This paper elucidates the structure and scope of Pynchon’s temporal imagination by studying the complex relations between narrative time and modality in his 1997 novel Mason & Dixon using the conceptual framework of contemporary narratology. It argues that Pynchon’s use of the subjunctive mode allows him not only to articulate the political and ideological concerns in his vision of America on the eve of its founding but also to address the problems of historicity, causality and irreversibility of time. By employing the subjunctive as a general narrative strategy, Mason & Dixon challenges the various temporal regimes and discourses of modernity, and projects imaginative re-figurations of time and space. In carrying this out, the novel moves beyond what Pynchon calls “the network of ordinary latitude and longitude” (Against the Day 250) and replaces a totalizing singularity with plurality of times and timescapes.