This project charts the arrival and development of the words “lonely” and “loneliness” in seventeenth- and eighteenth-century English language and literature, arguing that they contributed to the advent of affective and aesthetic modernity. Nobody called themselves “lonely” in the sixteenth century; just as seventeenth and eighteenth-century literature affected loneliness, loneliness affected it. Through readings of Shakespeare, Milton, Defoe, Pope, Cowper, Charlotte Smith and Wordsworth, I show how this novel emotion motivates a series of questions that the notion of mere physical solitariness had only approached, refocusing previous considerations of individualism, sociability, sympathy, interiority, perception and the relation between language and experience.