The outstanding representative of the post-war generation of Frankfurt School social theorists, Habermas has gained a growing international reputation for his attempt to reconceptualize the basic categories of critical theory beginning with Marx--even though his work is abstruse enough to be virtually inaccessible to the lay reader. Best known here for Knowledge and Human Interests (1972)--a critique of modern empiricism--Habermas has recently occupied the center stage within the Federal Republic itself, in a prolonged Methodenstreit with the various positivist and technocratic currents in German sociology which share a common descent from Max Weber. Legitimation Crisis is conceived against this polemical background. Arguing that neither systems theory nor orthodox Marxism can give adequate expression to the particular ""crisis logic"" of advanced capitalism, Habermas proposes the central notion of ""legitimation deficit""--the unmasking of power relations occasioned by the collapse of the basic bourgeois ideology of fair exchange. While in agreement with the classical Frankfurt principle that unbridled technological expansion has transformed ""reason"" into a pragmatic ""instrumental rationality,"" Habermas shares little of the pessimistic resignation of the late Horkheimer and Adorno. Seeing instead a growing human potentiality for self-reflection in ""collective rational discourse,"" he points the way toward a liberating political praxis grounded in mass participation and ""consensual will-formation""--a message that has influenced New Left theoreticians here as well as abroad. A substantial addition to what is already a major achievement. For specialists only.