This chapter focuses on the way madness as a topic is explored both in King Lear and in a wide range of readings of the play by psychiatrists and psychologically inclined critics. The chapter excavates the unspoken assumptions that underpin these readings in order to illuminate changing attitudes and changing definitions of madness and the mind across time and place. The chapter examines in detail the language used in the play and in critical readings of it, analyzing the implications of recurring patterns of images of fluidity and solidity in describing the mind. The chapter then turns to a number of case studies, focusing on a range of twentieth-century psychiatrists’ readings of the play to establish in more detail the implications of the crossover between psychiatry and literary criticism. The chapter then historicizes both the development of modern psychology and the accompanying readings of the play, placing both within a longer history of paradigm shifts, in order to argue that the play demonstrates and enables the layering and intermingling of paradigms. The chapter suggests that both in psychiatry and in literary studies, openness to pluralism is needed to appreciate the fuller range of meaning enabled by these multiple epistemologies.