The fundamental task of western theology is to provide an answer to the question how the major themes of christian faith can be made more relevant to present and future generations. One of the most important problems is whether modern theology can adequately connect to the daily life of people and groups. Until now, it has failed to provide systematic and methodical answers to empirical questions and to incorporate these answers in theological thought. For instance, when and how do modern people have religious experiences, which religious attitudes have an impact on their individual and social life, how do they participate in the life of the church community, and how does the relation between church and society take shape in ordinary life ? It is important not to leave the research on these issues to the social sciences alone, but try to formulate, analyse and answer these questions ourselves from a distinctive theological point of view. This standard work contains a fundamental epistemological and methodological theory of empirical theology. On the basis of empirical methodology and with the help of empirical tools, a theological theory is developed. On this theory, many methodological-technical insights and statistical instructions are based.