Super-substantivalism is the thesis that space is identical to matter; it is currently under discussion ? see Sklar (1977, 221?4), Earman (1989, 115?6) and Schaffer (2009) ? in contemporary philosophy of physics and metaphysics. Given this current interest, it is worth investigating the thesis in the history of philosophy. This paper examines the super-substantivalism of Samuel Alexander, an early twentieth century metaphysician primarily associated with (the movement now known as) British Emergentism. Alexander argues that spacetime is ontologically fundamental and it (...) gives rise to an ontological hierarchy of emergence, involving novel properties such as matter, life and mind. Alexander's super-substantivalism is interesting not just because of its historical importance but also because Alexander unusually attempts to explain why spacetime is identical to matter. This paper carefully unpacks that explanation and shows how Alexander is best read as conceiving of spacetime as a Spinozistic substance, worked upon by evolution. (shrink)