Methodological stance
Wagner stresses that the methods must be adapted to the problems at hand and the different levels of scientific investigation. The different levels of study include: (1) the development of adequate concepts capturing the essential properties of economic phenomena; (2) explaining the present state and the development of those phenomena in terms of a combination of psychological motifs and structural conditions; (3) normative economic reasoning determining socially desirable developments; and (4) implementation problems regarding those desirable changes (see, for example, Wagner 1886: 124-8).
Notice that the distinction of positive and normative economics is generally deemed useful for public economics, as is the recognition of the specificities of implementation. Conceptual analysis nowadays does not command as much respect, yet Wagner employs it effectively, for example, regarding collective wants/goods. Levels (1) to (4) prepare the stage for a research architecture in which economic theory, political philosophy, empirical study, and institutional details play specific roles.