On Photography began with a single essay in which Susan Sontag wanted to explore some of the problems, both aesthetic and moral, presented by the omnipresence of photographed images in her culture. As the essay became more complex and historically expansive, it suggested others, and over five years Sontag eventually wrote a series of essays in which she traced the traditions and meaning of photography. As she later was to write, the argument sketched in the first essay evolved full circle through digressions and documentation into the more theoretical last essay, where the collection ended.
As a result, Sontag—along with such other literary culture critics as Roland Barthes, John Berger, Walter Benjamin, and Marshall McLuhan—helped to rewrite the ways in which people see the role of photography in modern society. For her, the term “modernism,” with its ahistorical tendencies, has distorted and disguised both the social uses and the nature of photography, obscuring from the photographer and viewer alike the propagandistic and exploitive nature of the medium, especially under capitalism. Sontag has always defined social criticism as an active, not a passive, occupation. Her role in essays such as those contained in On Photography is to evaluate the place of the medium in the human experience and, in the process of discussing that place, to explain the influence of photography and the photograph, making clear those elements of the medium that have traditionally been diverted by formalist/aesthetic approaches.