The article explores the thoughts of the German philosopher and sociologist Jürgen Habermas by emphasizing his communicative action theory. The article first explores his communicative action theory by discussing his distinctive social rationalization and dualistic conceptualization of modern society as comprising both a life-world and a system. After discussing Habermas's reconceptualization of modern society as comprising a distinguishable life-world and system, the article then directs attention to the function of law or a legal system in his unique reconceptualization of modern society. When discussing the function of law or a legal system, the article discusses the issues of juridification processes, legal validity and legitimacy of law. While doing so the article also addresses modern problems of social order and modern forms of cultural and social disarray. The article concludes by summarizing the discussion of the function of law or a legal system in light of Habermas's democratic theory, which is the source of his normative statement of legitimate law. All of this eventually allows for the presentation of certain conclusions about the function of law in modern society.