Abstract

idea of a mechanical balance, described the volume of exchange of various aggregated commodities, weighted by their price, balanced against the quantity of money in the economy, weighted by the money’ s rate of circulation. Another family of models addressed issues about the gold standard and bimetallism by thinking of quantities of gold and silver as liquids in different connected reservoirs representing, alternatively, bullion and minted coin, and the way the liquids/metal/currency in one reservoir will ¯ ow into others if the level in one becomes higher than in another. Morgan sets out the ways in which Fischer developed these models in response to both theoretical and practical issues of the day. In the process we see how the activity of building models can address relations which are very imperfectly understood, revealing previously unappreciated causal interconnections. For example, Gresham’ s law is revealed as just one facet of a much more complex network of interconnected variables, and the models help to make clear the conditions under which this law does and does not apply. Also illustrated are ways in which such models can be illuminating about the underlying mechanisms even though the models in question involve extreme idealizations and are extremely limited in practical application because they require parameters which cannot be independently measured. In this respect these examples provide cases in which models would appear to facilitate theory development and articulation more than mediation between preexisting theory and the world. Different readers, because they will be looking for different things, will themselves offer widely different evaluations of these essays, individually and collectively. In my own evaluation this collection provides a wonderful resource of much needed detail for use in the effort of all interpreters of science to move beyond past problematic oversimpli® cations. Accounts such as the positivist and semantic descriptions of theories can themselves be seen as highly idealized models, and as such do indeed bring out important features of the ways in which we theorize about the world..