Classifications. On philosophers and librarians

Consider the following argument: (Premise 1) If a librarian is a classifier and (Premise 2) a librarian classifies (among the other things) the documents of a library, and (Premise 3) to classify documents is equivalent to classifying the objects of a knowledge base, but (Premise 4) to classify the objects of a knowledge base is equivalent to producing an ontology, or is equivalent to doing some ontological engineering, then (Conclusion) a classifier– i.e. a librarian–is an ontologist. The same train of thought can be followed for those disciplinary experts who support librarians in activities like classification. Thus, librarians and experts are classifiers, and if classifiers are ontologists, librarians and experts are ontologists. Here the problem arises: which specific kind of ontology is in the librarian’s mind? Which one in the expert’s mind? We argue that the librarians’ ontology is completely different from the expert’s. Experts’ ontology is a thematic ontology, librarians’ ontology is generalistic. This conclusion is particularly clear in the philosophical case.