The paper discusses one of the major principles of critical rationalism with a critical approach. This principle is about giving all participants the opportunity to argue in a friendly spirit. I analyze the main theoretical and practical implications of this maxim and argue for the importance of this Popperian principle beyond scientific rationality, enabling a general rationality for co-operation among all interested parties in the argumentation of scientific or everyday life issues, no matter if they are our friends or opponents. The conclusion is that this maxim has an inner logic with an effective result of successful dialectic argumentation and critical thinking. A parallel has been drawn between Christian love for others, the Socratic insight that it is better to suffer injustice than to do it and the strategy of Popper’s principle. And hereby I suggest its compati-bility with Popper’s so-called via negativa.