Walter Benjamin, The Work of Art in the Age of Mechanical Reproduction (1936)

What happened was: when, with the advent of the first truly revolutionary means of reproduction, namely photography (simultaneously with the dawn of Socialism), art felt a crisis approaching that after a further century became unmistakable, it reacted with the theory of ‘l’art pour l’art’, which constitutes a theology of art. From it there proceeded, in the further course of events, almost a negative theology in the form of the idea of a ‘pure’ art that rejected not only any kind of social function but also any prompting by an actual subject. (In poetry, Mallarmé was the first to reach this position.)