The continuity thesis of the Poznań school threshold model of the growth of scientific knowledge is considered in the light of the example of Van der Waals' and Boyle-Mariotte's laws. It is argued - using both traditional logical means and the structuralist reconstruction of the example - that the continuity thesis does not hold. A distinction between 'a historical and a systematic point of view' is introduced and it is argued that the continuity thesis of the threshold model presupposes the (...) systematic point of view. However, looking at matters from the systematic point of view need not yield the original theory, looked at from the historical point of view. Applied to the case of Van der Waals/Boyle-Mariotte laws, it turns out that the latter law is not a true idealizing special case of the former, contrary to the continuity thesis. The structuralist analysis of the example indicates that Boyle-Mariotte's law is a false factual law from the historical point of view. However, viewed from the systematic point of view, Boyle-Mariotte's law turns out to be a law which is expandable, adding the relevant new concepts, to an idealized version of Van der Waals' law. This idealizing version of Van der Waal's law in turn is a structuralist specialization of the (general) Van der Waals' law. (shrink)

The concept of Galilean Idealization is based on a pragmatically grounded relation between universes of so-called real and idealized entities. The concept was developed in the course of a critical discussion of different explications of the concept of idealization (e.g. by W. F. Barr, C. G. Hempel and L. Nowak), these being attempts to specify sufficient syntactic and semantic criterions for idealization. But this line of argument shall not be followed here. Instead, first the concept of Pragmatic Idealization, and as (...) its special case the Galilean one, is presented (1.) and certain aspects of the application of an idealized theory are discussed (2.). Then, working within the Strucuralist View of theories, definitions of the idealized variants of the diachronic theory-element and theory-net are presented (3.). (shrink)