The seventeenth-century microscopists Robert Hooke and Henry Power sought to rhetorically establish the truthfulness of the visual images produced by their instruments, but a counter-rhetoric of visuality was established by Margaret Cavendish in Observations upon Experimental Philosophy (1666). The microscopists’ belief that magnification revealed the truth of nature ran counter to Cavendish’s probabilistic belief that no individual could grasp the infinite truth of nature and sought explanations from the superficies of observed objects rather than the ‘interior figurative motions’ which Cavendish saw as the universal cause of all natural phenomena. While the microscopists emphasized the aesthetic beauty of the micro-visible world, Cavendish emphasized its monstrosity: for her the truth could only be perceived by the ‘natural’ eye observing things in their unmagnified state. Exploiting the microscopists’ complaints about the variability of their images and the defects of their instruments Cavendish redefines the microscopic image as definitively outside the ‘real’.