In the Formalities lecture series Robin Evans reviews aspects of composition with a view to finding out why those aspects are so often regarded as fundamental categories, and with a view also to showing how they interact with other kinds of phenomena. Artists such as Malevich, van Doesburg and Mondrian understood abstraction as the process by which modern art divested itself of its illustrative and mimetic elements in a progression towards a non-objective essence. Evans argues that this process was not one of reduction but of supplementation and exchange, replacing the pictorial with other elements such as colour and geometrical forms. Tracking abstraction from painting to mathematics he examines some of the concepts that arise - symbol, reference, augmentation, materiality, orientability, boundedness - and asks how they relate to architecture.