This is an analytical investigation of the music of Beethoven's third period, from the 'Hammerklavier' to the late quartets. The analysis reflects a variety of approaches without adhering to any one particular technique. Nevertheless, it advocates a single theory: that this music is essentially disunified while keeping within the framework of the Classical style. Insofar as Classicism denotes equilibrium, symmetry and closure, Beethoven's late style pushes its rules to breaking-point while, paradoxically, preserving them. Each chapter explores Beethoven's critique of the Classical Style from a different angle. Chapter 1 outlines the historical and philosophical background to organicist notions of musical unity, offering an alternative anti-organicist theory based on Bergson's ideas of comedy. Chapter 2 distinguishes the `paradoxical' style of Beethoven's late period from the styles of his early and middle periods, concentrating on sonata form. Chapter 3 looks at formal problems in three string quartets. Chapter 4 considers the difference between sections within movements and movements within pieces, and how Beethoven challenges this distinction. Chapter 5 reveals the subtle formal processes within three variation movements. Chapter 6 shows how Beethoven redefines the nature of counterpoint. Chapter 7 investigates cyclic unity across entire compositions, focusing on the way the significance of a piece can be transformed by its finale.