Realism and the nature of theory: A lesson from J.H. von Thünen for economists and geographers

It is argued that J H von Thuënen was a realist who deliberately used unrealistic assumptions to pursue a true account of a major aspect of the determination of agricultural land-use patterns. The assumptions of the simplest model of concentric rings are examined to show that this highly unrealistic model deserves a realist interpretation: the idealising assumptions serve the purpose of neutralising the impact of a number of factors on the land-use pattern and thereby help focus on the causal contribution of one major factor, namely distance from the market. It is von Thuënen's conviction that this factor and its causal contribution are real rather than fictional, and that his basic model truthfully captured them. The potential truth of von Thuënen's simplest model does not require that its assumptions are true nor that the representation of the resulting land-use pattern is true. This reading of von Thünen's theory is contrasted with the traditional fictionalist 'as-if' interpretation of Der isolierte Staat espoused by Hans Vaihinger, Peter Hall, and others. It is pointed out that economists and geographers both hold notions of realism that fail to accommodate von Thünen's realism. Although economists tend to conflate realism and realisticness and therefore fail to understand that realism is compatible with the use of unrealistic assumptions, human geographers have adopted highly specific ideas of realism that fail to do justice to von Thünen's theory. Because much of theorising in both disciplines follows the Thünian strategy, there is an important lesson to be learnt both for supporters and for opponents of that strategy.