Piotr Piotrowski’s vision of horizontal art history is a diagnosis of severe structural problems with modern West-centred art history writing. As a “model” for future use and a new “paradigm” of art historiography, however, the vocabulary and its generic avant-gardism threatens to short-circuit this critique. Part one of this chapter deals with how the notion of horizontal art history is presented and discussed by the author. Part two argues that to accomplish a truly horizontal or flat art history, we must change our inherited conceptual art-historical infrastructure, which is soaked in hierarchical thinking and binarisms. An “art history of the margins” is inevitably hierarchical vis-à-vis its external “centre” and internally—by differentiating between advanced and mediocre, cutting edge and reargarde, important and less important art, etcetera. The article suggests how Piotrowski’s project of an art history “without domination” could be realized. What I term lateral art studies seek to investigate how the material singularities of art, i.e. artworks, interconnect and relate to each other, what shifting assemblages (DeLanda) they produce, what time layers (Koselleck) they contain, and how such studies could overcome the compulsion among art historians to decide what is in and out, major or minor, central or marginal.