Reflections on the structure of the language of physics

The aim of this paper is to discuss how far physics differs from mathematics, and if a philosophy of science which uses mathematics or logics asa a model for physics would be unable to be aware of many important features of that natural science. 1. Many functions in physics differ from those of mathematics in being functional dependencies and in having a lawlike character. 2. Physical quantities have the character of 'determinables', sets of special entities which are presupposed by physical theories. 3. One may suspect that physics also could not be formulated in an extensional language. This cannot be true, however, since every language can be translated into an extensional version. Nevertheless the existence of determinables in physics shows that physics does not only talk about concrete entities like space, time, spacetime, and particles, but also about values of abstract sets like determinables, and that it thus acknowledges their existence.