Concerned to place physics on a stable footing at a time of great theoretical change, Russell argues that the concept of matter itself can be replaced by a logical construction whose basic foundations are events. He is careful to point out that this does not prove that matter does not exist, but it does show that physicists can get on with their work without assuming that matter does exist. Russell argues that fundamental bits of ''matter'', such as electrons and protons, are simply groups of events connected in a certain way and their properties are all that are required for physics. This Routledge Classics edition includes the 1992 Introduction by John G. Slater.