Who is a Modeler?

Standard accounts of the nature of scientific theories ignore a crucial distinction between modeling and other types of theory construction. This conflation badly distorts important contrasts among the goals, products, and practices of modelers and non-modelers. We can see this difference intuitively when we consider the approaches of theorists such as Vito Volterra and David Marr on one hand, and Charles Darwin and William James on the other. Volterra and Marr were modelers; Darwin and James were not. This paper develops an account of theory construction capable of capturing this distinction. This account distinguishes between modeling and non-modeling along two dimensions: the nature of the theory--world relationship and the norms which govern the construction of theoretical representations. By differentiating modeling from other forms of theorizing, we can gain greater insight into the process of theory construction, effective strategies of idealization, and what is really at issue in certain debates between theorists and experimentalists.