Nostra Aetate inaugurated a new era of interreligious dialogue in the Catholic Church, but the theological foundation it provided for such dialogue is complex. This article traces two different heuristic trajectories: a universalist trajectory revealed in Nostra Aetate 1–2 and reflected in the work of Bernard Lonergan, and a particularist trajectory in Nostra Aetate 4 and the work of Gregory Baum. Once distinguished, these two trajectories reveal a fruitful tension at the heart of the church’s new engagement with other religious paths.