In reference to commentaries on the paper (Mammen and Mironenko, Integrative Psychological and Behavioral Science 49(4):681–713, 2015) some clarifications are introduced concerning the general landmarks and objectives in the development of psychological science, in respect to which activity theories (AT) can be assessed and evaluated. Contemporary psychological science is developing along the path of integration, as part of the emerging global world. AT has some special value and importance in this respect. It can contribute to the development of the emerging multi-paradigmatic system of the global psychological science because it combines two aspirations, which are rarely combined in psychological theories: a) consistent focus on scientific method, objectivity and conclusiveness; b) the pursuit of a holistic and complete, not simplified and not one-sided comprehension of the subject. The former provides good bases for dialogue with “objective” psychological approaches, close to natural sciences. The latter is suggesting dialogue with teleological humanitarian psychologies. Therefore, AT can engage in networking with a wide range of theories, facilitating the integration of psychological knowledge. It can contribute to resolve the much discussed collision of reductionist “scientific” theoretical models and loose “comprehensive” descriptions in contemporary psychological science. Developing dialogue and cooperation with other schools is of special importance for the RAT, which should return to the international science, where it was rooted, overcoming the language and conceptual barriers. Some new considerations are suggested regarding the theory of the two types of categories of Jens Mammen.