This chapter provides an overview of the novel of ideas that contrasts the form with Henry James’s modernist conception of the art novel. Ian McEwan writes exemplary novels of ideas insofar as his works incorporate political, philosophical and above all scientific ideas even as they develop formal, stylistic and aesthetic complexity. After discussing Or Shall We Die? and The Ploughman’s Lunch, the chapter examines four novels: Black Dogs, Enduring Love, Saturday and particularly The Child in Time. McEwan’s novels of ideas consistently explore and demonstrate unexpected capabilities of the genre. They unfold the drama and texture of their ideational content, from the level of plot device and set piece down to that of lexical units. Ideas animate but never overwhelm aesthetics. McEwan’s novels of ideas explore the capacities and capabilities of scientific inquiry and literary representation even as they ultimately reveal the limits of both.