We were at first puzzled by Alexander Wendt's latest rejoinder, since systemic theorists need concede nothing in recognizing states as self-interested actors with identities and interests. They have only to add that these identities and interests are shaped by the system in general and are given specific direction at any one time by the systemic pressures operating in the previous period. After all, ‘self-interested’ is a dummy term, until supplied with content, and systemic theorists can regard the system as the source of what matters. Explanations which proceed ‘top-down’ by explaining the behaviour of the units in terms of the system need some kind of feed-back mechanism involving the units. It is no objection to systemic theory that the units contribute to the process, provided that they do so in ways shaped by the demands of the system. In short, why does Wendt believe that the identities and interests of actors cannot be formed by the system? Waltz certainly offers a powerful explanation cast in precisely these terms.