 Alexander presents a metaphysical argument for the unity of space and time, arguing they are merely distinguishable aspects of Motion. He argues that space and time must be unified because, when abstracted away from each other, it becomes clear that they could not exist independently. Time would become a mere “now”, incapable of succession; and space would become a mere “blank”, without distinguishable elements (Alexander 1920i: 47). Motion is both successive and boasts distinguishable elements - this is because it is the union of space and time. Alexander’s metaphysical argument for this union was severely criticised by  Broad (1921a,b).[2]  Alexander considered his account of spacetime to be in line with the physics of his day. The following might be understood as an argument from physics for his position: