A standard way of praising machines in the long eighteenth century was to say they were ‘simple’. I argue that recovering discourses around mechanical simplicity reopens questions of the significance of machines and the relations between innovation and use: this qualifies the singular ‘meaning for machines’ for which Larry Stewart has argued during this period (Larry Stewart, “A Meaning for Machines: Modernity, Utility, and the Eighteenth‐Century British Public” The Journal of Modern History , Vol. 70, No. 2 (June 1998), pp. 259-294.”) This history of machines encompasses ventilators, agricultural tools, safety equipment, and hand-mills, as well as steam-engines, waterwheels and scientific instruments. It helps to make sense of the otherwise puzzling fact, observed by Musson and Robinson, that Stephen Hales’ ventilators were the most heavily advertised machines of the eighteenth century. (Albert Musson and Eric Robinson, Science and Technology in the Industrial Revolution (Manchester: Manchester University Press, 1969), pps 378-9, 384-7.)Mechanical simplicity during this period involved a cluster of interrelated senses, all of which were significant for their evaluation within working worlds during this period. These senses included: openness to scrutiny, freedom from friction, analogical connection to natural processes, partaking in divisions of labour, and adaptability in multiple circumstances. The primary archive for my analysis is the premium awards made by the Society for the Encouragement of Arts, Manufactures, and Commerce – a London-based economic society founded in 1754, which offered small inducements and supported numerous simple machines. I have two goals: to give a picture of significant aspects eighteenth century mechanical culture embedded in its own local context rather than answerable to an unknown future; and to explain how a particular vision of public life, represented by the Society, led to the valuing of these particular devices.