Industrial Engineering/Operations Management modeling process entails a series of research paradigm decisions to be made as to (1) what the reality domain is - ontology, (2) how the problem domain is to be defined and theorized - epistemology, and (3) which solution domain is to be considered – methodology; and all three being based on axiological assumptions entailing ethical concerns. These paradigm-related decisions need to be based on a series of sound reasoning activities. In this regard, three types of reasoning – abductive, deductive and inductive – will be discussed in connection with a scheme of Operational Research/Management Science modeling process.