Photographs are often invoked as an aid to understanding and tolerance. In humanist jargon, the highest vocation of photography is to explain man to man. But photographs do not explain; they acknowledge. Robert Frank was only being honest when he declared that “to produce an authentic contemporary document, the visual impact should be such as will nullify explanation.” If photographs are messages, the message is both transparent and mysterious. “A photograph is a secret about a secret,” as Arbus observed. “The more it tells you the less you know.” Despite the illusion of giving understanding, what seeing through photographs really invites is an acquisitive relation to the world that nourishes aesthetic awareness and promotes emotional detachment.
— Susan Sontag, On Photography, 1977