The matter concept has had an extraordinarily complex history, dating back to the earliest days of the sort of reflective thought that came to be called ‘philosophy’. History here, as elsewhere, offers a valuable means of understanding the present, so it is with history that I will be concerned – history necessarily compressed into simplified outline.

This story, like that of Caesar's Gaul, falls readily into three parts. First is the gradual emergence in early Greek thought of a factor indispensable to the discussion of the changing world and the progressive elaboration of that factor (or, more exactly, cluster of factors) as philosophic reflection deepened and divided. Second is the radical shift that occurred in the seventeenth century as the concept of matter took on new meanings, gave its name to the emerging philosophy of materialism and yielded place to a derivative concept, mass, in the fast-developing new science of mechanics. Third is the further transformation of the concept in the twentieth century in the light of the dramatic changes brought about by the three radically new theories in physics: relativity, quantum mechanics, and expanding-universe cosmology, with which that century will always be associated. Matter began to be dematerialized, as it were, as matter and energy were brought into some sort of equivalence, and the imagination-friendly particles of the earlier mechanics yielded way to the ghostly realities of quantum theory that are neither here nor there.