Daily communication today is predominantly digital, but contemporary novels continue to be interested in paper letters. Why? What do letters, written on paper, offer to the novel in the twenty-first century? This essay explores the material letter's contemporary value as metaphor, reading as a case study Ian McEwan's The Children Act. McEwan's novel dramatizes a conflict between religion and the secular law, which is an example of the type of dispute that Jean-François Lyotard identifies in The Differend: a dispute that is unresolvable because the process for regulating it is unable to register the wrong that one side suffers. In their different modes, these two texts consider intractable conflict and the ethics of its regulation, the workings of which are analyzed here through the suggestive correspondences between the dynamics of Lyotard's differend and those of letters. These correspondences derive, this essay argues, from the letter's material properties, which underlie its ability to function as metaphor. The letter's temporal structure of delay and the silences and instability that delay produces, in particular, have productive affinities with the workings of the differend. These correspondences help to delineate the conflicts of The Children Act and to reveal the value of the letter as metaphor more generally. This case study presents an example of the letter as a metaphorical resource, whose possibilities are distinct from those of digital communications and whose flexibility and nuance help to account for contemporary novels' continued interest in the letter.