Throughout this book, the slippery terms ‘avant-garde’ and ‘mainstream’ have been applied to publications and their producers to distinguish positions in the market that do not lend themselves to essentialist definitions, but can only be understood as pragmatically defining each other in mutual opposition. On the one side, selfdeclared rebel alliances of variable internal cohesion insist on their fundamental differences with a vested interest that jealously guards its dominance. The heterodox challengers associate this dominance with either commercialist vulgarity, or with academic neophobia. On the other side, an equally diverse array of orthodox established or aspirational producers employ the rhetoric of common sense and consecration through institutionalized authority to ward of challenges to the status quo.

In reality, however, there are countless overlaps between the two purportedly opposite positions, and many artists and authors do not consistently stick with either side. Most will affiliate themselves with both avant-garde and mainstream at various stages of their careers or for various aspects of their output, and representatives of either position can share publication contexts such as the same publisher's list, or the same periodical. The authors and artists of the 1890s, as we have noted time and again, were no exception. Nevertheless, from the first attempts to historicise the avant-garde position, or ‘vanguardism’ as it was termed by Renato Poggioli in the 1960s, the many schools within the Aesthetic Movement have been considered as not actually part of this wider phenomenon, but rather the culmination of its ‘prehistory’. In his much-debated reply to Poggioli, Peter Bürger too emphasised the indispensable role of Aestheticism as a precursor that heralded a phase in cultural history in which ‘the apartness from the praxis of life that had always constituted the institutional status of art in bourgeois society’ had become ‘the content of works’. This introduced the ‘self-criticism of art’ and its place in society maintained in this book as one of Aestheticism's most important characteristics, but that according to Bürger only fully developed in the early twentieth century. Both theorists denied Aestheticism its avant-garde status because they narrowed it down to the clichéd formula of ‘Art for Art's Sake’, which according to their shared Marxist perspective meant a lack of engagement with society.