Matthias Neuber

Rudolf Carnap’s role in the debate over scientific realism is fairly unclear. In a certain sense, Carnap must be regarded as the one who rendered the whole issue irrelevant. However, it cannot be ignored that Carnap sometimes spoke of himself as an ‘empirical realist.’ So the question to be answered is: in what sense, if at all, did Carnap play a constructive role in the scientific realism debate. It is the aim of the present paper to tackle this question by investigating the relationship between Carnap’s approach toward the realism issue, on the one hand, and the realist positions defended by his logical empiricist fellows Hans Reichenbach and Eino Kaila, on the other. It will be shown that Carnap agreed with Reichenbach that realism has essentially to do with language, but that he disagreed with him over the significance of probability in defending the scientific realist stance. My point will be that realism is not a ‘problem of language.’ Furthermore, it will be argued that Carnap was correctly criticized by Reichenbach for neglecting the role of probability in science. Nevertheless, what can be learned from Carnap’s approach toward the realism issue is that scientific realism cannot be defended in the way that Reichenbach himself suggested, namely by arguing inductively for the adequacy of the realistic ‘language form.’ Rather, scientific realism can only be defended on the ground that language itself is dependent on the ‘structure of the world.’ And this is exactly the point where, eventually, Kaila will enter the scene.

Scientific realism is the view that the theoretical entities of science exist. Atoms, forces, electromagnetic fields, and so on, are not merely instruments for organizing observational data but are real and causally effective. This view seems to be hardly compatible with the logical empiricist agenda: As common wisdom has it, logical empiricism is mainly characterized by a strong verification criterion of meaning, i.e., by the project of defining the meaning of theoretical terms by virtue of the meaning of purely observational terms. However, it has been largely ignored by the historians of logical empiricism that there indeed existed a realist faction within the logical empiricist movement.