What would modernist fiction look like if it were mindless and had no access to mental states? While modernism is often understood as a psychological turn inward, this article shows how introspective psychology competed against other psychological discourses—and how writers such as Samuel Beckett theorized a modernism without introspection. In his essays “Dante … Bruno … Vico … Joyce” (1929) and Proust (1930), Beckett argued that the psychological interiority of high modernist fiction could be attributed to nonmental and behavioristic causes. And in his novel Murphy (1936), he suggested that novelistic form belied the unknowability of mental states. To Beckett, the novel's ability to know other minds was itself fictional; the representation of character minds, he contended, should be subjected to the same psychological laws as real people. Beckett's early writings, then, ask us to reconsider how we understand literature's historical and logical relationship to psychology. Following Beckett's lead, this article concludes by asking us to imagine what the modernist novel—as well as contemporary criticism—would look like if we stopped taking the introspective mind for granted.