This chapter examines how the late seventeenth-century British philosophy of sensation, feeling, and selfhood responded to the challenges of mechanism with the idiom of the insensible. It shows how this idiom carries forward from John Locke and Robert Boyle to philosophers of the mid-eighteenth century, the age of sensibility, who use it to address a variety of problems. The consistent, Lockean element in these usages by David Hartley, Étienne Bonnet de Condillac and David Hume, Eliza Haywood and Adam Smith, is that they do not refer to mental contents. One does not hear of “insensible perceptions.” There are no “unconscious thoughts” or “unfelt sensations” in the British tradition surveyed here. Writers in this tradition rather describe insensible powers that affect the mind without themselves being mental. They are nonconscious, not unconscious. This is an implication carried by the idiom into articulations of quite a wide variety of other ideas. All of them indicate the persistent usefulness in philosophies of feeling of a stylistic gesture toward something beyond the reach of both feeling and philosophy.
Demons of the mind: satanic thoughts in seventeenth-century England