Tinbergen (1988) describes his method of conducting economic research. In contrast to Dopfer (1988), the subject of mechanics is avoided, and the method deals only with economics. The purpose of economic research is seen as either: 1. an attempt to explain an economic phenomenon, or 2. the recommendation of an economic policy or structure. No use is made of any philosophy of science concepts. An important characteristic of Tinbergen's views is that he deals with qualitative and quantitative aspects of economic research. The difference between quantitative and qualitative problems is that the former are solved completely only after measurement and mathematical solution with the aid of a model, whereas the latter do not require the tools of measurement and mathematical solution. In a reply, Dopfer comments on Tinbergen's belief that both quantitative and qualitative research is important in economics. He notes that such an insight can have various interpretations, depending on the viewpoint of the researcher.