Realism, Theory-Equivalence and Underdetermination of Theories

Abstract

The focus of this chapter is the realism-antirealism debate in philosophy of science. The two central doctrines of scientific realism, viz., (i) central terms in mature theories refer to existing things, and (ii) scientific theories are approximately true, are discussed. In so far as ‘term’ is understood as ‘general term’ this doctrine conflicts with nominalism and is thus rejected. The other doctrine should however be accepted also by empiricists, it is argued.

The underdetermination argument, generally thought to be a great hurdle for scientific realism, takes for granted that two empirically equivalent theory formulations really express different theories. This assumption can be countered by an argument taken from Quine, showing that empirically equivalent theory formulations always can be translated to each other. Hence, one may hold that empirically equivalent theories are mere different theory formulations of the same theory. Thus both empiricists and scientific realists can reject the underdetermination argument. The debate about versions of structural realism is then discussed. The notion that a mere structure, thought of as being invariant under isomorphisms, could represent the physical world is critised on the basis of Löwenheim-Skolem’s theorem.

The ontology of quantities is the next topic. The crucial problem is identity criteria for quantities; since they are additive, one can for example ask how many forces are acting on certain accelerating body? Is it one, or several? If the latter is the correct answer, what is the true decomposition of the vector sum? The conclusion is that quantities are not real things, quantitative predicates have extensions but no references.