This essay answers a single question: what was Robert Hooke, the Royal Society's curator of experiments, doing in his well-known 1665 work, Micrographia? Hooke was articulating a “universal cure of the mind” capable of bringing about a “reformation in Philosophy,” a change in philosophy's interpretive practices and organization. The work explicated the interpretive and political foundations for a community of optical instrument users coextensive with the struggling Royal Society. Standard observational practices would overcome the problem of using nonstandard instruments, while inherent in representation – the interpretive practice championed in the text – were important theological and political meanings. Hooke's kind of experimental philosophy undermined the claims made by “atheists” and “enthusiasts” – the enemies of the restored church and state – while also producing useful knowledge. Equally important, Hooke modeled the community described in Micrographia upon the classical res publica, but his community made important concessions to Restoration political realities, especially the growing role of commercial or transactional relationships.