Merton’s concepts of middle-range theories (MRTs) and grand theories (GTs) are widely mentioned in information systems (IS) theorizing literature. On one hand, numerous IS authors claim that MRTs are common in IS or that design science theories are MRTs. On the other hand, others report that too much focus is placed on GTs (instead of MRTs) in IS. Moreover, MRTs and GTs have acquired a normative role in IS. Given such disagreements and the normative role of MRTs and GTs, there is a need to examine what Merton’s GT and MRT are. The aim of this paper is to start such a discussion by providing an interpretation of Merton’s GT and MRT. We contest many IS views on Merton. We also suggest that Merton’s MRT should be revised and clarified to account for developments in natural sciences and the philosophy of science.