Most loyal theatregoers tried to dismiss [The Birthday Party (1958)], but it wouldn't go away. You could say that the world of the play was unreal, but it was insistently analogous with the real world. What was missing from the plot was a clear motive, and, in a country dominated for two hundred years by the novel, motive had become a dramatic convention too. By ignoring, or at least obscuring, motive. Pinter concentrated his audience's attention on behaviour. The result is an uncomfortable diminution of human stature, and an equally uncomfortable analysis of human cruelty. (p. 21)

The lack of determinate values is a common feature of Pinter's plays. His characters flounder among approximations and hopeless enquiries (has no one ever counted the question marks in Pinter?). Pinter's cruelly accurate observation of the dialogue that surrounds a moral vacuum conveys his horror of it. Ben's question in The Dumb Waiter...