The main aim of this research is to relate the theory of ISD discussed in Hirschheim’s and Klein’s article ”Four Paradigms of Information Systems Development” (ISD) to Churchman’s theory of ISD discussed in his book ”The Design of Inquiring Systems”. It has been important to relate those two assumptions of ISD in order to enhance both of them and to get a more explicit understanding of ISD. The main hypothesis in this research has been that it is possible to relate them to each other and to clarify and enhance them since they are both based on philosophical assumptions of knowledge generation i.e. epistemology. Epistemological and ontological aspects of knowledge generation and nature of societies are very important for understanding of IS since knowledge transfer is more and more common because of ICT development. The synthesis of those two well-known approaches to ISD is the main contribution of this research master thesis. The other contributions are the solution for double-loop learning through multi-agent system development and the solution for developing sustainable network societies through peer-to-peer networking combined with centralised networking functioning as a library. I also have given an explicit explanation of the differences between monism (holism) and pluralism, in this case regarding to Leibniz’s and Locke’s philosophical views. Singerian epistemology has been generated from his explanation of insufficiency of either rationalist or interpretative approaches for explanation of natural laws and this is also one of my contributions in this research. I also recommended a complementary use of the rationalist, empirical and interpretative research methodologies for research in theoretical, experimental, applied and social science fields. It has been also examined which methodologies are predominating at universities offering degrees in social informatics and it has appeared that on the most of universities offering degree in social informatics, proper research methodologies for studying societies are used what had been expected.