Problem-based learning (PBL) is an innovative educational approach that dates back to the 1960s. However, the twenty-first century goal of sustainable education poses a challenge to PBL, especially as it relates to isolation. Here we discuss the underlying issue of isolation in three respects. First, the information-processing model of PBL depends on generalized skills, whereas real life problem-solving skills involve context-bound cognitive processes. Second, in all models of PBL, the focus on knowledge acquisition for a specific problem improves performance but separates education from the world at large. Third, the existing culture of measurement strengthens the aforementioned isolating effects. In response, we introduce a conceptual approach based on Hannah Arendt's technical notion of 'world'. We make suggestions to meet the criteria of sustainable education by reconnecting PBL to our shared world, and emphasizing a responsibility for this shared world.