This paper is an exploration of the relevance of Habermas's social theory for understanding meaning making in the context of shared online interaction. It describes some of the key ideas within Habermas's work, noting the central importance it gives to the idea of communicative action - a special kind of discourse in which there is "no other force than that of the better argument" and no other motive other than "the cooperative search for truth". The paper then turns to the referencing of Habermas by educationalists in general and by supporters of online discussion in particular. It argues that a Habermasian perspective on meaning making is one in which participants strive for "genuine consensus" by interrogating their own beliefs while actively engaging with opposing points of view. The value of this approach is that it introduces a concern for validity or truth into discussion of knowledge building and discriminates between emancipatory and strategic goals. While critics would argue that genuine consensus is not achievable, from Habermas we can better understand the importance of striving for such consensus.