In the age of post-digital architecture and digital materiality, This Thing Called Theory explores current practices of architectural theory, their critical and productive role. The book is organized in sections which explore theory as an open issue in architecture, as it relates to and borrows from other disciplines, thus opening up architecture itself and showing how architecture is inextricably connected to other social and theoretical practices. The sections move gradually from the specifics of architectural thought – its history, theory, and criticism – and their ongoing relation with philosophy, to the critical positions formulated through architecture’s specific forms of expression, and onto more recent forms of architecture’s engagement and self-definition. The book’s thematic sessions are concluded by and interspersed with a series of shorter critical position texts, which, together, propose a new vision of the contemporary role of theory in architecture. What emerges, overall, is a critical and productive role for theory in architecture today: theory as a proposition, theory as task and as a ‘risk’ of architecture.