This paper addresses the question of visual communication in early modern learned journals. Paradoxically, the case analysed to explore this question concerns an image that never existed. In 1694 and 1703, the French naturalist Charles Plumier (1646-1704) published two articles on the American cochineal. One of the most valuable products in Transatlantic trade, the cochineal was still the object of debate by European naturalists, who were undecided whether it was an insect or the seed of a plant. With these two articles, Plumier entered into, for the first and the last time, a public scientific controversy. As a result of his observations with the microscope, he became convinced of the animal nature of the cochineal, yet he did not use any kind of picture to support this claim in his articles. The lack of any kind of visual argument is especially striking in the case of a naturalist whose notes include around three hundred drawings, and whose printed works were mainly composed by engravings. The question is thus why a scholar like Plumier, who observed and conceptualised nature through the practice of drawing, did not use images to support his claims in the context of a public debate such as that over the nature of the cochineal.

I will use this example to consider the ambiguous status of the visual in scientific controversies: while eyes were useful for understanding nature in a private sense, images do not seem to have been viewed as reliable evidence in a public debate. The paper attempts to explore, by means of this case study, the particular functions with which images were endowed in the public sphere, and to examine these in the context of the world of learned journals. My aim is to explore the ambiguity of the visual in the early modern period, as well as the uncertainties naturalists had to face when trying to construct a reliable account of nature.