 That said, note that there are important differences between the ways in which Zalta, on the one hand, and Castañeda and Rapaport, on the other, formulate these distinctions. For Zalta (1983: 12), encoding is a primitive notion which he embeds in a rigorous higher-order modal theory that is then used to prove the existence, and derive the properties, of abstract objects, including fictional objects. For both Castañeda (1989: 200) and Rapaport (1978: 162), on the other hand, internal predication applies to set-correlates, and so this mode of predication can be defined in terms of set-membership: a (fictional) entity F has P internally (or: has P as a constituent) if and only if P belongs to the property set that is correlated with F.