An accidental glance at a newspaper notice causes Rousseau to collapse under the force of a vision. A car accidentally hits Giacometti, and he experiences an epiphany. Darwin introduces accident to the basic process of life, and Freud looks to accident as the expression of unconscious desire. Accident, Ross Hamilton claims, is the force that makes us modern. Tracing the story of accident from Aristotle to Buster Keaton and beyond, Hamilton's daring book revives the tradition of the grand history of ideas. Accident tells an original history of Western thought from the perspective of Aristotle's remarkably durable categories of accident and substance. Throughout antiquity and the Middle Ages, Aristotle's distinction underwrote an insistence on order and subordination of the inessential. In a groundbreaking innovation, Hamilton argues that after the Reformation, the concept of accident began to change places with that of substance: accident became a life-transforming event and effectively a person's essence. For moderns, it is the accidental, seemingly trivial moments of consciousness that, like Wordsworth's ''spots of time,'' create constellations of meaning in our lives. Touching on a broad array of images and texts - Augustine, Dante, the frescoes of Raphael, Descartes, Jane Austen, the work of the surrealists, and twentieth-century cinema - Hamilton provides a new way to map the mutations of personal identity and subjectivity.