 Sydney Shoemaker (2007, chapter 2) defines a related notion of property realization, which he calls the ‘subset view of realization’. He says that “as a first approximation, property P has property Q as a realizer just in case (1) the forward-looking causal features of property P are a subset of the forward-looking causal features of property Q, and (2) the backward-looking causal features of P have as a subset the backward-looking features of Q” (2007, 12). Once again, if P has more than one realizer, then P is multiply realizable.