 Also, because hybrid accounts incorporate consequentialist and retributivist elements, they may be subject to some of the same objections raised against pure versions of consequentialism or retributivism. For example, insofar as they endorse retributivist constraints on punishment, they face the thorny problem of explaining the retributivist notion of desert (see s. 4 above): but it is not clear whether they can be justified without such an appeal to retributivist desert (see Hart 1968: 44–48; Feinberg 1988: 144–55; Walker 1991, ch. 11). Even if such side-constraints can be securely grounded, however, consequentialist theories of punishment face the broadly Kantian line of objection discussed earlier (s. 3), that punishing with the aim of serving some desirable social ends treats those punished merely as means to those further ends, which denies them the respect, the moral standing, that is their due as responsible agents.