The idea of rational understanding lays very close to the heart of Professor Janusz Kuczynski, an advocate of universalism as well as dialogue between diverse philosophical schools and worldviews, and doctoral advisor to the present paper’s author. This idea’s theoretical conceptualisation—a conceptualisation that has proven to be convincing and adequate to the conditions of the modern world—was developed by Professor Jürgen Habermas, whose ideas and theories were also the subject of a doctoral thesis written by this paper’s author in the latter half of the 1970s under Professor Kuczynski’s tutelage. The author shares some grateful memories of his doctoral tutor, and also sets his one-time attempts to apply the theory of communicative action to two experiences of the real socialism era in Poland (the events of 1980/1981 and 1989) against his efforts to analyse contemporary Polish realities through the prism of the communicative rationality conception. This comparison shows that the application of a conception of rationality funded by communicative action to the turbulent transformations under real socialism was to a certain extent naïve—though not devoid of critical significance—and also reveals the preconditions (in the sphere of understanding oneself and the world) for the implementation of the rules of communicative rationality in social and political reality. The paper is in part dedicated to the memory of Professor Kuczynski, therefore it contains a somewhat extensive account of the circumstances which led the author to study the thought of Habermas under Kuczynski’s tutelage, as well as the consequences of this choice, which proved of considerable significance for his further life. However, the main themes are, first, the validity (and naivety) of applying a conception of rationality funded by communicative action to two significant experiences of the real socialism era, and, secondly, the need—revealed by diagnosing contemporary Polish reality with the help of the communicative rationality conception—for certain preconditions enabling the implementation of this type of rationality in social and political reality. One such precondition is the transition of sufficiently broad parts of society from thinking in terms of worldviews (Weltaunschauungen) to post-metaphysical thinking in terms of the “lifeworld” (Lebenswelt). Keywords: Rational society, communicative action, communicative rationality, “Solidarnoss” [Solidarity], Jürgen Habermas, Janusz Kuczynski.