ABSTRACT
This chapter focuses on the proposal of Rudolf Carnap, one of the traditional supporters of the project of the unity of science. His suggestions will shed some light on the conception of reality that supports the original proposal of formal unification. The chapter describes the proposal of Brian Ellis about scientific essentialism, a position that corresponds to a unification project based on metaphysical assumptions. Keeping in line with the empiricist tradition, Rudolf Carnap tries to show that it is possible to use a language referring to abstract entities without embracing a strong ontological commitment. In Carnap's view, the acceptance of a linguistic framework is a practical, rather than a theoretical, question. In contrast to the proposal just outlined, Dupre's perspective of promiscuous realism is based on what he calls ontology of common sense, one which is strongly pluralistic. Dupre affirms that there are no general criteria for individuating kinds.
