Philosophy does make progress. The achievement of philosophers of space and time over the past 30 years has been extraordinarily important and far-reaching. The dramatic claims made by Einstein and many other physicists about the death of Newton's absolute space have been rebutted. The nature of spacetime has been substantially clarified in ways that would have astonished the pioneers.

This success is all the more significant because it has taken place in the face of hostility from many physicists. Even today, many or most physicists cling to some of the naive early claims made about relativity theory, which survive as a kind of folklore in the physics community. There are exceptional physicists who contributed to recent developments. But philosophers deserve recognition for penetrating through the fog that surrounded the foundations of spacetime theories and for moving the debate ahead.

Ancient and medieval philosophers debated the existence of universals. Was there, they asked, a single, universal “form of red” present in each red thing and somehow making it red? Realists argued that such universals were needed to explain the similarities between colours and all the properties we see around us. Tough-minded nominalists insisted that universals were merely common names, and resisted entities that were not solid, respectable individuals. The controversies below provide a modern parallel to these debates. One side accepts invisible spatial structures to make sense of what we see; the other derides this as extravagant metaphysics and adheres closely to concrete observables.