Already at the beginning of his scientific career Stichweh began to work on a research program which makes use of the conceptual repertoire of sociological differentiation theory for writing a structural history of the modern system of science and of the system of European universities since the Reformation. His first two books (on 18^th/19^th century physics and on state formation and universities in early modern Europe) were in this field. Stichweh will again intensify research on these subjects in coming years, in a big project which will try to explain the growth of the scale of science and the genesis and expansion of scientific problems since 1750 by looking at the interrelations of science with the function systems in its societal environments.

A second complex of problems central for Stichweh is his work on the evolution of world society. This line of research combines the interest in an original theory of sociocultural evolution with a macrohistory of human societies. This sociological history extends from the settlement of all natural spaces on earth by descendants of the same small group of hominids (Homo Sapiens) up to contemporary world society based on functionally specialized global communication systems. This is furthermore connected to his writings on the social history and historical semantics of strangers which were perceived in nearly all societies as an external source of ‘irritations’.

Thirdly, Stichweh works in the research group he directs in the ‘Forum Internationale Wissenschaft’ at Bonn on a theory of political regimes in the contemporary world. This theory postulates a bipolarity of democratic and authoritarian regimes as two variants of modernity. It traces back this bipolarity to the availability of a worldwide population of elementary political structures and processes of which both types of regimes make selective use for structure formation in building their respective nations or empires. Specifically modern is the inclusion of everyone into things going on in the political system and therefore the sociological theory of inclusion/exclusion is of especial relevance for this research.