This text considers the problem of visuality not through the study of art works and images, but by analyzing the historical construction of the observer. The author insists that the problems of vision are inseparable from the operation of social power and examines how, beginning in the 1820s, the observer became the site of new discourses and practices that situated vision within the body as a physiological event. In this context, he examines a range of diverse work in philosophy, in the empirical sciences, and in the elements of an emerging mass visual culture.