Philosophers of science differ in their views concerning the subject matter of science, that is, what theorems are about and to what they refer. These problems are of an ontological nature. Some kind of ontology underlies every language of sciences. This discipline is concerned with "the general principles of being", with what exists, the nature of what exists, types of entities, etc. The ontology of the language of science manifests itself in that language, if only in the syntax of that language, in the kinds of expressions used in that language and in the syntactic categories assigned to them. The idea that language determines an ontology has been emphasized in Poland by Roman Suszko.