All authors engaged in the development of the theme of harmony and dialogue, despite all their originality, are united by the desire to better understand the complex relationships of cultures and to highlight a common basis for the dialogue of people. Building such a dialogue and understanding the path toward harmony in relationships touch on the topic of rationality one way or another. Usually, the contribution of rationalism and its main brainchild – science – to the development of civilization is associated with scientific and technological development. Indeed, the face of contemporary civilization – production, service, communications, living conditions, health care, etc. – is determined, first of all, by the means provided by science and technology. Equally important, though perhaps less obvious, is the influence of the idea of rationality and science on moral culture and even political culture. In this essay, an attempt is made to identify the main aspects of this influence and to briefly outline their content and prospects.