The general theory of what exists most fundamentally is sometimes known as “first philosophy”! The ontology of scientific realism could plausibly be developed to have such a role. As a first philosophy, it would have important implications for most kinds of enquiries. But the ontology of scientific realism, despite its name, may have less relevance to science itself than to other areas. For the metaphysics has been developed out of science, specifically to accommodate the developments that have occurred in this area. Practising scientists are unlikely to be familiar with many of the concepts employed in developing this ontology. Nevertheless, it is one that any scientific realist should be able to accept, and it makes good sense of the nature and structure of scientific knowledge: better, I claim, than any other ontology that has been developed so far. The theory is, perhaps, more likely to be influential in fields that have not been used as a basis for its development: in mathematics, for example, or in moral and political philosophy. For these areas, too, have their onto-logical presuppositions, and some of them are apparently contrary to the tenets of scientific realism. In this chapter, we shall examine some of these presuppositions, and consider how studies in these areas might be accommodated within a scientific realist metaphysical framework.

Realism in mathematics

As a philosopher of science I was always taught to believe that mathematics was essentially different from any of the sciences. Its truths were necessary, and therefore not in need of truthmakers.