The question of multiple worlds or universes was intriguing to medieval philosophers. While their revered predecessor Aristotle denied such an outlandish possibility, they were emboldened by the clerical Condemnation of 1277, which prohibited teaching that God could not create plural worlds. With limited scientific instrumentation, these philosophers relied on logic and reason, as well as “thought experiments” and imagined scenarios, as they shook off the Aristotelian chains and pushed the frontiers of scientific imagination.