Models and analogies in science

Science makes extensive use of models, i.e. simplified or idealized representations of the systems found in the physical world. Models fall into at least two categories: mathematical and physical models. In this paper, we focus attention mainly on the latter, trying to show that they are essential tools not only of the scientific description of the world 'out there', but of man's cognition of things, especially things not directly accessible to the senses. The spring-and-ball (SB) model of chemistry is a most instructive example of a physical model. In other disciplines, from cosmology to physiology, models are used that are of the same kind or play the same role. It is concluded that physical models are objects which belong to the world accessible to man's direct experience, often constructed ad hoc and possibly idealized. They serve as referents for analogies, which appear to be indispensable in most aspects of scientific theorizing, especially for the understanding of the submicroscopic levels of reality.