What is Architectural History? is organized by five chapters. The first positions modern, academic architectural history (the architectural history of Wölfflin, Gurlitt, Riegl and their contemporaries) as a disciplinary inheritance of four traditions for knowing architecture as a past field. These are the presentation of architectural history in the architectural treatise, as part of the architect’s historical and technical patrimony; of the architect as an artist in history, in the biographical tradition consolidated by Vasari; of architecture as a fact of the past available for empirical study; and of architecture as part of culture, and therefore subject to the early study of cultural history. Of these, cultural history (or the cultural sciences) has arguably played a strong role in establishing the field’s disciplinarity. Chapter two lays out a series of methods—soft methods—by which historians organize past time and relate it to the present: as a succession of styles, governed to a greater or lesser degree by concurrent historical events; as a succession of architects, subject to processes of influence and transferral; according to geo-political boundaries, recognizing that the historian can often find coherence in a field bounded by a political border or held together by a shared language; by type, comparing like with like in order to understand processes of change within comparable buildings; as a technique, finding a history in the arguably irreducible concerns of (what we can now call) architecture over a long period of time (planning, spatial formation, shelter, etc); and theme and analogy, where architecture can be held to index concerns that are not architecture’s own (or, which in turn help shape architecture as a field). The next chapter draws upon a series of cases to consider the relation between forms of evidence and the kinds of architectural history they allow. It suggests that evidence can be procedural, contextual or conceptual in nature, each kind of evidence serving the historical subject to specific ends: from tying up loose ends in established knowledge to defining architecture historically on new grounds. Chapter four returns to the question of actuality, asking how involved architectural historians should be in the world of architectural practice. It sets up a conversation between three architectural historians of note—Zevi, Millon and Tafuri—to tease out a series of positions on this question, which are in turn informed by Croce, whose influence over the Italian discussion on this issue has been immense. The final chapter speculates on the impact of the ‘theory moment’ on the shape and possibilities of architectural historiography in the present moment, tracing some developments that would seem to have decisively informed the outer limits of the field, its content, and the objectives of its scholars. I would be a fool to imagine this as a definitive answer to the question What is Architectural History?, and indeed I look forward to learning from the debate that my own views will provoke.