One of Roy Bhaskar's central ontological claims is that in addition to the actual - the things and events that occur in the material universe - our ontology must also recognise a domain of the real, which includes the actual, but extends beyond it. In his first book, A Realist Theory of Science, he argued that the non-actual includes real causal powers, a very strong argument that I explained towards the end of my last blog post. However, if we accept this argument this opens up rather a large question: what else could be real but not actual? This is a crucial question for materialist realists, because it provides a door through which non-material stuff could reappear in our ontology, and we only want to open that door rather carefully! This post suggests one way of thinking about what sorts of stuff should be admitted.