Shapin and Schaffer's Leviathan (1985) thesis of the reduction of scientific problems to matters of fact and the social reproduction of experience. Another model of science emerged in the eighteenth century, notably through Linnaean systematics, which focused not on scientific facts but on naturalia – natural objects and organisms. Systematics was concerned with the determination, hierarchization, and formalization of information about naturalia – a series of problems that boiled down to reflecting and controlling scientific language. There one can synthesize this trend to dealing with matters of language. Using the microhistorical example of Lazzaro Spallanzani's position on Linneism, we show how matters of facts and matters of language are the two poles––dissociated in the eighteenth century––of an axis structuring the natural sciences.