Abstract

Discourse ethics is originally conceived as a programme of philosophical justification of morality. This depends on the formal derivation of the moral principle (U) from non-moral principles. The moral theory is supposed to fall out of a pragmatic theory of meaning. The original programme plays a central role in Habermas's social theory: the moral theory, if true, provides good evidence for the more general theory of modernization. But neither Habermas nor his followers have succeeded in providing a formal derivation. This essay shows how and why Habermas's proposed derivation is impossible. As if aware of the lacuna, Habermas has recently suggested that (U) can be derived by 'abduction' rather than deduction. The proposal draws heavily on modernization theory; hence the only justification for (U) now available to him rests on premises drawn from that theory. The original programme of the justification of morality has thus given way to the weaker programme of the philosophical elucidation of morality. Further, since Habermas's moral theory is no longer justified independently of modernization theory, but at least partly by it, the moral theory cannot without circularity provide evidence for the modernization theory.