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This thesis examines the methodological issues raised by the inclusion of the physical dimension of the economic process in economic theory. To this end, it focuses on the thermodynamic conception of the economy, developed in particular by Nicholas Georgescu-Roegen and Robert Ayres. More precisely, this thesis studies the way in which the thermodynamic conception of the economy is embodied in two formal representations of production, the neo-thermodynamic theory and the flow-fund theory, and how these approaches confront the neoclassical theory of resources. In order to understand the methodological issues associated with these various theories, the thesis focuses on issues related to modeling and interdisciplinarity. It shows that neoclassical resource theory and neo-thermodynamic theory share a common conception of modeling, which is reflected in the use of aggregate production functions. However, this representation of production proves inadequate to account for the physical dimension of production, both conceptually and empirically. On the contrary, the flow-fund theory constitutes a radical methodological break with the aggregate production function. It is better able to grasp the physical dimension of production from a conceptual point of view, but suffers from a lack of application. Overall, the thesis shows that methodological issues related to modeling should receive more attention when it comes to accounting for the physical dimension of the economic process.

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This thesis examines the methodological issues raised by the inclusion of the physical dimension of the economic process in economic theory. To this end, it focuses on the thermodynamic conception of the economy, developed in particular by Nicholas Georgescu-Roegen and Robert Ayres. More precisely, this thesis studies the way in which the thermodynamic conception of the economy is embodied in two formal representations of production, the neo-thermodynamic theory and the flow-fund theory, and how these approaches confront the neoclassical theory of resources. In order to understand the methodological issues associated with these various theories, the thesis focuses on issues related to modeling and interdisciplinarity. It shows that neoclassical resource theory and neo-thermodynamic theory share a common conception of modeling, which is reflected in the use of aggregate production functions. However, this representation of production proves inadequate to account for the physical dimension of production, both conceptually and empirically. On the contrary, the flow-fund theory constitutes a radical methodological break with the aggregate production function. It is better able to grasp the physical dimension of production from a conceptual point of view, but suffers from a lack of application. Overall, the thesis shows that methodological issues related to modeling should receive more attention when it comes to accounting for the physical dimension of the economic process.

This paper provides a theoretical and methodological account of an important controversy between neoclassical resources economics and ecological economics, from the early 1970s to the end of the 1990s. It shows that the assumption of unbounded resources productivity in the work of Solow and Stiglitz, and the related concepts of substitution and technical progress, rest on a model-based methodology. On the other hand, Georgescu-Roegen's assumption of thermodynamic limits to production, later revived by Daly, comes from a methodology of interdisciplinary consistency. I conclude that neither side provided a definitive proof of its own claim because both face important conceptual issues.

From a historical and methodological perspective, this paper focuses on empirical work on energy based on the aggregate production function from the early 1970s to the late 2000s. It first discusses the standard neoclassical approach, and in particular the controversy over the substitutability between capital and energy. He then discusses the thermodynamic approach, which is more oriented towards explaining long-term growth. He shows a continuity in the methodological issues raised by this work. At the theoretical level, the aggregate production function offers little conceptual support for the physical aspects of the production process. At the empirical level, the results of the estimations of production functions with energy raise questions. In the neoclassical framework, the estimation is carried out indirectly via the cost function, so that the result is overdetermined by the assumption of marginal productivity wages. The thermodynamic approach, on the other hand, uses direct estimation, which encounters no less important statistical problems. If these difficulties concern the aggregate production function in a more general way, the energy question reveals them in a very striking way.

This paper provides a theoretical and methodological account of an important controversy between neoclassical resource economics and ecological economics from the early 1970s to the end of the 1990s. It shows that the assumption of unbounded resource productivity in the work of Solow and Stiglitz–and the related concepts of substitution and technical progress–rest on a model-based methodology. On the other hand, Georgescu-Roegen’s assumption of thermodynamic limits to production, later revived by Daly, comes from a methodology of interdisciplinary consistency. I conclude that neither side provided a definitive proof of its own claim because both face important conceptual issues.

Despite his early contribution to the rise of mathematics in economics, Georgescu-Roegen's later methodological criticism of models has received little attention from historians and philosophers of economics. This paper attempts to fill this gap following two lines. First, I examine his explicitly methodological claims and connect them with related topics in economic methodology. Building on the distinction between dialectical and arithmomorphic concepts, I characterise his approach to theory-making as a three steps process of idealisation, isolation and arithmetisation. In this framework, models perform two functions, checking for logical consistency and facilitating understanding, which can be related to the idea of modelling as theorising. I then confront these general principles with Georgescu-Roegen's flow-fund model of production. I use the methodology as a reading grid of this theory, while examining its limits and complementary principles in practice. This shows a great deal of consistency, where idealisation provides conceptual foundations, isolation determines the relevant problems, and models are built according to structural consistency. The two functions of models are then illustrated by the logical derivation of older principles formulated by Babbage and Smith, and the understanding of the different organisational patterns of production. But some slightly different functions also appear when specific configurations of the model enable to check the conceptual consistency of other theories, or the understanding provided by the model contributes to the formation of new concepts. Hence, the consistency and the complementarity between Georgescu-Roegen's methodology and practice of theory-making provide interesting insights and a useful background for further investigations.

This paper proposes a historical and epistemological account of one of the key controversy between natural resources economics and ecological economics, lasting from early 1970s to the end of 1990s. It shows that the theoretical disagreement on the scope of the economy's dependence to natural resources, such as energy and minerals, has deep methodological roots. On one hand, Solow's and Stiglitz's works are built on a “model-based methodology”, where the model precedes and supports the conceptual foundations of the theory and in particular the assumption of “unbounded resources productivity”. On the other hand, Georgescu-Roegen's counter-assumption of “thermodynamic limits to production”, later revived by Daly, rest on a methodology of “interdisciplinary consistency” which considers thermodynamics as a relevant scientific referent for economic theory. While antagonistic, these two methodologies face similar issues regarding the conceptual foundations that arise from them, which is a source of confusion and of the difficult dialogue between paradigms.

From the end of the 1960s onwards, Nicholas Georgescu-Roegen developed a critique of standard economics and the foundations of his "bioeconomic" perspective around the law of entropy. After providing a historical and epistemological introduction to the issues surrounding the law of entropy, we examine the pivotal role played by this law in this theoretical turn.