In this work, it is argued that one of the foundations of NiklasLuhmann’s theory of social systems, namely that it has no ontology, would prevent the elaboration of explanations in sociology. Because the theory has a formal-logical foundation, which does not presuppose ontology, there are insurmountable obstacles to achieving this objective. For this reason, it is valid to wonder about the merit of a theory that, after 20 years, insists on not aligning itself with ontological premises in a robust way (...) and suggests, therefore, a refusal to integrate sociology within the set of factual sciences. However, we think that the richness of Luhmann’s work allows a dialogue with the mainstream of contemporary theoretical practice. Three rules about what “should not be done” are revalidated from this analysis to philosophically base a theory in sociology and a key suggestion to overcome the problem of explanation in Luhmann’s sociology: social science seeks and directs its activity towards discovery and the use of substantive, real distinctions that also enrich the factual content of statements about social reality. (shrink)