The concept of space was born in paradox and seemed to have the flimsiest claim to existence. Although nothing but mere empty extendedness, it helped make motion and change understandable. Aristotle's rugged common sense rejected “space” out of hand, and made do with his plenum of concrete objects. We have now seen that this ancient debate was preparation for the grander controversies over Newton and Einstein's concepts of space. Like the ancient atomists, Newton embraced space to make sense of motion. His law of inertia demanded a world of geometric lines, and the sloshing water in his bucket seemed to make absolute space almost visible. Like Aristotle, the tough-minded empiricists made war on this metaphysical extravagance. Mach, Einstein and contemporary relationalists all fought back against a space existing over and above its contents. Against Newton and Lorentz, they dispensed with “superfluous” structure and pushed physics back down towards concrete objects and their concrete relations.

But now the folklore that surrounds Einstein's relativity theory has been dispersed. Amid Einstein's many triumphs, he did transform and deepen the concept of space. He did not, however, reduce space to its contents. This flimsy nothing has proved resilient. In special relativity, we saw that the defence of absolute space in Lorentz's minority interpretation was not ruled out by experiment. Furthermore, it provided attractive explanations where the mainstream provided none. A philosopher would say that the case for eliminating absolute space there rested on a strict empiricist ideology, and was not compulsory.