The chapter examines three ways in which the historical avant-garde attempted to cross the ‘threshold’ of the aesthetic exception. The very act of crossing expresses the avant-garde rebellion against both the exceptional status of art and the dispositif that maintained it, defining the avant-garde as a practice of crossing the paradoxical space of the aesthetic exception to unite art with its ‘excluded’ zones. It identifies three paradigmatic crossings. The first is Duchamp’s attempt to cancel the difference between the exceptional object of art and the everyday object via the readymade. The second opening is made onto the space of racialised alterity, via ‘primitivism’ in art. Primitivism is analysed as a radical aesthetic attitude that contests the space of the aesthetic exception by crossing the threshold of what art excludes as art. The essay traces the roots of primitivism through the curatorial critique of ethnography (Apollinaire and later Malraux), and then as an artistic intervention that demonstrates that the exceptionalism of Western art is no exception, but one aesthetic system among others. It draws on Souleymane Bachir Diagne’s reading of Picasso to show how primitivism constituted a ‘becoming African’ of modernist art. The third crossing is onto the space of ‘pathological’ artistic production through the discovery of outsider art, notably associated with Jean Dubuffet’s concept of Art Brut. The essay shows how each attempted crossing must reimpose the very thing it seeks to escape: the aesthetic exception.