Habermas, director of the Max Planck Institute in West Germany, stands alone today in his ability to synthesize a staggeringly wide range of social and scientific theory, from different and often antagonistic schools, into one all-encompassing social theory in the grand tradition. Only Habermas, it seems, can bring logical-positivism, neo-Marxism, and hermeneutics together; only he can converse freely with Popper, Piaget, and Adorno. The main result has been Habermas' theory of communicative action, presented before but now thoroughly fleshed out. (This first volume was published in Germany in 1981; the second is still to come.) Habermas' view is that all action involves meaning: to act, in the strict sense of doing something, involves an instrumentality (i.e., the action is for the purpose of achieving an individual aim), but it presupposes an agreement with other actors about the meaning of the act. In order for an act to be meaningful, there has to be a whole area of shared meanings about the world of objects and society: the ""lifeworld."" Speech acts, on the other hand, are made with the direct purpose of establishing meaning, of being understood. So language involves the use of reason. From these bases, Habermas wants to work out a theory that will combine an explanation of the structural development of language (in the manner of Chomsky or Piaget among linguistic structuralists, or Carnap and Peirce among philosophers) and an understanding of the historical constitution of the lifeworld (in the mode of the anthropologists, or theorists of history like Marx). Another way of posing Habermas' project: he is looking for one theoretical way of understanding society from, simultaneously, the point of view of the participant, who shares its unstated and stated meanings, and that of the observer, who stands outside and therefore sees the historical or environmental constraints hidden to the participant. Habermas' first volume lays all this out; in its second half, he also begins to explore social theory since Max Weber, both to take up the actual problems the theorists addressed (such as the development of law or technology) and to demonstrate that this theory of communicative action can be applied to them. The volume ends with nco-Marxist theories of reason; the next, a table of contents indicates, will move to the lifeworld arena (Durkheim, etc.) and complete Habermas' general theory of modernity. Here, Habermas undertakes to show that Weber's theory of rationality cannot account for influences impinging from outside reason's ken (and also to dispatch those who followed Weber while criticizing him). As usual, Habermas' procedures and arguments are laced with technical issues, and highly sophisticated. His Communication and the Evolution of Society (1979) will suffice for an introduction. But for the serious student, this is the impressive proof of Habermas' accomplishment.