Among distinguished sociologists. The main theme of Habermas' theory is that valid knowledge can only emerge from a situation of open, free and uninterrupted dialogue. In Towards a Rational Society and Theory and Practice he argued that the idea of a neutral apolitical science, based on a rigid separation of facts and values, is untenable since questions of truth are inextricably bound up with the political problems of freedom to communicate and to exchange ideas. He has been a prominent critic of positivism and economic determinism in Knowledge and Human Interests.
Habermas has also been highly critical of systems theory, engaging in a prolonged debate with N. Luhmann in Theorie der Gessellschaft oder Sozialtechnologie? He has been influential in recent studies of the state and the decline of normative legitimacy in Legitimation Crisis. Communication and the Evolution of Society was concerned with problems of power and legitimacy. In The Theory of Communicafive Action he criticized Western social theory for its failure to avoid reductionism and to develop a valid theory of communication and rationality. In his recent work he has criticized post-modernism in The Philosophical Discourse of Modernity.