摘要
The model-based enquiry depends on the form in which models are formulated and represented. When economists select a model as an efficient reasoning tool, they may first consider the type of model whose inherited epistemic virtue and reasoning rules best fits their needs. This chapter studies the dependence between the different forms of models and scientific knowledge by considering a particular form of model, that is, the diagram. This chapter draws from the history of location theory, which provides us with an example of how economists reasoned with diagrams, how their particular geometric shapes became an idealized landscape, and how they reasoned into them to account for actual spatial patterns of economic activity providing the opportunity for policy advice. Three different diagrams are examined: Johann Heinrich von Thünen’s concentric rings of agricultural land use, Alfred Weber’s triangles of industrial locations, and Walter Christaller’s hexagons of market area.