In architecture, composition refers to the conception of a building according to principles of regularity and hierarchy, or according to the principles of obtaining equilibrium. However, it is not until the beginning of the nineteenth century that the notion of composition becomes truly associated with architectural conception, notably under the influence of Jean-Nicolas-Louis Durand and his statement on the Marche à suivre dans la composition d’un project quelconque [Procedure to be followed in the composition of any project]. The concept quickly erodes during the twentieth century, with the adoption of neutral architectural devices, the use of aggregative processes, and the adoption of “objective” operations, all of which can be under- stood as an attempt to move beyond compositional principles. In Composition, Non-Composition, Jacques Lucan invites his readers to consider this novel historical perspective of architectural theory. The author describes the interaction of ideas that often clash with one another, with some that fade away as others emerge, thus offering invaluable keys to understanding contemporary architecture. Although this book is primarily addressed to students of architecture, it will also appeal to architects, historians of architecture, as well as to the interested public.