Realismo y antirrealismo en la concepción semántica de las teorías científicas

Abstract

Bas van Fraassen, one of the most energetic defenders of the semantic conception of scientific theories, has recently held that while scientific theories can be identified through their models they cannot be identified with them (van Fraassen [1985], cf. this volume). In this paper I want to discuss the content and implications of this idea. I hold that it reveals a confusion present in some of van Fraassen’s previous works, and also that it now shows a commitment to a view compatible with a form of realism. I go on to argue that the confusion at issue is also present in Pérez Ransanz’s conception of scientific theories, according to what she expressed in her debate with van Fraassen.
 I stress the idea that there are at least three ways in which the notion of “model” can be used, which are relevant in philosophy of science for the analysis of the structure and function of scientific theories:
 1) model in the sense of a structure that satisfies a set of conditions of definition; I refer to this type as logical models;
 2) sentential models; and
 3) iconic models.
 For types 2) and 3) I follow Harré [1970] with some modifications which I consider adequate for the analysis of science 1 wish to defend:
 Sentential Models. Let T and T’ be two sets of sentences; T’ is a sentential model of T if and only if for every p in T there is a q in T’ such that if q is acceptable for an epistemic community, i.e. q is objective, then p is supposed to be true, i.e. acceptable for any rational being. (Cf. Olivé [unpublished] for an explication of the notions of objectivity and truth here assumed.)
 Iconic Models. M is an iconic model of N, if and only if it is possible to construct two sets of sentences, T’ and T, such that T’ describes M, T describes N and T’ is a sentential model of T. M and N are either abstract objects or objects of possible experience.
 Thus the same structure can play the role of a logical model or of an iconic model. The very same structure, from the perspective of satisfaction of certain conditions of definition plays the role of a logical model. But seen from the perspective of its capacity to represent another object, it plays the role of an iconic model.
 Van Fraassen’s recent declarations have made explicit that he considers theories as constituted by structures which certainly play the role of both logical and iconic models. In this sense he adopts as a matter of fact a realist position, namely that there is an empirical world which is independent of the theories and conceptual frameworks used to conceptualize it, and also that theories are constituted by structures that play the role of iconic models.
 I further contend that Pérez Ransanz unduly stresses the logical role of models and overlooks their iconic role. This arises out of her emphasis in that scientific theories must be seen as sets of structures that satisfy certain conditions of definition, and also from her idea that intended applications of theories must he seen as parts of the very same theories.
 From my own point of view, an empirical theory has built into itself the claim that it can he applied to the empirical world. In this sense applications must he seen as part of the empirical world, not as parts of theories. It is true, however, that such applications involve first of all the construction of models, which are abstract entities. Finally, I discuss Pérez Ransanz’s ideas as to the empirical basis for theory testing. The problem is that she regards applications as idealizations of empirical systems, thus as models, and hence as parts of theories. So, if the empirical basis is constituted by applications, but in turn these are seen as parts of theories, she is committed to the view that theories must be tested against structures which are constitutive parts of themselves.